Diagnostic Starting Point - Engine Mechanical
Begin the system diagnosis by reviewing the Disassembled Views , Engine Component Description , and Lubrication Description in Engine Mechanical - 6.6L Unit Repair Manual, and the . Reviewing the description and operation information will help you determine the correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and operation information will also help you determine if the condition described to you by the customer is normal operation. Refer to Symptoms - Engine Mechanical in order to identify the correct procedure for diagnosing the system and where the procedure is located.
Strategy Based Diagnostics
- Perform the Diagnostic System Check in Engine Controls before using the symptom tables, if applicable.
- Review the system operations in order to familiarize yourself with the system functions. Refer to «Disassembled Views»(ref-238285-S30428414032006072400000) , «Engine Component Description»(ref-238285-S29311583342006072400000) , and «Lubrication Description»(ref-238285-S00283048812006072400000) .
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 in General Information.
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.
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»(ref-238285-S28697844592006072400000)
- «Base Engine Misfire with Abnormal Internal Lower Engine Noises»(ref-238285-S13927314552006072400000)
- «Base Engine Misfire with Abnormal Valve Train Noise»(ref-238285-S10562858322006072400000)
- «Base Engine Misfire with Coolant Consumption»(ref-238285-S32632329212006072400000)
- «Base Engine Misfire with Excessive Oil Consumption»(ref-238285-S41365432642006072400000)
- «Engine Compression Test»(ref-238285-S29245004382006072400000)
- «Engine Noise on Start-Up, but Only Lasting a Few Seconds»(ref-238285-S06250973922006072400000)
- «Upper Engine Noise, Regardless of Engine Speed»(ref-238285-S34936884882006072400000)
- «Lower Engine Noise, Regardless of Engine Speed»(ref-238285-S42500724192006072400000)
- «Engine Noise Under Load»(ref-238285-S07133287822006072400000)
- «Engine Will Not Crank - Crankshaft Will Not Rotate»(ref-238285-S01550848462006072400000)
- «Oil Pressure Diagnosis and Testing»(ref-238285-S36628170612006072400000)
- «Oil Leak Diagnosis»(ref-238285-S41509219672006072400000)
- «Drive Belt Chirping Diagnosis»(ref-238285-S19209102232006072400000)
- «Drive Belt Squeal Diagnosis»(ref-238285-S32634146212006072400000)
- «Drive Belt Whine Diagnosis»(ref-238285-S03886090952006072400000)
- «Drive Belt Rumbling Diagnosis»(ref-238285-S41326396352006072400000)
- «Drive Belt Vibration Diagnosis»(ref-238285-S32119915202006072400000)
- «Drive Belt Falls Off Diagnosis»(ref-238285-S07351357802006072400000)
- «Drive Belt Excessive Wear Diagnosis»(ref-238285-S29911991982006072400000)
- «Drive Belt Tensioner Diagnosis»(ref-238285-S26116007872006072400000)
Engine Compression Test
Tools Required
- J 26999 Compression Gage. See «Special Tools»(ref-238285-S38807441172006072400000) .
- EN-47603 Compression Gage Adapter. See «Special Tools»(ref-238285-S38807441172006072400000) .
- J 43244 Relay Puller Pliers
- 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.
- Disable fuel delivery system, by removing the IGN 1 relay with J 43244 .
- 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»(ref-238228-S20970594432006072400000) in Engine Electrical.
- Install the EN-47603 in the glow plug hole for the cylinder that is being checked. See «Special Tools»(ref-238285-S38807441172006072400000) .
- Connect the J 26999 to the EN-47603 . See «Special Tools»(ref-238285-S38807441172006072400000) .
- Using the vehicle's starter motor, rotate or crank the engine for 6 compression strokes, puffs, for the cylinder being tested.
- Observe the J 26999 and note the reading as the compression test is being performed. See «Special Tools»(ref-238285-S38807441172006072400000) . 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 from the EN-47603 and remove adapter from the glow plug hole. See «Special Tools»(ref-238285-S38807441172006072400000) .
