Strategy Based Diagnostics
- Perform the «Diagnostic Starting Point - Vehicle»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-starting-point-vehicle) before using the symptom tables, if applicable.
- Review the system operations in order to familiarize yourself with the system functions. Refer to «Disassembled Views»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-component-locator) , , «Engine Component Description»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-description-and-operation) , , and «Lubrication Description»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-description-and-operation) , , and to the «Drive Belt System Description»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-description-and-operation__drive-belt-system-description) .
All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system problem. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer to Strategy Based Diagnosis .
Visual/Physical Inspection
- Inspect for aftermarket devices which could affect the operation of the engine.
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
- Check for the correct oil level, proper oil viscosity, and correct filter application.
- Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, ambient temperature, engine temperature, amount of engine warm-up time, and other specifics.
- Compare the engine sounds, if applicable, to a known good engine and make sure you are not trying to correct a normal condition.
Intermittent
Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom
- «Base Engine Misfire without Internal Engine Noises»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__base-engine-misfire-without-internal-engine)
- «Base Engine Misfire with Abnormal Internal Lower Engine Noises»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__base-engine-misfire-with-abnormal-internal)
- «Base Engine Misfire with Abnormal Valve Train Noise»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__base-engine-misfire-with-abnormal-valve)
- «Base Engine Misfire with Coolant Consumption»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__base-engine-misfire-with-coolant-consumption)
- «Base Engine Misfire with Excessive Oil Consumption»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__base-engine-misfire-with-excessive-oil)
- «Engine Compression Test»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__engine-compression-test)
- «Engine Noise on Start-Up, but Only Lasting a Few Seconds»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__engine-noise-on-start-up-but-only)
- «Upper Engine Noise, Regardless of Engine Speed»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__upper-engine-noise-regardless-of-engine)
- «Lower Engine Noise, Regardless of Engine Speed»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__lower-engine-noise-regardless-of-engine)
- «Engine Noise Under Load»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__engine-noise-under-load)
- «Engine Will Not Crank - Crankshaft Will Not Rotate»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__engine-will-not-crank-crankshaft)
- «Oil Pressure Diagnosis and Testing»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__oil-pressure-diagnosis-and-testing)
- «Oil Leak Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__oil-leak-diagnosis)
- «Drive Belt Rumbling and Vibration Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures)
- «Drive Belt Falls Off and Excessive Wear Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures)
- «Drive Belt Tensioner Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-diagnostic-information-and-procedures__drive-belt-tensioner-diagnosis)
Base Engine Misfire without Internal Engine Noises
| Condition | Action |
|---|---|
| Abnormalities (severe cracking, bumps or missing areas) in the accessory drive belt. Also worn, damaged, or misaligned accessory drive components or excessive pulley runout. | Abnormalities in the accessory drive belt and/or components may cause engine RPM variations, noises similar to a faulty lower engine and also lead to a misfire condition. A misfire code may be present without an actual misfire condition. Inspect the accessory drive components. Repair or replace all damaged components. |
| Loose and/or damaged crankshaft balancer | A misfire code may be present without an actual misfire condition. Inspect crankshaft balancer and balancer bolt. Repair or replace all damaged components. |
| Loose torque converter bolts | A misfire code may be present without an actual misfire condition. Inspect torque converter bolts and flywheel. Repair or replace all damaged components. |
| Loose and/or damaged flywheel | A misfire code may be present without an actual misfire condition. Inspect flywheel and flywheel attaching bolts. Repair or replace all damaged components. |
| Restricted exhaust system | A severe restriction in the exhaust flow can cause significant loss of engine performance and may set a misfire code. Possible causes of restrictions include collapsed or dented pipes, plugged mufflers and/or catalytic converters. Repair or replace all damaged components. |
| Air in fuel system | Inspect fuel filter, fuel system for leaks and/or restrictions. Repair or replace all damaged components. |
| Bent and/or worn valve pushrod | Inspect valve pushrod and valve rocker arm. Repair or replace all damaged components. |
| Sticking valve | Carbon on the valve stem or valve seat may cause the valve to stick. Inspect valves and valve guides. Repair or replace all damaged components. |
| Damaged or misaligned timing gears | Inspect timing gears. Replace all damaged components. |
| Worn or faulty camshaft lobes | Inspect camshaft lobes. If damaged replace camshaft and all lifters. |
| Excessive piston-to-cylinder bore clearance | Perform cylinder leak down and compression tests. Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
| Faulty cylinder head gaskets and/or cracking or other damage to the cylinder heads and engine block cooling system passages. (Coolant consumption may or may not cause the engine to overheat.) | Perform cylinder leak down and compression tests. Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
| Overfilled Crankcase | Check engine oil level with vehicle on a level surface. Correct any overfilled condition. Inspect for fuel leaks into the crankcase. Refer to Fuel in Engine Oil . Repair any fuel leaks. |
Base Engine Misfire without Internal Engine Noises
Base Engine Misfire with Abnormal Internal Lower Engine Noises
| Condition | Action |
|---|---|
| Abnormalities (severe cracking, bumps or missing areas) in the accessory drive belt. | Abnormalities in the accessory drive belt and/or components may cause engine RPM variations, noises similar to a faulty lower engine and also lead to a misfire condition. A misfire code may be present without an actual misfire condition. Inspect the accessory drive components. Repair or replace all damaged components. |
| Worn, damaged, or misaligned accessory drive components or excessive pulley runout | A misfire code may be present without an actual misfire condition. Inspect the accessory drive components. Repair or replace all damaged components. |
| Loose and/or damaged crankshaft balancer | A misfire code may be present without an actual misfire condition. Inspect crankshaft balancer and balancer bolt. Repair or replace all damaged components. |
| Loose torque converter bolts | A misfire code may be present without an actual misfire condition. Inspect torque converter bolts and flywheel. Repair or replace all damaged components. |
| Loose and/or damaged flywheel | A misfire code may be present without an actual misfire condition. Inspect flywheel and flywheel attaching bolts. Repair or replace all damaged components. |
| Excessive piston-to-cylinder bore clearance | Perform cylinder leak down and compression tests Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
