Engine Mechanical - 4.2L: Diagnosis Chevrolet TrailBlazer I

Diagnostic Starting Point - Engine Mechanical

Begin the system diagnosis by reviewing the DISASSEMBLED VIEWS , Engine Component Description , and Lubrication Description . 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 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

1. Perform A Diagnostic System Check in Engine Controls before using the symptom tables (if applicable).
2. Review the system operations in order to familiarize yourself with the system functions. Refer to «DISASSEMBLED VIEWS»(ref-188499-S25078937442005090700000) , «Engine Component Description»(ref-188499-S28697755442005090700000) , and «Lubrication Description»(ref-188499-S14808546742005090700000) .

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.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the engine.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Check for the correct oil level, proper oil viscosity, and correct filter application.
4. 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.
5. 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

1. «BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES»(ref-188499-S00889839102005090700000)
2. «BASE ENGINE MISFIRE WITH ABNORMAL INTERNAL LOWER ENGINE NOISES»(ref-188499-S23273362372005090700000)
3. «BASE ENGINE MISFIRE WITH ABNORMAL VALVE TRAIN NOISE»(ref-188499-S28149788652005090700000)
4. «BASE ENGINE MISFIRE WITH COOLANT CONSUMPTION»(ref-188499-S11032510712005090700000)
5. «BASE ENGINE MISFIRE WITH EXCESSIVE OIL CONSUMPTION»(ref-188499-S38719316802005090700000)
6. «ENGINE COMPRESSION TEST»(ref-188499-S17991184832005090700000)
7. «ENGINE NOISE ON START-UP, BUT ONLY LASTING A FEW SECONDS»(ref-188499-S18592797442005090700000)
8. «UPPER ENGINE NOISE, REGARDLESS OF ENGINE SPEED»(ref-188499-S13321029432005090700000)
9. «LOWER ENGINE NOISE, REGARDLESS OF ENGINE SPEED»(ref-188499-S30182249942005090700000)
10. «ENGINE NOISE UNDER LOAD»(ref-188499-S11476118032005090700000)
11. «ENGINE WILL NOT CRANK - CRANKSHAFT WILL NOT ROTATE»(ref-188499-S30057737492005090700000)
12. «OIL CONSUMPTION DIAGNOSIS»(ref-188499-S23072289642005090700000)
13. «OIL PRESSURE DIAGNOSIS AND TESTING»(ref-188499-S23284521912005090700000)
14. «OIL LEAK DIAGNOSIS»(ref-188499-S13290222322005090700000)

Scheme 824

Scheme 825

Scheme 826

Scheme 827

Scheme 828

Scheme 829

Scheme 830

Scheme 831

Scheme 832

Scheme 833

Scheme 834

Scheme 835

Scheme 836

Scheme 837

Engine Compression Test

Tools Required

J 38722 Compression Tester

A compression pressure test of the engine cylinders determines the condition of the rings, the valves, and the head gasket.

Scheme 838

1. Remove the air duct from the throttle control module.
2. Remove the ignition control modules.
3. Disable the fuel system.
4. Remove the spark plugs.
5. Measure the engine compression, using the following procedure: 5.1. Firmly install J 38722 to the spark plug hole. 5.2. Have an assistant crank the engine through at least four compression strokes in the testing cylinder. 5.3. Check and record the readings on J 38722 at each stroke. 5.4. Disconnect J 38722 . 5.5. Repeat the compression test for each cylinder.
6. Record the compression readings from all of the cylinders. A normal reading should be approximately 1482 kPa (215 psi). The lowest reading should not be less than 70 percent of the highest reading.
7. The following are examples of the possible measurements: When the compression measurement is normal, the compression builds up quickly and evenly to the specified compression on each cylinder. When the compression is low on the first stroke and tends to build up on the following strokes, but does not reach the normal compression, or if the compression improves considerably with the addition of three squirts of oil, the piston rings may be the cause. When the compression is low on the first stroke and does not build up in the following strokes, or the addition of oil does not affect the compression, the valves may be the cause. When the compression is low on two adjacent cylinders, or coolant is present in the crankcase, the head gasket may be the cause.
8. Install the air duct to the throttle body.
9. Install the spark plugs.
10. Enable the fuel system.
11. Install the ignition control modules.

