SERPENTINE BELT SQUEAK SHIM A/C COMPRESSOR BRKT.

VEHICLES AFFECTED: 1987 S/T TRUCKS WITH THE 2.8L V6 ENGINE AND C60 AIR CONDITIONING

Some 1987 S/T trucks with the 2.8L V6 engine and air conditioning may experience a squeaking noise from the serpentine belt. This condition may be caused by a belt misalignment between the A/C compressor and the belt idler pulley. The belt misalignment causes the belt to rub against the front or rear inner edge of the A/C pulley groove, creating the squeak. If this condition is encountered, it can be corrected by shimming the A/C compressor mounting bracket.

Vehicle Inspection

With engine idling, inspect the belt as it goes from the A/C compressor to the idler pulley. The belt must be straigit between these components (See Figure No. 1). A misaligned belt will be at a slight angle in this area, will run against the front or rear inside edge of the A/C pulley, and will run on the inside or outside edge of the idler pulley. (A straight belt will be centered on the idler pulley.) If the belt is misaligned, use the following procedure.

Procedure

1. Shut off engine.

2. Locate the A/C compressor mounting bracket bolts (See Figure No. 2).

3. Using a 16 mm socket and rachet, remove the tension from the belt tensioner by rotating it to the left (counter clockwise) and remove the belt from under the idler pulley (See Figure No.1).

4. Loosen the three A/C compressor bracket mounting bolts.

5. Install one (1) 1/32" thick front end (caster camber) shim between the bracket and the cylinder head (See Figures No. 2 and 3). NOTE: Some trucks were built with the shim in production and it may be necessary to remove the, shim to correct belt angle. If the shim used has a tab on it (many Eront end shims have a tab at the top to allow for easy assembly), make sure the shim is aligned so that the tab does not hit the intake manifold.

6. Torque the bolts to 40-60 N.m (30-44 ft lbs), reinstall the belt and retest the truck. The belt should be straight between the A/C compressor and the idler pulley. Itmaybe necessary to add a second shim on some trucks to straighten the belt.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.