| Excessive crankshaft thrust bearing clearance | Severely worn thrust surfaces on the crankshaft and/or thrust bearing may permit for and aft movement of the crankshaft and create a misfire code without an actual misfire condition. Inspect the crankshaft end play and crankshaft thrust bearings. Repair or replace all damaged components. |
| Overfilled crankcase | Check engine oil level with vehicle on a level surface. Correct any overfilled condition. Inspect for fuel leaks into the crankcase. Repair any fuel leaks. |
Base Engine Misfire with Abnormal Internal Lower Engine Noises
Base Engine Misfire with Abnormal Valve Train Noise
| Condition | Action |
|---|---|
| Loose, worn or damaged rocker arm | Inspect valve rocker arm and rocker arm shaft. Repair or replace all damaged components. |
| Loose valve rocker arm attachments | Inspect valve rocker arm and rocker arm shaft. Repair or replace all damaged components. |
| Worn or damaged pushrods | Inspect the pushrods for excessive wear. Inspect the pushrods for bent condition. Inspect the pushrods for broken tip. Replace pushrod if any damage is found. |
| Broken valve springs | Inspect valve springs. Repair or replace all damaged components. |
| Worn and/or damaged valve rotator | Inspect valve rotators. Repair or replace all damaged components. |
| Sticking valve | Carbon on the valve stem or valve seat may cause the valve to stick. Inspect valves and valve guides. Repair or replace all damaged components. |
| Worn or faulty camshaft lobes | Inspect camshaft lobes. If damaged replace camshaft and all lifters. |
| Excessive valve lash | Check the valve lash adjustment, and correct if above specifications. Repair or replace all damaged components. |
Base Engine Misfire with Abnormal Valve Train Noise
Base Engine Misfire with Coolant Consumption
| Inspection | Action |
|---|---|
| Special Tools EN 48974 EGR Cooler Pressure Tester Adapter Set EN 48974-20 EGR Cooler Pressure Tester Adapter Set For equivalent regional tools, refer to Special Tools .DEFINITION: Base engine misfire with coolant consumption | |
| Preliminary Inspection | Verify that there are no external coolant leaks. Refer to Loss of Coolant . |
| Isolate Affected Cylinders | NOTE: If coolant is found in any of the right bank cylinders, inspect for a leaking EGR cooler using EN 48974 set -1 and EN 48974-20 set. Coolant may enter the right bank cylinders through the exhaust system after shutdown. Cylinder balance test with scan tool Cooling system pressurization Inspection of glow plugs Compression test Cylinder leakdown test |
| EGR System Inspection | Inspect EGR cooler(s) using EN 48974 set -1 and EN 48974-20 set. Replace the EGR cooler if any problem is found. Inspect EGR cooler bypass valve, if equipped, using EN 48974-20 set. Replace the EGR cooler bypass valve if any problem is found. |
| Cylinder Head Gasket Leakage | Remove cylinder heads of the affected cylinder bank and inspect for damage. Replace components as necessary. |
| Cylinder Head or Engine Block Damage | Inspect the cylinder heads for cracks and warpage. Inspect the cylinder block for damage. Inspect the cylinder block to head mating surface for straightness. Replace components as necessary. |
| NOTE |
|---|
| If coolant is found in any of the right bank cylinders, inspect for a leaking EGR cooler using EN 48974 set -1 and EN 48974-20 set. Coolant may enter the right bank cylinders through the exhaust system after shutdown. |
Base Engine Misfire with Coolant Consumption
Base Engine Misfire with Excessive Oil Consumption
| Condition | Action |
|---|---|
| Worn valve guides | Inspect the valves and valve guides. Repair or replace all damaged components. |
| Worn valve stem oil seals | Inspect the valve stem oil seals. Repair or replace all damaged components. |
| Excessive piston-to-cylinder bore clearance | Perform cylinder leak down and compression tests to determine the cause. Inspect the piston rings for low ring tension, broken or worn rings. Inspect cylinder bore. Repair or replace all damaged components. |
Base Engine Misfire with Excessive Oil Consumption
Engine Noise on Start-Up, but Only Lasting a Few Seconds
| Condition | Action |
|---|---|
| Incorrect oil viscosity | Drain the oil. Install the correct viscosity oil. |
| Excessive piston-to-cylinder bore clearance | Inspect the piston and piston skirt, connecting rod, and cylinder bore. Repair or replace all damaged components. |
| Damaged or faulty oil filter by-pass valve | Inspect the oil filter by-pass valve for proper operation. Repair or replace as necessary. |
Engine Noise on Start-Up, but Only Lasting a Few Seconds
Upper Engine Noise, Regardless of Engine Speed
| Condition | Action |
|---|---|
| Low oil pressure | Insufficient or poor oil supply to valve train. Perform oil pressure test. Repair or replace all damaged components. |
| Improper lubrication to the valve rocker arms | Inspect valve rocker arm and shaft, valve pushrod, oil filter bypass valve, oil pump and pump screen, and engine block oil galleries. Repair or replace all damaged components. |
| Excessive valve lash | Check the valve lash adjustment, and correct if above specifications. Repair or replace all damaged components. |
| Worn pushrod upper end ball | Inspect pushrod end ball. Repair or replace all damaged components. |
| Bent valve pushrod | Inspect valve pushrod and valve rocker arm. Repair or replace all damaged components. |
| Loose, worn or damaged valve rocker arm | Inspect valve rocker arm and rocker arm shaft. Repair or replace all damaged components. |
| Loose valve rocker arm attachments | Inspect valve rocker arm and rocker arm shaft. Repair or replace all damaged components. |
| Broken valve springs | Inspect valve springs. Repair or replace all damaged components. |
| Worn and/or damaged valve spring shims, seats, or keys | Inspect valve spring shims, seats, and keys. Repair or replace all damaged components. |
| Sticking valve | Carbon on the valve stem or valve seat may cause the valve to stick. Inspect valves and valve guides. Repair or replace all damaged components. |
| Missing or improperly positioned lifter guides | Inspect lifter guides. Repair or replace all damaged components. |
| Worn or faulty camshaft lobes | Inspect camshaft lobes. If damaged replace camshaft and all lifters. |
| Worn valve guide | Inspect the valves and valve guides. Repair or replace all damaged components. |
| Damaged or misaligned timing gears | Inspect timing gears. Replace all damaged components. |
Upper Engine Noise, Regardless of Engine Speed
Lower Engine Noise, Regardless of Engine Speed
| Condition | Action |
|---|---|
| Worn accessory drive components (abnormalities such as severe cracking, bumps or missing areas in the accessory drive belt and/or misalignment of the system components.) | Inspect the accessory drive components. Repair or replace all damaged components. |
| Low oil pressure | Insufficient or poor oil supply to crankshaft and connecting rod bearings. Perform oil pressure test. Repair or replace all damaged components. |
| Leaking and/or sticking fuel injection nozzle (A stuck fuel injection nozzle can cause a noise similar to a damaged piston, rod or rod bearing.) | Use the cylinder balance diagnostic procedure to help locate the cylinder that is the source of the noise. If you cannot locate the cylinder that is the source of the noise, diagnose the engine for mechanical damage. If it has been determined that the fuel injection nozzle is causing the noise, replace the fuel injection nozzle. |
| Loose and/or damaged crankshaft balancer | Inspect crankshaft balancer and balancer bolt. Repair or replace all damaged components. |
| Loose torque converter bolts | Inspect torque converter bolts and flywheel. Repair or replace all damaged components. |
| Loose and/or damaged flywheel | Inspect flywheel and flyweel attaching bolts. Repair or replace all damaged components. |