Cylinder Leakage Test

Tools Required

J 35667-A Cylinder Head Leakdown Tester

Scheme 839

1. Disconnect the battery ground negative cable.
2. Remove the spark plugs. Refer to «SPARK PLUGS»(ref-159085-S02952502512003111400000) .
3. Rotate the crankshaft to place the piston in the cylinder being tested at Top Dead Center (TDC) of the compression stroke.
4. Install J 35667-A . IMPORTANT: It may be necessary to hold the crankshaft balancer bolt to prevent the engine from rotating.
5. Apply shop air pressure to J 35667-A and adjust according to the manufacturers instructions.
6. 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 throttle control module or air inlet hose may indicate a worn or burnt intake valve or a broken valve spring. Air leakage sounds at the exhaust system tailpipe may indicate a worn or burnt exhaust valve or a broken valve spring. 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 a damaged cylinder head gasket.
7. Perform the leakage test on the remaining cylinders and record the values.

Scheme 840

Oil Pressure Diagnosis and Testing

Tools Required

Scheme 841

1. J 21867 Pressure Gage and Hose Assembly
2. J 42907 Oil Pressure Tester

1. With the vehicle on a level surface, run the vehicle for a few minutes, allow adequate drain down time (2-3 minutes) and measure for a low oil level.
2. If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.
3. Run the engine briefly (10-15 seconds) and verify low or no oil pressure on the vehicle gage or light.
4. Listen for a noisy valve train or a knocking noise.
5. Inspect for the following: Oil diluted by water or glycol (anti freeze) Foamy oil
6. Remove the oil filter and install the J 42907 .
7. Install J 21867 or equivalent to the J 42907 .
8. Run the engine and measure the engine oil pressure.
9. Compare the readings to «ENGINE MECHANICAL SPECIFICATIONS»(ref-188499-S18523790822005090700000) .
10. If the engine oil pressure is below specifications, inspect the engine for one or more of the following: Oil pump worn or dirty Refer to «Oil Pump Cleaning and Inspection»(ref-188499-S26519684682005090700000) . Oil pump screen loose, plugged, or damaged Oil pump screen O-ring seal missing or damaged Malfunctioning oil pump pressure regulator valve Excessive bearing clearance Cracked, porous, or restricted oil galleries Oil gallery plugs missing or incorrectly installed Refer to «Engine Block Plug Installation»(ref-188499-S38263637282005090700000) . Broken valve lash adjusters Repair as necessary
11. If the reading on J 21867 or equivalent is within specifications, inspect for the following: Plugged or incorrect oil filter and/or malfunctioning oil bypass valve Malfunctioning vehicle oil pressure gage or sensor Repair as necessary

Scheme 842

Scheme 843

Diagnostic Aids

The symptom may be intermittent due to moisture on the drive belt(s) or the pulleys. It may be necessary to spray a small amount of water on the drive belt(s) in order to duplicate the customers concern. If spraying water on the drive belt(s) duplicates the symptom, cleaning the belt pulleys may be the probable solution.

A loose or improper installation of a body component, a suspension component, or other items of the vehicle may cause the chirping noise.

A loose or improper installation of a body component, a suspension component, or other items of the vehicle may cause the squeal noise.

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.

The drive belt(s) will not cause the whine noise. If the whine noise is intermittent, verify the accessory drive components by varying their loads making sure they are operated to their maximum capacity. Such items but not limited to may be an A/C system overcharged, the power steering system restricted or the wrong fluid, or the generator failing.

Vibration from the engine operating may cause a body component or another part of the vehicle to make rumbling noise.

The drive belt(s) 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 replacing the drive belt(s), completing the diagnostic table, and the noise is only heard when the drive belt(s) is 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 accessory drive components can have an affect on engine vibration. Such as but not limited to the 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.

If the drive belt(s) 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(s) is the incorrect length, the drive belt tensioner may not keep the proper tension on the drive belt.

Excessive wear on a drive belt(s) 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(s) 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(s) fall off.

Inspection Procedure

Note. Allowing the drive belt tensioner to snap into the free position may result in damage to the tensioner.

1. Remove the drive belts. Refer to «DRIVE BELT REPLACEMENT»(ref-188499-S12793626322005090700000) .
2. Position a hex-head socket on the belt tensioner pulley bolt head.
3. Move the drive belt tensioner through it's full travel. The movement should feel smooth. There should be no binding. The tensioner should return freely.
4. If any binding is observed, replace the tensioner. Refer to «DRIVE BELT TENSIONER REPLACEMENT»(ref-188499-S22393493052005090700000) .
5. Install the drive belt. Refer to «DRIVE BELT REPLACEMENT»(ref-188499-S12793626322005090700000) .