- 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. 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
Tools Required
- J 35667-A Cylinder Head Leakdown Tester
- J-35667-8 Cylinder Head Leakdown Adapter. See «Special Tools»(ref-238285-S38807441172006072400000) .
Scheme 451
- 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 and J 35667-A . See «Special Tools»(ref-238285-S38807441172006072400000) .
- Apply shop air pressure to J 35667-A 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.
Oil Consumption Diagnosis
The accepted rate of oil consumption, not due to leaks, is the use of more than 0.946 liter (1 qt) 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 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 gage 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 a mechanical oil pressure gage. Operate the engine and measure the engine oil pressure with the mechanical oil pressure gage. 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 gage. 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 |
|---|---|---|---|
| IMPORTANT: 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 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 |
| IMPORTANT |
|---|
| 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 |
|---|---|
| IMPORTANT: 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. | |
| PVC check valve stuck closed | Excessive crankcase pressure Possible oil leaks. Replace the valve. |
| Odors | Normal situation |
| Noise | Cracked hoses |
| Smoke | Damaged PCV diaphragm |
| Excessive Oil Consumption | Damaged PCV diaphragm, missing or broken spring |
| IMPORTANT |
|---|
| 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
If a chirping noise occurs during engine shutdown, this is considered normal and is due to the engine's high compression. The chirping noise may be intermittent due to moisture on the drive belt or the accessory drive pulleys. In order to duplicate the customer's concern, it may be necessary to spray a small amount of water onto the drive belt. If spraying water onto the drive belt duplicates the symptom, cleaning the accessory belt pulleys may be the most probable solution.
A loose or improper installation of a body or suspension component, or other items on the vehicle may also cause the chirping noise.
If a chirping noise occurs during engine shutdown, this is considered normal and is due to the engine's high compression.
A loose or improper installation of a body or suspension component, or other items on the vehicle may cause the squeal noise.
If the squeal is intermittent, verify that it is not the accessory drive components by varying their loads, making sure they are operating to their maximum capacity. An overcharged air conditioning (A/C) system, a power steering system restriction or the incorrect fluid, or a failing generator are suggested items to inspect.
The drive belt will not cause the whine.
If the whine is intermittent, verify that it is not the accessory drive components by varying their loads, making sure they are operating to their maximum capacity. An overcharged air conditioning (A/C) system, a power steering system restriction or the incorrect fluid, or a failing generator are suggested items to inspect.
Vibration from the engine operating may cause a body component or another part of the vehicle to make rumbling noise.
The drive belt may have a condition that can not be seen or felt. Sometimes replacing the drive belt may be the only repair for the symptom.
If, after replacing the drive belt and completing the diagnostic table, the rumbling is only heard with the drive belt installed, there might be an accessory drive component failure. Varying the load on the accessory drive components may aid in identifying which component is causing the rumbling noise.
The accessory drive components can have an affect on engine vibration. An overcharged air conditioning (A/C) system, a power steering system restriction, or the incorrect fluid, or an extra load placed on the generator are suggested items to inspect. To help identify an intermittent or an improper condition, vary the loads on the accessory drive components.
If the drive belt repeatedly falls off the accessory drive belt pulleys, this may be caused by a pulley misalignment.
An extra load that is quickly applied or released by an accessory drive component may cause the drive belt to fall off. Verify that the accessory drive components are operating properly.
If the drive belt is the incorrect length, the drive belt tensioner may not maintain the proper tension on the drive belt.
Excessive wear on a drive belt is usually caused by incorrect installation or the incorrect drive belt for the application.
Minor misalignment of the accessory drive belt pulleys will not cause excessive wear, but will probably cause the drive belt to make a noise or fall off.
Excessive misalignment of the accessory drive belt pulleys will cause excessive wear and may also make the drive belt fall off.