| Excessive piston-to-cylinder bore clearance | Inspect the piston, piston rings and cylinder bore. Repair or replace all damaged components. |
| Excessive piston pin-to-bore clearance | Inspect the piston, piston pin, and the connecting rod. Repair or replace all damaged components. |
| Misaligned or bent connecting rod | Inspect connecting rod and connecting rod bearings. Repair or replace all damaged components. |
| Excessive connecting rod bearing clearance | Inspect the connecting rod bearings, connecting rods, crankshaft and crankshaft journals. Repair or replace all damaged components. |
| Excessive crankshaft bearing clearance | Inspect the crankshaft bearings and crankshaft journals. Repair or replace all damaged components. |
| Oil pump pickup tube or screen bent or loose | Inspect the oil pump pickup tube and/or screen. Repair or repalce all damaged components. |
Lower Engine Noise, Regardless of Engine Speed
Engine Noise Under Load
| Cause | Correction |
|---|---|
| Low oil pressure | Insufficient or poor oil supply to components. Perform oil pressure test. Repair or replace all damaged components. |
| Loose torque converter bolts | Inspect the torque converter bolts and flywheel. Repair or replace all damaged components. |
| Loose and/or damaged flywheel | Inspect the flywheel and flywheel attaching bolts. Repair or replace all damaged components. |
| Excessive piston-to-cylinder bore clearance | Inspect the piston rings for low ring tension, broken or worn rings, inspect cylinder bore. Repair or replace all damaged components. |
| Excessive crankshaft thrust bearing clearance | Inspect the crankshaft end play and crankshaft thrust bearings. Repair or replace all damaged components. |
| Excessive crankshaft bearing clearance | Inspect the crankshaft bearings and crankshaft journals. Repair or replace all damaged components. |
Engine Noise Under Load
Engine Will Not Crank - Crankshaft Will Not Rotate
| Cause | Correction |
|---|---|
| Seized accessory drive system component | Remove accessory drive belt(s). Remove the glow plugs. Rotate crankshaft by hand at the balancer. |
| Hydraulically locked cylinder Coolant/antifreeze in cylinder Oil in cylinder Fuel in cylinder | Inspect for fluid at glow plug hole. Inspect for broken head gasket(s). Inspect for cracked engine block or cylinder head. Inspect for a sticking fuel injector. |
| Seized automatic transmission torque converter | Remove the engine assembly. The torque converter bolts are not accessible with the engine installed to the transmission. Rotate crankshaft by hand at the balancer or flywheel location. |
| Seized manual transmission | Disengage the clutch. Rotate crankshaft by hand at the balancer. |
| Material in cylinder: Broken valve Piston material Foreign material | Inspect cylinder for damaged components and/or foreign materials. Repair or replace as required. |
| Seized crankshaft or connecting rod bearings | Inspect crankshaft and connecting rod bearings. Repair as required. |
| Bent or broken connecting rod | Inspect connecting rods. Repair as required. |
| Broken crankshaft | Inspect crankshaft. Repair as required. |
Engine Will Not Crank - Crankshaft Will Not Rotate
Coolant in Combustion Chamber
| Inspection | Action |
|---|---|
| Special Tools EN 48974 EGR Cooler Pressure Tester Adapter Set EN 48974-20 EGR Cooler Pressure Tester Adapter Set For equivalent regional tools, refer to Special Tools .DEFINITION: Excessive white smoke and/or coolant type odor coming from the exhaust pipe may indicate coolant in the combustion chamber. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may cause engine component damage. | |
| Preliminary Inspection | Verify that there are no external coolant leaks. Refer to Loss of Coolant . |
| Isolate Affected Cylinders | NOTE: If coolant is found in any of the right bank cylinders, inspect for a leaking EGR cooler or bypass valve, if equipped, using EN 48974 set -1 and EN 48974-20 set. Coolant may enter the right bank cylinders through the exhaust system after shutdown. Cylinder balance test with scan tool Cooling system pressurization Inspection of glow plugs Compression test Cylinder leakdown test |
| EGR System Inspection | Inspect EGR cooler(s) using EN 48974 set -1 and EN 48974-20 set. Replace the EGR cooler(s) if any problem is found. Inspect EGR cooler bypass valve, if equipped, using EN 48974-20 set. Replace the EGR cooler bypass valve if any problem is found. |
| Cylinder Head Gasket Leakage | Remove cylinder heads of the affected cylinder bank and inspect for damage. Replace components as necessary. |
| Cylinder Head or Engine Block Damage | Inspect the cylinder heads for cracks and warpage. Inspect the cylinder block for damage. Inspect the cylinder block to head mating surface for straightness. Replace components as necessary. |
| NOTE |
|---|
| If coolant is found in any of the right bank cylinders, inspect for a leaking EGR cooler or bypass valve, if equipped, using EN 48974 set -1 and EN 48974-20 set. Coolant may enter the right bank cylinders through the exhaust system after shutdown. |
Coolant in Combustion Chamber
Coolant in Engine Oil
| Cause | Correction |
|---|---|
| DEFINITION: Foamy or discolored oil or an engine oil "overfill" condition may indicate coolant entering the engine crankcase. Low coolant levels, an inoperative cooling fan, or a faulty thermostat may lead to an "overtemperature" condition which may cause engine component damage. Contaminated engine oil and oil filter should be changed. Inspect the oil for excessive foaming or an overfill condition. Oil diluted by coolant may not properly lubricate the crankshaft bearings and may lead to component damage. Refer to Lower Engine Noise, Regardless of Engine Speed . Inspect by performing a Cylinder Leak-Down Test. During this test, excessive air bubbles within the cooling system may indicate a faulty gasket or damaged component. Inspect by performing a cylinder compression test. Two cylinders "side-by-side" on the engine block with low compression may indicate a failed cylinder head gasket. Refer to Engine Compression Test . | |
| Faulty cylinder head gasket | Replace the head gasket and components as required. Refer to Cylinder Head Cleaning and Inspection , and Cylinder Head Replacement - Left Side , or Cylinder Head Replacement - Right Side . |
| Warped cylinder head | Replace the cylinder head gasket. Refer to Cylinder Head Replacement - Left Side , or Cylinder Head Replacement - Right Side . |
| Cracked cylinder head | Replace the cylinder head and gasket. |
| Cracked engine block | Replace the components as required. |
| Cylinder head, block, or manifold porosity | Replace the components as required. |
| Leaking engine oil cooler | Replace components as required. |
| Faulty water pump | Replace components as required. |
| Leaking cylinder head cup plug (under rocker cover) | Replace components as required. |
Coolant in Engine Oil
Fuel in Engine Oil
Definition: If fuel is suspected of leaking into the crankcase, the following procedure should be performed to verify the condition.
- Remove the oil level indicator and allow oil to drop onto a clean white paper towel.
- If the oil is diluted with fuel, it will become apparent as the towel wicks the fuel away from the drop of oil on the towel. The fuel will expand out in a ring around the oil droplet.
- If fuel dilution is apparent, refer to «Fuel Leak Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/testing-diagnostics/#engine-controls-and-fuel-66l-lgh-dtc-p204c-to-dtc-p2599-and-diagnostic-information-and-procedures__fuel-leak-diagnosis) , for diagnosis and repair. Inspect the vehicle for aftermarket performance accessories that may cause damage to the injection pump. After repairs are completed, perform the test again to verify the condition is corrected.
- If no fuel dilution is present, verify the oil level and correct as needed.