Camshaft Position (CMP) Actuator Diagnosis

The camshaft position actuator will only phase 25-cam degrees retard (counterclockwise). Full advance (clockwise) is 0 degrees. The arrow on the actuator shows advance direction.

Scheme 844

The camshaft position actuator should always be serviced/replaced in the full advanced position (full clockwise or 0 degrees). New replacement (service) camshaft position actuators are shipped at full advance or 0 degrees. To be sure the camshaft position actuator is performing properly, perform the following to help in the diagnostics.

Scheme 845

Scheme 846

Scheme 847

1. Use a 25 mm (1 in) wrench on the hex of the exhaust camshaft to rotate the exhaust camshaft and camshaft position actuator back and forth (clockwise and counterclockwise) to purge the oil out of the camshaft position actuator.
2. To perform an on-vehicle test, scribe or draw a line (1) on the camshaft position actuator, flush with the head, in the full advanced position. See arrow on the camshaft position actuator. With the engine at TDC on #1 cylinder, the wording should be level.
3. Use a 25 mm (1 in) wrench on the hex of the exhaust camshaft to rotate the camshaft and camshaft position actuator counterclockwise to full retard.
4. Scribe or draw a line (2) on the camshaft position actuator at that position.
5. Measure the distance between the two lines. The measurement (3) should be 14-15 mm (0.55-0.59 in). If the measurement is far more or far less, the camshaft position actuator needs to be replaced.

Scheme 848

1. Install 3/8 inch breaker bar on the drivebelt tensioner arm and turn the breaker bar clockwise enough to relieve the tension on the drivebelt.
2. Remove the drivebelt.
3. Release the tension on the tensioner arm.

Engine Block Cleaning and Inspection

Tools Required

1. J 8001 Dial Indicator Set
2. J 8087 Cylinder Bore Gauge
3. J 36660-A Torque/Angle Meter

Scheme 849

Scheme 850

Scheme 851

Scheme 852

1. Clean the sealing material from all gasket mating surfaces.
2. Clean the engine block with a cleaning solution.
3. Flush the engine block with clean water.
4. Clean the oil passages.
5. Coat the cylinder bores and the machined surfaces with engine oil.
6. Inspect the threaded holes. Clean the holes with a tap, if needed.
7. Use a straight edge and a feeler gauge to check the deck surface for flatness. Carefully remove any minor irregularities. Replace the block if there is more than 0.08 mm (0.003 in) gap.
8. Replace the engine block if the bores are out of specification.
9. Inspect the cylinder bores. Use J 8087 to measure the cylinder bore. Inspect the bores for the following conditions: Wear Taper Runout Ridging IMPORTANT: If the bore is worn beyond the limits, bore the cylinders and refit with the one oversized piston available.
10. Leave sufficient material to allow finish honing when fitting the pistons.
11. Inspect the oil pan rail for nicks. Use a flat file to remove an nicks.
12. Inspect the front cover attaching area for nicks. Use a flat file to remove any nicks.
13. Inspect the mating surfaces of the transmission case.
14. Use the following procedure to measure the engine block flange runout at the mounting bolt hole bosses: 14.1. Temporarily install the crankshaft. Measure the crankshaft flange runout. 14.2. Hold a gauge plate flat against the crankshaft flange. 14.3. Place J 8001 (dial indicator stem) on the transmission mounting bolt hole boss. Set the indicator to zero 14.4. Record the readings obtained from all of the bolt hole bosses. The measurements should not vary more than 0.25 mm (0.010 in). 14.5. Recheck the crankshaft flange runout if the readings vary more than 0.25 mm (0.010 in). If the crankshaft flange runout is within the specification, replace the engine block.
15. Remove the crankshaft. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
16. Re-install the crankshaft bearing caps, stiffener, and bolts. Tighten 16.1. Tighten the crankshaft bearing cap bolts to 25 N.m (18 lb ft). 16.2. Use J 36660-A to tighten the crankshaft bearing cap bolts an additional 180 degrees. IMPORTANT: Perform the following inspections, and reconditioning (if necessary), with the crankshaft main bearing caps installed and tightened to specification.
17. Inspect the crankshaft main bearing bores. Use J 8087 to measure the bearing bore concentricity and alignment.
18. Remove the crankshaft main bearing cap stiffener and main bearing caps with bearings.

