Century L4-151 2.5L VIN R TBI (1985)
Camshaft Gear/Sprocket: Customer Interest
Engine - Timing Gear Noise (Knock)
Bulletin 87-6-12
Date
May '87
Ref.No.
87-089-6
Corp. Ref. No. 706005
SUBJECT:
TIMING GEAR NOISE (KNOCK)
MODELS AFFECTED: SOME 1985 THRU 1987 MODELS EQUIPPED WITH 2.5L L-4 ENGINES (VIN CODES R AND U)
If an engine has a knock and the preliminary diagnosis is a "cam gear knock", use the normal procedure described in Buick bulletin 85-6-18, to check
camshaft end clearance and gear backlash.
Measure the backlash at positions outside the two retainer plate access holes and at two other areas 90 degrees from these holes.
If end clearance is not beyond .0015" (.0381 mm) to .0050" (.127 mm) and backlash is not beyond .0005" (0.013 mm) to .0095" (0.241 mm) and the
cam and crank gears are not damaged, the gears are not causing the knock. Examine the engine for other sources of knock.
If end clearance is less than .0015" (.0381 mm), replace the spacer ring; if it exceeds .0050" (.127 mm), make certain the gear is seated properly against
the spacer, and if it still exceeds .0050" (.127 mm), replace the thrust plate.
If backlash is less than .0005" (.013 mm), or greater than .0095"(.241 mm), replace the cam and crank gears.
