Century Estate Wagon L4-151 2.5L VIN R TBI (1987)
Drive Belt Tensioner: All Technical Service Bulletins
Engine Accessory Drive - Temporary Noise
Bulletin
87-6-3
Date Nov., '86
Ref. No. 87-025-6
SUBJECT:
NEW VEHICLE ACCESSORY DRIVE NOISE
MODELS AFFECTED: 1987 CENTURYS WITH 2.5L (LR8) ENGINE (VIN CODE R) AND AIR CONDITIONING
Some new vehicles, at low mileage, may temporarily exhibit one or both of the following conditions:
1.
A clicking noise coming from the tensioner when the tensioner moves while engine is idling. The tensioner can be confirmed as the cause by
observing the tensioner motion while changing the accessory loading. If the noise is from the tensioner, it will be present when the tensioner moves
at high load, and will disappear when the tensioner stops moving at light load.
2.
A short duration (approximately one second) light rumble that occurs immediately upon application of power to accelerate from a stop. The noise
is most likely to occur under conditions of high accessory load. The rumble is caused by resonance of the belt span between the A/C compressor
and crank pulley. Positive diagnosis of the rumble can be made by installing a non A/C belt, Part No. 10041195, that bypasses the compressor and
eliminates the noise.
Both conditions are caused by variations in tensioner damping during initial operation:
^
The clicking is due to a sticking condition that occurs once most of the grease has been displaced, but before the outer case has been
"polished" by the damping band.
^
The rumble is due to lower than normal damping while a corrosion preventive grease is being displaced from between the damping band and
the outer case.
These conditions will dissipate with continued operation of the vehicle. Most occurrences should disappear within 200 miles. Experience has shown that
the clicking noise disappears within this mileage range. The light rumble, in some instances, may take considerably more than 200 miles to dissipate.
Neither condition has any adverse effect on system function or durability, and replacing parts with those presently available will not alleviate these
conditions.