Turbocharger Whine Noise
| Condition | Action |
|---|---|
| Some whine noise is normal. Compare to a known good vehicle. | |
| Leaking charge air cooler/pipes/hoses | Inspect for leaks in charge air cooler/pipes/hoses using J 46091 Charge Air Cooler Tester. |
| Worn turbocharger bearings | Visually inspect for evidence of compressor wheel to housing contact. If the turbocharger bearings are worn or damaged, inspect for a restriction in the turbocharger oil feed lines/fittings. |
| Intake system leaks or obstructions | With the engine off, pressurize the intake system using J 46091 Charge Air Cooler Tester and inspect for intake manifold leaks. Inspect for obstructions in the intake manifolds. |
Turbocharger Whine Noise
Turbocharger Hissing Noise
| Condition | Action |
|---|---|
| Air inlet leaks or obstructions | Inspect for leaks or obstructions in the turbocharger inlet pipes/hoses. |
| Leaking charge air cooler/pipes/hoses | Inspect for leaks or obstructions in the charge air cooler/pipes/hoses using J 46091 charge air cooler tester |
| Leaking or restricted exhaust system | Inspect for a leak in the exhaust system. Inspect for a restricted exhaust system. |
| Intake system leaks or obstructions | With the engine off, pressurize the intake system using J 46091 charge air cooler tester and inspect for intake manifold leaks. Inspect for obstructions in the intake manifolds. |
Turbocharger Hissing Noise
Turbocharger Oil Leak From Compressor Seal
| Condition | Action |
|---|---|
| IMPORTANT: Oil in the turbocharger air inlet duct,oil on the compressor wheel, and oil throughout the charge air cooler system is normal with a closed PCV system. Do not attempt repairs for this condition. | |
| Restricted air system | Inspect for clogged air filter element or restricted air inlet system. |
| Restricted exhaust system | Inspect for a restricted exhaust. |
| Leaking exhaust system. | Inspect for exhaust manifold leaks. |
| Poor oil drainage from turbocharger | Inspect for restricted turbocharger oil drain pipe. |
| Restricted crankcase ventilation system | Inspect for restricted crankcase ventilation system. |
| Worn internal engine components | Inspect for excessive blowby or engine oil consumption. |
| IMPORTANT |
|---|
| Oil in the turbocharger air inlet duct,oil on the compressor wheel, and oil throughout the charge air cooler system is normal with a closed PCV system. Do not attempt repairs for this condition. |
Turbocharger Oil Leak From Compressor Seal
Turbocharger Oil Leak From Turbine Seal
| Condition | Action |
|---|---|
| Poor oil drainage from turbocharger | Inspect for a restricted turbocharger oil drain pipe. |
| Restricted crankcase ventilation system | Inspect for a restricted crankcase ventilation system. |
| Worn internal engine components | Inspect for excessive blowby or engine oil consumption. |
Turbocharger Oil Leak From Turbine Seal
Engine Compression Test
Special Tools
- J 26999 Compression Gauge
- EN-47603 Compression Gauge Adapter
For equivalent regional tools, refer to Special Tools .
- Ensure that the vehicle's batteries are in good condition, and fully charged.
- Operate the vehicle until the engine is at normal operating temperature.
- Shut off engine.
- Disconnect glow plug nut; remove all 8 glow plugs. All 8 glow plugs must be removed from the engine during each cylinder test to obtain valid test results.
- Prior to taking a compression reading, verify the cranking speed is greater than 140 RPM. If the cranking speed is below 140 RPM, repair the slow cranking speed condition before continuing with the compression test. Refer to «Engine Cranks Slowly»(/chevrolet/express-g2500/2013-2013/remont/charging-system/#battery-charging-system-and-starting-system) .
- Install the EN-47603 adapter in the glow plug hole for the cylinder that is being checked.
- Connect the J 26999 gauge to the EN-47603 adapter.
- Using a remote start switch, crank the engine for 6 compression strokes, puffs, for the cylinder being tested.
- Observe the J 26999 gauge and note the reading as the compression test is being performed. A normal cylinder reading will be indicated if compression builds up quickly and evenly to the specified level. An abnormal reading will be indicated if compression is low on the first compression stroke, starts increasing on the following compression strokes but does not reach the specified level.
- Record the compression reading for the cylinder just tested.
- Disconnect the J 26999 gauge from the EN-47603 adapter and remove adapter from the glow plug hole.
- Repeat steps 8 through 13 for all remaining cylinders. All 8 cylinders must be tested to obtain valid test results. Record the readings.
- The minimum compression in any one cylinder is 2069 kPa (300 psi). There should not be more than 345 kPa (50 psi) difference between a suspect cylinder and the average compression of all 8 cylinders. NOTE: Cylinder to cylinder variation may be at the high end of the specification on engines with less than 20,000 km (12,427 miles). Normal-Compression builds up quickly and evenly to the specified compression for each cylinder. Piston Rings Leaking-Compression is low on the first stroke. Compression builds up with the following strokes but does not reach normal. Valves Leaking-Compression is low on the first stroke. Compression usually does not build up on the following strokes.
Cylinder Leakage Test
Special Tools
- J 35667-A Cylinder Head Leakdown Tester
- J-35667-8 Cylinder Head Leakdown Adapter
For equivalent regional tools, refer to Special Tools .
- Disconnect the battery ground negative cable.
- Remove the glow plugs.
- Rotate the crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke.
- Install J-35667-8 adapter and J 35667-A tester.
- Apply shop air pressure to J 35667-A tester and adjust according to the manufacturers instructions.
- Record the cylinder leakage value. Cylinder leakage that exceeds 25 percent is considered excessive and may require component service. In excessive leakage situations, inspect for the following conditions: Air leakage sounds at the intake manifold tube, may indicate a worn, stuck or burnt intake valve, broken valve spring, incorrect valve lash or damaged valve train components. Air leakage sounds at the exhaust system tailpipe may indicate a worn, burnt, or stuck exhaust valve, broken valve spring, incorrect valve lash or damaged valve train components. Air leakage sounds from the crankcase, oil level indicator tube, or oil fill tube may indicate worn piston rings, a damaged piston, a worn or scored cylinder bore, a damaged engine block or a damaged cylinder head. Air bubbles in the cooling system may indicate a damaged cylinder head or gasket.
- Perform the leakage test on the remaining cylinders and record the values.
Diagnostic Instructions
- Perform the «Diagnostic System Check - Vehicle»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
- Review «Strategy Based Diagnosis»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
- «Diagnostic Procedure Instructions»(/chevrolet/express-g2500/2013-2013/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
| Engine Oil Level Sensor Signal | 2 | 1 | |
| Engine Oil Level Sensor Ground | 1 | ||
| 1. DIC message Engine Oil Level Low always ON 2. DIC message Engine Oil Level Low always OFF | |||
Typical Scan Tool Data
| Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
| Operating Conditions: Ignition ON Parameter Normal Range: OK | |||
| Engine Oil Level Sensor/Switch Signal | OK | Low | OK |
| Engine Oil Level Sensor/Switch Ground | Low | ||
Engine Oil Level Switch
Circuit/System Description
The engine oil level sensor/switch is normally-closed with proper engine oil level. The switch opens when the engine oil level drops below a calibrated level. The engine control module (ECM) monitors the engine oil level signal circuit when the ignition is ON, and the engine is OFF. With the switch in the closed position, the ECM detects a low voltage on the signal circuit. With the switch in the open position, the ECM detects a high voltage on the signal circuit. When high voltage is detected on the signal circuit, the ECM will send a serial data message to the instrument panel cluster (IPC). The IPC will then display a message on the driver information center (DIC) or illuminate a low engine oil level lamp.
The following information determines the message sent from the ECM to the IPC
- The Low Engine Oil Level message lamp is displayed only after the ECM detects a high voltage on the signal circuit for three consecutive ignition cycles, followed by an ignition OFF event from 15 minutes to greater than 50 minutes, depending on engine oil temperatures.
- The Low Engine Oil Level message is turned OFF when the ECM detects a low voltage on the signal circuit after an ignition OFF event for greater than 90 seconds, followed by an ignition ON event for less than 1 second.