Crankshaft and Bearings Cleaning and Inspection

Tools Required

1. J 36660-A Torque Angle Meter
2. J 8087 Cylinder Bore Gauge

Scheme 853

Scheme 854

Scheme 855

Scheme 856

1. Clean the crankshaft of all elements.
2. Inspect the crankshaft oil passages for obstructions.
3. Inspect the crankshaft for the following conditions: Damaged threads (1) Damaged mounting faces Worn crankshaft pin (2) Wear without any grooves or scratches (3) Grooves or scoring (3) Scratches (3) Pitting or embedded bearing material (3) Overheating (discoloration) (3)
4. Inspect the corresponding crankshaft bearing inserts for embedded material and determine the source of the material. IMPORTANT: If cracks, severe gouges or burned spots are found, replace the crankshaft. Remove slight roughness using a fine polishing cloth soaked in clean engine oil. Remove any burrs using a fine oil stone.
5. Inspect the outer surfaces of the crankshaft bearings for the following conditions: Wear - surface wear indicates either movement of the insert or high spots in the surrounding material (spot wear) Overheating or discoloration Looseness or rotation indicated by flattened tangs and wear grooves IMPORTANT: Note the location of the crankshaft main bearing high spots. If the spots are not in line, the crankshaft is bent. Replace the crankshaft.
6. Inspect the crankshaft main bearings for craters or pockets. Flattened sections on the crankshaft bearing halves also indicate fatigue.
7. Inspect the thrust surfaces of the main thrust bearing for the following conditions: Wear Grooving - Grooves are caused by irregularities of the crankshaft thrust surface.
8. Inspect the crankshaft bearings for excessive scoring or discoloration.
9. Inspect the crankshaft bearings for dirt or imbedded debris.
10. Inspect the crankshaft bearings for improper seating indicated by bright, polished sections.
11. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal. IMPORTANT: If crankshaft bearing failure is due to conditions other than normal wear, investigate the cause of the condition. Inspect the crankshaft or connecting rod bearing bores.
12. Inspect the connecting rod bearing bores using the following procedure: 12.1. Tighten the connecting rod bearing cap to specification. 12.2. Use J 8087 to measure the bearing bore for taper and out-of-round. Record the readings. 12.3. No taper or out-of-round should exist.
13. Measure the crankshaft bearing journal diameter with a micrometer in several places, 90 degrees apart. Average the measurements.
14. Measure the crankshaft bearing journal taper and runout. IMPORTANT: Refer to the pin stamp on the crankshaft main bearing caps for sequence and direction of installation. The pin stamp arrow points to the front of the engine.
15. Install the crankshaft bearing caps.
16. Install the crankshaft main bearing cap stiffener. NOTE: Refer to «FASTENER NOTICE»(ref-175132-S17785009232005041500000) in Cautions and Notices.
17. Install the crankshaft bearing cap bolts. Tighten 17.1. Tighten the crankshaft bearing cap bolts to 25 N.m (18 lb ft). 17.2. Use J 36660-A to tighten the crankshaft bearing cap bolts an additional 180 degrees.
18. Measure the crankshaft main bearing inside diameter with an inside micrometer.
19. Measure the connecting rod inside diameter in the same direction as the length of the rod with an inside micrometer.
20. If the specified clearances cannot be met, the crankshaft, connecting rods, or block may need to be replaced.

Scheme 857

1. Inspect the crankshaft balancer sealing area for grooves, nicks, or burs (1).
2. Inspect the crankshaft balancer belt ribs for dents or damage (2).
3. Replace the crankshaft balancer if damage is present.

Scheme 858

1. Inspect the engine flywheel for cracks (1).
2. Inspect the engine flywheel teeth for damage (2).
3. Replace the engine flywheel if damage is present.

