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| Pontiac Engine >> TIMING GEAR NOISE
Timing Gear Noise Or Knock On General Motors (Pontiac) 2.5L 1-4 Engines
The following information lists characteristics of timing gear noise to assist diagnosis of problem cases involving the subject engines.
Loose or improperly seated camshaft timing gears are usually loudest when warm. They are sensitive to speed only, not load sensitive. Cam gear noise will be noticed at a warm idle and sounds much like a loose timing chain noise. It is recommended to remove the drive belts and use a sounding device on the timing pointer. This will provide a definite indication of timing gear noise.
Timing gear noise is most noticeable at about 800 rpm. It can be heard the loudest at the timing gear cover and at the oil pan between #3 and #4 cylinders.
If the noise has been diagnosed as timing gear related, Pontiac Motor Division recommends AERA members use the following procedure for checking timing gear backlash:
1. Remove the rocker arm cover and loosen all rocker arm retaining nuts on pre-1981 vehicles and shouldered bolts on 1981 and later models.
2. Remove the timing gear cover.
3. Check the camshaft end clearance to determine if the gear is fully seated. End clearance should be .0015 to .005.
4. Using a magnetic dial indicator positioned on the front face of the engine block, place it on one tooth of the camshaft gear. Be certain that the crank gear hub is torqued.
5. Rotate the camshaft gear back and forth. Camshaft gear backlash should not be less than or exceed .0005 to .0095.
6. If the camshaft end clearance is over .005 or gear backlash exceeds .010 over the above limits, the timing gear and/or thrust plate should be replaced.
The AERA Technical Committee
September 1983 - SB 105
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