Reference Information
Schematic Reference
- «Engine Mechanical Specifications»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-specifications__engine-mechanical-specifications)
- «Instrument Cluster Schematics»(/chevrolet/express-g2500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
Connector End View Reference
Description and Operation
- «Instrument Cluster Description and Operation»(/chevrolet/express-g2500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
- «Indicator/Warning Message Description and Operation»(/chevrolet/express-g2500/2013-2013/remont/gauges-instrument-panels/#instrument-panel-system-displays-and-gauges)
Electrical Information Reference
- «Circuit Testing»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
- «Connector Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
- «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
- «Wiring Repairs»(/chevrolet/express-g2500/2013-2013/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Verification
- Verify proper engine oil level. Add oil as necessary.
- Ignition ON, observe the scan tool Engine Oil Level parameter. The reading should be OK and change to low when the oil level sensor/switch harness connector is disconnected.
Circuit/System Testing
Note. Verify proper engine oil level before continuing with diagnosis.
- Ignition OFF, disconnect the harness connector at the engine oil level sensor and/or switch.
- Ignition OFF, test for less than 2 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
- Ignition ON, verify the scan tool Engine Oil Level Switch parameter reads Low. If the Engine Oil Level Switch parameter reads OK, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the ECM.
- Ignition ON, install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Engine Oil Level Switch parameter reads OK. If the Engine Oil Level Switch parameter reads Low, test the signal circuit terminal A for an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the engine oil level sensor and/or switch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- «Engine Oil Level Sensor and/or Switch Replacement»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-repair-instructions-on-vehicle)
- «Control Module References»(/chevrolet/express-g2500/2013-2013/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for the ECM replacement, setup, and programming
Oil Consumption Diagnosis
The accepted rate of oil consumption, not due to leaks, is the use of 0.946 liter (1 qt) or less within 379 liters (100 gallons) of fuel used. This rate only applies to vehicles under warranty, maintained in accordance with the appropriate maintenance schedule, driven at legal speeds and within design intent of the vehicle.
Oil economy should not be tested until the vehicle has accumulated at least 8000 km (5000 mi) and the oil has been changed for the first time. During initial engine break-in periods before the first oil change, oil consumption may exceed 1.9 liters (2 qts) or more per 379 liters (100 gallons) of fuel used.
| Checks | Causes |
|---|---|
| Preliminary | The causes of excessive oil consumption may include the following conditions: External oil leaks Refer to Oil Leak Diagnosis . Incorrect oil level or improper reading of the oil level indicator With the vehicle on a level surface, run the engine for a few minutes, allow adequate drain down time (2-3 minutes) and check for the correct engine oil level. Improper oil viscosity Refer to the vehicle owners manual and use the recommended SAE grade and viscosity for the prevailing temperatures. Continuous high speed driving and/or severe usage Crankcase ventilation system restrictions or malfunctioning components Oil residue in the charge air cooler system is normal with a closed PCV system Worn valve guides and/or valve stems Worn or improperly installed valve stem oil seals Piston rings broken, worn, not seated properly Allow adequate time for the rings to seat. Replace worn piston rings as necessary. Piston and rings improperly installed or improperly fit to the cylinder bore |
Oil Consumption Diagnosis
Oil Pressure Diagnosis and Testing
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: Low or no engine oil pressure indicates a potentially serious condition with all of the engine mechanical components. Once the cause of the low or no oil pressure condition has been identified, repair all collateral damage to the engine mechanical components as well as the initial cause of the condition. | |||
| 1 | Check engine oil level. Use only the GM service parts brand and recommended grade of engine oil specified for the vehicle. Is the engine oil level between ADD and FULL on the oil level indicator? | Go to Step 2 | |
| 2 | Operate vehicle until engine reaches normal operating temperature. Refer to Engine Mechanical Specifications . Park vehicle on a level surface. Wait 15 minutes. Check engine oil level. Use only the GM service parts brand and recommended grade of engine oil specified for the vehicle. Is the engine oil level between ADD and FULL on the oil level indicator? | Go to Step 3 | |
| 3 | Operate the engine and measure the engine oil pressure with the vehicle gauge or light. Refer to Engine Mechanical Specifications . Is engine oil pressure within specification? | System OK | Go to Step 4 |
| 4 | Remove the oil pressure sender or engine block oil gallery plug. Install the J-21867-6 adapter and J-21867 pressure gauge. Operate the engine and measure the engine oil pressure with the J-21867 pressure gauge. Refer to Engine Mechanical Specifications . Is engine oil pressure within specification? | System OK | Go to Step 5 |
| 5 | Change the engine oil and filter. Use only the GM service parts brand and recommended grade of engine oil specified for the vehicle. Refer to Owners' Manual. Use only the GM service parts brand and recommended type of engine oil filter specified for the vehicle. Refer to Owners' Manual. Operate the engine and measure the engine oil pressure with the mechanical oil pressure gauge. Refer to Engine Mechanical Specifications . Is engine oil pressure within specification? | System OK | Go to Step 6 |
| 6 | Inspect the engine for mechanical damage. Special interest should be shown to the following areas: Malfunctioning oil bypass valve Oil pump worn or dirty Oil pump-to-engine block bolts loose Oil pump O-ring damaged or missing Oil pump to oil pump pipe and screen assembly gasket missing or damaged Oil pump pipe and screen assembly restrictions or damaged Oil pump driven gear damaged or loose Oil pump drive gear damaged Oil cooler restrictions Oil cooler O-rings damaged or missing Excessive bearing clearances Cracked, porous or restricted oil galleries Oil gallery plugs missing or incorrectly installed Damaged or missing oil spray cooling nozzles Inspect the engine for customer modifications. Is there mechanical damage, or customer modifications to the engine? | Go to Step 7 | Go to Step 1 |
| 7 | Repair or replace all damaged or modified components. Is the repair complete? | Go to Step 1 | |
Oil Pressure Diagnosis and Testing
Oil Leak Diagnosis
| Step | Action | Yes | No |
|---|---|---|---|
| NOTE: You can repair most fluid leaks by first visually locating the leak, repairing or replacing the component, or by resealing the gasket surface. Once the leak is identified, determine the cause of the leak. Repair the cause of the leak as well as the leak itself. | |||