Piston, Connecting Rod, and Bearings Cleaning and Inspection

Tools Required

J 8087 Cylinder Bore Gauge

Scheme 859

Scheme 860

Scheme 861

Scheme 862

Scheme 863

Scheme 864

Scheme 865

1. Clean and soak the following components in a carburetor cleaning solution to remove carbon, sludge, and varnish: Piston Piston pin Connecting rod
2. Install the connecting rod cap.
3. Place the connecting rod assembly on a checking fixture.
4. Inspect the connecting rod assembly for bending or twisting.
5. Replace any bent or twisted connecting rods.
6. If the connecting rod large bore contains minor scratches or abrasions, clean the bore in a circular direction with light emery paper. DO NOT scrape the connecting rod or cap.
7. Measure the piston pin to connecting rod bore using the following procedure: Using an outside micrometer, take two measurements of the piston pin in the area of the connecting rod contact. Using an inside micrometer, measure the connecting rod piston pin bore. Subtract the piston pin diameter from the piston pin bore diameter. The clearance should not be more than 0.018 mm (0.0007 in).
8. If there is excessive clearance, replace the piston pin.
9. If there is still excessive clearance, replace the connecting rod.
10. If there is evidence of pin bore or pin scoring, replace the rod and pin assembly.
11. Inspect the connecting rod bearings for the following conditions: Craters or pockets Flattened sections Excessive scoring or discoloration. Imbedded debris Bright, polished sections
12. Inspect the inside of the connecting rod bearing and outside diameter of the connecting rod bearing journal for wear. This indicates high spots.
13. Inspect the connecting rod bearing bore for taper and out-of-round.
14. Inspect the connecting rod bolts for stretching (compare to new or known good bolt). (1) is a stretched bolt, (2) is a new or good bolt.
15. Clean the piston skirts and the pins with a cleaning solvent. DO NOT wire brush any part of the piston.
16. Clean the piston ring grooves. Ensure that the oil ring holes and slots are clean.
17. Inspect the pistons for the following conditions: Cracked ring lands, skirts, or pin bosses Ring grooves for nicks, burrs that may cause binding Warped or worn ring lands Eroded areas at the top of the piston Scuffed or damaged skirts Worn piston pin bores
18. Replace pistons that show any signs or damage or excessive wear. IMPORTANT: When fitting pistons, consider both the piston and the cylinder bore conditions together. Production and service pistons have the same nominal weight and may be intermixed without affecting engine balance. If necessary, used pistons may be fitted selectively to any cylinder of the engine, providing the pistons are in good condition and the same weight. Do not cut oversize pistons down or the engine balance may be affected. Finish hone when selecting the piston.
19. Measure the piston diameter for size with a micrometer or caliper at a right angle to the pin center line, across the skirts, 38 mm (1.50 in) from the top of the piston.
20. Replace the piston if worn beyond specifications or if damaged. Replace the piston with a standard or oversize piston.
21. Use J 8087 to measure the cylinder bore.
22. Rebore and hone to size if necessary. Use the following procedure to hone the cylinder bore to the correct size. 22.1. Select a piston. 22.2. Hone the cylinder bore to obtain the recommended clearance. 22.3. Clean the piston and cylinder bore with soap and water. Dry the cylinder bore and piston. Lubricate the cylinder bore with clean engine oil.
23. Use the following procedure to measure the piston-to-cylinder bore clearance. 23.1. Subtract the piston diameter from the cylinder bore diameter to determine the piston-to-bore clearance. 23.2. Compare the piston-to-bore clearance using the specifications to determine if the clearance is in the acceptable range. 23.3. If the used piston is not acceptable, a new service piston may be selected. Only one oversize service piston is available.
24. When a piston has been selected, mark the piston to identify the cylinder for which the piston was fitted.
25. Select a set of new piston rings.
26. Install each ring, one at a time, into the corresponding cylinder.
27. Install the piston for that cylinder, upside down (top of piston pushing on the ring) and push the ring to approximately 25 mm (1 in) down from the deck surface.
28. Remove the piston.
29. Measure the ring end gap with a feeler gauge.
30. If the ring gap is not within the specification range, replace the rings.
31. Measure the piston ring side clearance (compression rings). NOTE: The piston ring groove must only be cleaned with a ring groove cleaning tool. Proper engine performance and durability depends on the straightness and smoothness of the ring groove. Cleaning the piston ring groove with an improper tool can damage the piston ring groove and effect the performance and durability of the engine.
32. Use the following procedure to measure the compression ring side clearance. 32.1. Roll the piston ring around the groove. 32.2. Measure the side clearance with a feeler gauge. 32.3. If the ring is to tight, inspect the piston ring groove for nicks, burrs, or damage. Use emery cloth to remove any minor burrs. 32.4. If the ring side clearance is greater than the specification, replace the piston.