| 1 | Operate the vehicle until it reaches normal operating temperature. Park the vehicle on a level surface, over a large sheet of paper or other clean surface. Wait 15 minutes. Check for drippings. Are drippings present? | Go to Step 2 | System OK |
| 2 | Can you identify the type of fluid and the approximate location of the leak? | Go to Step 7 | Go to Step 3 |
| 3 | Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas. Check for leaks at the following locations: Sealing surfaces Fittings Cracked or damaged components Can you identify the type of fluid and the approximate location of the leak? | Go to Step 7 | Go to Step 4 |
| 4 | Completely clean the entire engine and surrounding components. Apply an aerosol-type powder (baby powder, foot powder, etc.) to the suspected area. Operate the vehicle for several kilometers/miles at normal operating temperature and at varying speeds. Identify the type of fluid, and the approximate location of the leak, from the discolorations in the powder surface. Can you identify the type of fluid and the approximate location of the leak? | Go to Step 7 | Go to Step 5 |
| 5 | Use J 28428-E high-intensity black light kit in order to identify the type of fluid, and the approximate location of the leak. Refer to the manufacturer's instructions when using the tool. Can you identify the type of fluid and the approximate location of the leak? | Go to Step 7 | Go to Step 6 |
| 6 | Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas. Check for leaks at the following locations: Sealing surfaces Fittings Cracked or damaged components Can you identify the type of fluid and the approximate location of the leak? | Go to Step 7 | System OK |
| 7 | Inspect the engine for mechanical damage and repair or replace as necessary. Special attention should be shown to the following areas: Plugged or malfunctioning crankcase ventilation system. Refer to Crankcase Ventilation System Inspection/Diagnosis . Higher than recommended fluid levels Higher than recommended fluid pressures Plugged or malfunctioning fluid filters or pressure bypass valves Improperly tightened or damaged fasteners Cracked or porous components Improper sealants or gaskets where required Improper sealant or gasket installation Damaged or worn gaskets or seals Damaged or worn sealing surfaces Inspect the engine for customer modifications. Is there mechanical damage, or customer modifications to the engine? | Go to Step 8 | System OK |
| 8 | Repair or replace all damaged or modified components. Does the engine still leak oil? | Go to Step 1 | System OK |
| NOTE |
|---|
| You can repair most fluid leaks by first visually locating the leak, repairing or replacing the component, or by resealing the gasket surface. Once the leak is identified, determine the cause of the leak. Repair the cause of the leak as well as the leak itself. |
Oil Leak Diagnosis
Crankcase Ventilation System Inspection/Diagnosis
| Concern | Action |
|---|---|
| NOTE: Oil in the charged air cooler, hoses, turbocharger, or intake manifolds is normal with a closed crankcase ventilation system. The maximum crankcase pressure is 4 kPa or 16 in of water at 3,100 RPM measured at the oil level indicator tube. | |
| Excessive crankcase pressure, possible excessive engine oil leaks | Restriction in CDR valve, separator, or hoses Icing at CDR valve in extreme conditions |
| Odors | Cracked hoses Loose or damaged connections |
| Noise | Cracked hoses Loose or damaged connections |
| Smoke | Cracked hoses Loose or damaged connections |
| Excessive Oil Consumption | Restricted oil drain line Stuck CDR valve |
| NOTE |
|---|
| Oil in the charged air cooler, hoses, turbocharger, or intake manifolds is normal with a closed crankcase ventilation system. |
Crankcase Ventilation System Inspection/Diagnosis
Diagnostic Aids
- A chirping or squeal noise may be intermittent due to moisture on the drive belts or the pulleys. It may be necessary to spray a small amount of water on the drive belts in order to duplicate the customers concern. If spraying water on the drive belt duplicates the symptom, cleaning the belt pulleys may be the probable solution.
- If the noise is intermittent, verify the accessory drive components by varying their loads making sure they are operated to their maximum capacity. An overcharged A/C system, power steering system with a pinched hose or wrong fluid, or a generator failing are suggested items to inspect.
- A chirping, squeal or whine noise may be caused by a loose or improper installation of a body or suspension component. Other items of the vehicle may also cause the noise.
- The drive belts will not cause a whine noise.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2 The noise may not be engine related. This step is to verify that the engine is making the noise. If the engine is not making the noise do not proceed further with this table.
- 3 The noise may be an internal engine noise. Removing the drive belts one at a time and operating the engine for a brief period will verify the noise is related to the drive belt. When removing the drive belt the water pump may not be operating and the engine may overheat. Also DTCs may set when the engine is operating with the drive belts removed.
- 4 Inspect all drive belt pulleys for pilling. Pilling is the small balls or pills or it can be strings in the drive belt grooves from the accumulation of rubber dust.
- 6 Misalignment of the pulleys may be caused from improper mounting of the accessory drive component, incorrect installation of the accessory drive component pulley, or the pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a straight edge in the pulley grooves across 2 or 3 pulleys. If a misaligned pulley is found refer to that accessory drive component for the proper installation procedure for that pulley.
- 10 Inspecting of the fasteners can eliminate the possibility that a wrong bolt, nut, spacer, or washer was installed.
- 12 Inspecting the pulleys for being bent should include inspecting for a dent or other damage to the pulleys that would prevent the drive belt from not seating properly in all of the pulley grooves or on the smooth surface of a pulley when the back side of the belt is used to drive the pulley.
- 14 This test is to verify that the drive belt tensioner operates properly. If the drive belt tensioner is not operating properly, proper belt tension may not be achieved to keep the drive belt from slipping which could cause a squeal noise.
- 15 This test is to verify that the drive belt is not too long, which would prevent the drive belt tensioner from working properly. Also if an incorrect length drive belt was installed, it may not be routed properly and may be turning an accessory drive component in the wrong direction.
- 16 Misalignment of the pulleys may be caused from improper mounting of the accessory drive component, incorrect installation of the accessory drive component pulley, or the pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a straight edge in the pulley grooves across 2 or 3 pulleys. If a misaligned pulley is found refer to that accessory drive component for the proper installation procedure for that pulley.
- 17 This test is to verify that the pulleys are the correct diameter or width. Using a known good vehicle compare the pulley sizes.
- 19 Replacing the drive belt when it is not damaged or there is not excessive pilling will only be a temporary repair.
| Step | Action | Yes | No |
|---|---|---|---|
| CAUTION: Refer to Belt Dressing Caution . DEFINITION: The following items are indications of chirping: A high pitched noise that is heard once per revolution of the drive belt or a pulley. Chirping may occur on cold damp start-ups and will subside once the vehicle reaches normal operating temp. DEFINITION: The following items are indications of drive belt squeal: A loud screeching noise that is caused by a slipping drive belt. This is unusual for a drive belt with multiple ribs. The noise occurs when a heavy load is applied to the drive belt, such as an air conditioning compressor engagement snapping the throttle, or slipping on a seized pulley or a faulty accessory drive component. DEFINITION: The following items are indications of drive belt whine: A high pitched continuous noise. The noise may be caused by an accessory drive component failed bearing. | |||
| 1 | Did you review the drive belt symptom operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Mechanical |
| 2 | Verify that there is a chirping, squeal or whine noise. Does the engine make the chirping squeal or whine noise? | Go to Step 3 | Go to Diagnostic Aids |
| 3 | Remove the drive belt. If the engine has multiple drive belts, remove the belts one at a time and perform the test below each time a belt is removed. Operate the engine for no longer than 30-40 seconds. Repeat this test if necessary by removing the remaining belts. Does the chirping, squeal or whine noise still exist? | Go to Symptoms - Engine Mechanical | Go to Step 4 |
| 4 | If diagnosing a chirping noise, inspect for severe pilling exceeding 1/3 of the belt groove depth. If diagnosing a squeal or whine noise, proceed to step 13. Do the belt grooves have pilling? | Go to Step 5 | Go to Step 6 |
| 5 | Clean the drive belt pulleys with a suitable wire brush. Did you complete the repair? | Go to Step 20 | Go to Step 6 |
| 6 | Inspect for misalignment of the pulleys. Are any of the pulleys misaligned? | Go to Step 7 | Go to Step 8 |
| 7 | Replace or repair any misaligned pulleys. Did you complete the repair? | Go to Step 20 | Go to Step 8 |
| 8 | Inspect for bent or cracked brackets. Did you find any bent or cracked brackets? | Go to Step 9 | Go to Step 10 |
| 9 | Replace any bent or cracked brackets. Did you complete the repair? | Go to Step 20 | Go to Step 10 |
| 10 | Inspect for improper, loose or missing fasteners. Did you find the condition? | Go to Step 11 | Go to Step 12 |
| 11 | CAUTION: Refer to Fastener Caution . Tighten any loose fasteners. Refer to Fastener Tightening Specifications . Replace any improper or missing fasteners. Did you complete the repair? | Go to Step 20 | Go to Step 12 |
| 12 | Inspect for a bent pulley. Did you find the condition? | Go to Step 18 | Go to Step 19 |
| 13 | Inspect for an accessory drive component seized bearing or a faulty accessory drive component. If diagnosing a whine noise and the condition still exist, proceed to Diagnostic Aids. Did you find and correct the condition? | Go to Step 20 | Go to Step 14 |
| 14 | Test the drive belt tensioner for proper operation. Refer to Drive Belt Tensioner Diagnosis . Did you find and correct the condition? | Go to Step 20 | Go to Step 15 |
| 15 | Inspect for the correct drive belt length. Did you find and correct the condition? | Go to Step 20 | Go to Step 16 |
| 16 | Inspect for misalignment of a pulley. Did you find and correct the condition? | Go to Step 20 | Go to Step 17 |
| 17 | Inspect for the correct pulley size. Did you find and correct the condition? | Go to Step 20 | Go to Diagnostic Aids |
| 18 | Replace the bent pulley. Did you complete the repair? | Go to Step 20 | Go to Step 19 |
| 19 | Replace the drive belt. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Did you complete the repair? | Go to Step 20 | Go to Diagnostic Aids |
| 20 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| CAUTION |
|---|
| Refer to Belt Dressing Caution . |
| CAUTION |
|---|
| Refer to Fastener Caution . |
Drive Belt Chirping, Squeal, and Whine Diagnosis
The accessory drive components can have an affect on engine vibration. Vibration from the engine operating may cause a body component or another part of the vehicle to make rumbling noise. Vibration can be caused by, but not limited to the air conditioning (A/C) system over charged, the power steering system restricted or the incorrect fluid, or an extra load on the generator. To help identify an intermittent or an improper condition, vary the loads on the accessory drive components.
The drive belt may have a rumbling condition that can not be seen or felt. Sometimes replacing the drive belt may be the only repair for the symptom.
If replacing the drive belt, completing the diagnostic table, and the noise is only heard when the drive belts are installed, there might be an accessory drive component with a failure. Varying the load on the different accessory drive components may aid in identifying which component is causing the rumbling noise.
The numbers below refer to the step numbers on the diagnostic table.
- 2 This test is to verify that the symptom is present during diagnosing. Other vehicle components may cause a similar symptom.
- 3 This test is to verify that one of the drive belts is causing the rumbling noise or vibration. Rumbling noise may be confused with an internal engine noise due to the similarity in the description. Remove only one drive belt at a time if the vehicle has multiple drive belts. When removing the drive belts the water pump may not be operating and the engine may overheat. Also DTCs may set when the engine is operating with the drive belts removed.
- 4 Inspecting the drive belts is to ensure that they are not causing the noise. Small cracks across the ribs of the drive belt will not cause the noise. Belt separation is identified by the plys of the belt separating and may be seen at the edge of the belt our felt as a lump in the belt.
- 5 Small amounts of pilling is normal condition and acceptable. When the pilling is severe the drive belt does not have a smooth surface for proper operation.
- 9 Inspecting of the fasteners can eliminate the possibility that the wrong bolt, nut, spacer, or washer was installed.
- 11 This step should only be performed if the water pump is driven by the drive belt. Inspect the water pump shaft for being bent. Also inspect the water pump bearings for smooth operation and excessive play. Compare the water pump with a known good water pump.
- 12 Accessory drive component brackets that are bent, cracked, or loose may put extra strain on that accessory component causing it to vibrate.
| Step | Action | Yes | No |
|---|---|---|---|
| CAUTION: Refer to Belt Dressing Caution . DEFINITION: The following items are indications of drive belt rumbling: A low pitch tapping, knocking, or thumping noise heard at or just above idle. Heard once per revolution of the drive belt or a pulley. Rumbling may be caused from: Pilling, the accumulation of rubber dust that forms small balls (pills) or strings in the drive belt pulley groove The separation of the drive belt A damaged drive belt DEFINITION: The following items are indications of drive belt vibration: The vibration is engine-speed related. The vibration may be sensitive to accessory load. | |||
| 1 | Did you review the drive belt symptom operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Mechanical |
| 2 | Verify that there is a rumbling noise or that the vibration is engine related. Does the engine make the rumbling noise or vibration? | Go to Step 3 | Go to Diagnostic Aids |
| 3 | NOTE: If the engine has multiple drive belts, remove the belts one at a time and perform the test below each time a belt is removed. Remove the drive belt. Operate the engine for no longer than 30-40 seconds. Repeat this test if necessary by removing the remaining belt(s). Does the rumbling or vibration still exist? | Go to Symptoms - Engine Mechanical or Go to Vibration Analysis - Engine | Go to Step 4 |
| 4 | Inspect the drive belts for wear, damage, separation, sections of missing ribs, and debris build-up. Did you find any of these conditions? | Go to Step 7 | Go to Step 5 |
| 5 | Inspect for severe pilling of more than 1/3 of the drive belt pulley grooves. Did you find severe pilling? | Go to Step 6 | Go to Step 7 |
| 6 | Clean the drive belt pulleys using a suitable wire brush. Reinstall the drive belts. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Did you correct the condition? | Go to Step 8 | Go to Step 7 |
| 7 | Install a new drive belt. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Did you complete the replacement? | Go to Step 8 | Go to Step 9 |
| 8 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 9 |
| 9 | Inspect for improper, loose or missing fasteners. Did you find any of these conditions? | Go to Step 10 | Go to Step 11 |
| 10 | CAUTION: Refer to Fastener Caution . Tighten any loose fasteners. Refer to Fastener Tightening Specifications . Replace improper or missing fasteners. Did you complete the repair? | Go to Step 13 | Go to Step 11 |
| 11 | Inspect for a bent water pump shaft. Refer to Water Pump Replacement (Diesel) . Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
| 12 | Inspect for bent or cracked brackets. Did you find and correct the condition? | Go to Step 13 | Go to Diagnostic Aids |
| 13 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
| CAUTION |
|---|
| Refer to Belt Dressing Caution . |
| NOTE |
|---|
| If the engine has multiple drive belts, remove the belts one at a time and perform the test below each time a belt is removed. |
| CAUTION |
|---|
| Refer to Fastener Caution . |
Drive Belt Rumbling and Vibration Diagnosis
If the drive belt repeatedly falls off the drive belt pulleys, this is because of pulley misalignment.
An extra load that is quickly applied on released by an accessory drive component may cause the drive belt to fall off the pulleys. Verify the accessory drive components operate properly.
If the drive belt is the incorrect length, the drive belt tensioner may not keep the proper tension on the drive belt.
Excessive wear on a drive belt is usually caused by an incorrect installation or the wrong drive belt for the application.
Minor misalignment of the drive belt pulleys will not cause excessive wear, but will probably cause the drive belt to make a noise or to fall off.