Camshafts Cleaning and Inspection

Tools Required

J 7872 Magnetic Base Dial Indicator Set

Scheme 866

Scheme 867

1. Clean the camshafts with cleaning solvent.
2. Inspect the camshafts for the following conditions: Scored camshaft journals Damaged camshaft lobes Damaged camshaft sprocket locator pin slots Damaged threads
3. Measure the camshaft lobes using a micrometer. The intake camshaft lobes should be a minimum of 41.5 mm (1.635 in). The exhaust camshaft lobes should be a minimum of 41 mm (1.615 in).
4. Use J 7872 to measure the camshaft runout. 4.1. Set the camshaft in V-blocks between the centers. 4.2. Measure the intermediate camshaft journal.
5. Use J 7872 to measure the camshaft lobe lift. 5.1. Lubricate the camshaft to V-block contact areas with engine oil. 5.2. Set the camshaft on V-blocks. 5.3. Measure the camshaft lobe lift.
6. If the runout or camshaft lobe lift is not within specifications, replace the camshaft.

Scheme 868

1. Inspect the timing chain sprockets for cracks or teeth that are worn, broken, or chipped.
2. Inspect the timing chain for binding or stretching.
3. Inspect the dowel pins for wear or damage
4. Inspect the crankshaft sprocket keyway and the locating dowel pins in the crankshaft for damage.
5. Inspect the timing chain shoe and guide for excessive wear or cracks.
6. Inspect the timing chain tensioner for damage.
7. Replace the timing chain and sprockets if damaged.

Scheme 869

Scheme 870

1. Clean the valve rocker arms and valve lash adjusters in cleaning solvent.
2. Dry the valve rocker arms and valve lash adjusters with compressed air.
3. Inspect the valve rocker arms for the following conditions: Excessive wear at the valve contact or valve lash adjuster socket area A loose or damaged pin A worn or damaged roller. The roller should rotate freely with no binding or roughness. IMPORTANT: Keep the valve rocker arms and valve lash adjusters in the order from where they where removed.
4. Inspect the valve lash adjusters for the following conditions: Excessive wear Clogging of the oil passage Damage Collapsed or spongy

Cylinder Head Cleaning and Inspection

Tools Required

J 9666 Valve Spring Tester

Scheme 871

Scheme 872

Scheme 873

Scheme 874

1. Inspect the cylinder head gasket and the mating surface. Inspect for leaks, corrosion, and blowby.
2. If the gasket failed, determine the cause. The following conditions may cause gasket failure: Improper installation Warped cylinder head Missing or not fully seated dowel pins Low torque on the cylinder head bolts Incorrect length cylinder head bolts A warped engine block surface Scratched surfaces Foreign material Cracked engine block threaded holes
3. Clean the following components: The gasket surfaces Do not use a motorized brush on the head gasket sealing surface. Valve stems and valve heads The bolt hole threads Remove all dirt, debris, or threadlocking material from the bolt holes.
4. Inspect the cylinder head mating surfaces for flatness. Use a feeler gauge and a straight edge.
5. Replace the cylinder head if warped more than 0.08 mm (0.003 in).
6. Inspect the cylinder head for cracks. IMPORTANT: Do not attempt to weld the cylinder head. If the cylinder head is damaged, replace the cylinder head. Minor nicks may be repaired with a fine flat file or emery cloth.
7. Inspect the cylinder head deck for corrosion.
8. Inspect the valve springs for squareness.
9. Use J 9666 to measure the valve spring tension. Replace the valve spring if the tension is not within specification.
10. Inspect the valve guides for wear. The valve guides may be reamed oversized 0.075 mm (0.003 in) and oversized stemmed valves may be installed. The same size valve seal should be used.
11. Inspect the valve seats for excessive wear, damage, or hot spots.
12. Use the following procedure to measure the valve seat concentricity: 12.1. Lift the valve off the valve seat. 12.2. Apply a dab of blue dye to the valve face. 12.3. Seat and rotate the valve. The blue dye traces transferred to the valve seat are an indication of concentricity of the valve seat.
13. Use the following procedure to measure the valve runout: 13.1. Clean off the blue dye. 13.2. Apply blue dye to the valve seat. 13.3. Seat and rotate the valve. 13.4. The traces of blue dye transferred to the valve indicates valve runout.
14. Replace the head if the valve seats are damaged.
15. Inspect the valves for the following damage: Grooving (1, 2) Bent valve stem (3). Replace any bent valve. Burrs or scratches (4). Minor burrs or scratches may be removed with a fine oil stone. Chipped or worn key grooves (5). Replace if damaged. Valve tip wear (6). Replace if worn.