Excessive misalignment of the drive belt pulleys will cause excessive wear but may also make the drive belt fall off.
The numbers below refer to the step numbers on the diagnostic table.
- 2 This inspection is to verify the condition of the drive belt. Damage may of occurred to the drive belt when the drive belt fell off. The drive belt may of been damaged, which caused the drive belt to fall off. Inspect the belt for cuts, tears, sections of ribs missing, or damaged belt plys.
- 4 Misalignment of the pulleys may be caused from improper mounting of the accessory drive component, incorrect installation of the accessory drive component pulley, or the pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a straight edge in the pulley grooves across two or three pulleys. If a misaligned pulley is found refer to that accessory drive component for the proper installation procedure of that pulley.
- 5 Inspecting the pulleys for being bent should include inspecting for a dent or other damage to the pulleys that would prevent the drive belt from not seating properly in all of the pulley grooves or on the smooth surface of a pulley when the back side of the belt is used to drive the pulley.
- 6 Accessory drive component brackets that are bent or cracked will let the drive belt fall off.
- 7 Inspection of the fasteners can eliminate the possibility that a wrong bolt, nut , spacer, or washer was installed. Missing, loose, or the wrong fasteners may cause pulley misalignment from the bracket moving under load. Over tightening of the fasteners may cause misalignment of the accessory component bracket.
- 13 The inspection is to verify the drive belt is correctly installed on all of the drive belt pulleys. Wear on the drive belt may be caused by mis-positioning the drive belt by one groove on a pulley.
- 14 The installation of a drive belt that is too wide or too narrow will cause wear on the drive belt. The drive belt ribs should match all of the grooves on all of the pulleys.
- 15 This inspection is to verify the drive belt is not contacting any parts of the engine or body while the engine is operating. There should be sufficient clearance when the drive belt accessory drive components load varies. The drive belt should not come in contact with an engine or a body component when snapping the throttle.
| Step | Action | Yes | No |
|---|---|---|---|
| CAUTION: Refer to Belt Dressing Caution . DEFINITION: The drive belt falls off the pulleys or may not ride correctly on the pulleys.DEFINITION: Wear at the outside ribs of the drive belt due to an incorrectly installed drive belt. | |||
| 1 | Did you review the Drive Belt Symptom operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Mechanical |
| 2 | If diagnosing excessive wear, proceed to step 13. If diagnosing a drive belt that falls off, inspect for a damaged drive belt. Did you find the condition? | Go to Step 3 | Go to Step 4 |
| 3 | Install a new drive belt. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Does the drive belt continue to fall off? | Go to Step 4 | System OK |
| 4 | Inspect for misalignment of the pulleys. Did you find and repair the condition? | Go to Step 12 | Go to Step 5 |
| 5 | Inspect for a bent or dented pulley. Did you find and repair the condition? | Go to Step 12 | Go to Step 6 |
| 6 | Inspect for a bent or a cracked bracket. Did you find and repair the condition? | Go to Step 12 | Go to Step 7 |
| 7 | Inspect for improper, loose or missing fasteners. Did you find loose or missing fasteners? | Go to Step 8 | Go to Step 9 |
| 8 | CAUTION: Refer to Fastener Caution . Tighten any loose fasteners. Refer to Fastener Tightening Specifications . Replace improper or missing fasteners. Does the drive belt continue to fall off? | Go to Step 9 | System OK |
| 9 | Test the drive belt tensioner for operating correctly. Refer to Drive Belt Tensioner Diagnosis . Does the drive belt tensioner operate correctly? | Go to Step 11 | Go to Step 10 |
| 10 | Replace the drive belt tensioner. Refer to Drive Belt Tensioner Replacement - Accessory . Does the drive belt continue to fall off? | Go to Step 11 | System OK |
| 11 | Inspect for failed drive belt idler and drive belt tensioner pulley bearings. Did you find and repair the condition? | Go to Step 12 | Go to Diagnostic Aids |
| 12 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 13 |
| 13 | Inspect the drive belt for the proper installation. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Did you find this condition? | Go to Step 16 | Go to Step 14 |
| 14 | Inspect for the proper drive belt. Did you find this condition? | Go to Step 16 | Go to Step 15 |
| 15 | Inspect for the drive belt rubbing against a bracket, hose, or wiring harness. Did you find and repair the condition? | Go to Step 17 | Go to Diagnostic Aids |
| 16 | Replace the drive belt. Refer to Drive Belt Replacement - Accessory , or Air Conditioning Compressor Belt Replacement . Did you complete the replacement? | Go to Step 17 | |
| 17 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | |
| CAUTION |
|---|
| Refer to Belt Dressing Caution . |
| CAUTION |
|---|
| Refer to Fastener Caution . |
Drive Belt Falls Off and Excessive Wear Diagnosis
Drive Belt Tensioner Diagnosis
- Remove the drive belt. Refer to «Drive Belt Replacement»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-repair-instructions-on-vehicle) .
- Position a 3/8-inch drive breaker bar into the drive belt tensioner opening and rotate the tensioner counterclockwise.
- Move the drive belt tensioner through its full travel. The movement should feel smooth There should be no binding The tensioner should return freely
- If any binding is observed, replace the drive belt tensioner. Refer to «Drive Belt Tensioner Replacement»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-repair-instructions-on-vehicle) .
- Install the drive belt. Refer to «Drive Belt Replacement»(/chevrolet/express-g2500/2013-2013/remont/mechanical/#engine-mechanical-66l-lgh-repair-instructions-on-vehicle) .
See also:
• Diagnostic Starting Point - Vehicle
• Disassembled Views
• Engine Component Description
• Drive Belt System Description
• Strategy Based Diagnosis
• Special Tools
• Loss of Coolant
• Cylinder Head Cleaning and Inspection
• Cylinder Head Replacement - Left Side
• Cylinder Head Replacement - Right Side
• Fuel Leak Diagnosis
• Engine Cranks Slowly
• Battery Disconnect Warning
• Diagnostic System Check - Vehicle
• Diagnostic Procedure Instructions
• Engine Mechanical Specifications
• Instrument Cluster Schematics
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Engine Oil Level Sensor and/or Switch Replacement
• Belt Dressing Caution
• Symptoms - Engine Mechanical
• Fastener Caution
• Fastener Tightening Specifications
• Drive Belt Tensioner Diagnosis
• Drive Belt Replacement - Accessory
• Vibration Analysis - Engine
• Water Pump Replacement (Diesel)
• Base Engine Misfire without Internal Engine Noises
• Base Engine Misfire with Abnormal Internal Lower Engine Noises
• Base Engine Misfire with Abnormal Valve Train Noise
• Base Engine Misfire with Coolant Consumption
• Base Engine Misfire with Excessive Oil Consumption
• Engine Compression Test
• Engine Noise on Start-Up, but Only Lasting a Few Seconds
• Upper Engine Noise, Regardless of Engine Speed
• Lower Engine Noise, Regardless of Engine Speed
• Engine Noise Under Load
• Engine Will Not Crank - Crankshaft Will Not Rotate
• Oil Pressure Diagnosis and Testing
• Oil Leak Diagnosis
• Drive Belt Rumbling and Vibration Diagnosis
• Drive Belt Tensioner Diagnosis
• Fuel in Engine Oil
• Crankcase Ventilation System Inspection/Diagnosis