SERVICE MANUAL UPDATE SEC. 6A1 (TIMING BELT TENSION ADJUST)

Subject: TIMING BELT TENSION ADJUSTMENT

Model and Year: 1990-91 GEO STORM WITH 1.6L ENGINE

This bulletin is in addition to the procedures located under "Timing Belt" found in Engine Mechanical - 1.6L (Section 6Al) of the 1990 and 1991 Geo Storm Service Manuals (ST371-90 and ST371-91, respectively).

This bulletin gives timing belt adjustment procedures and timing belt deflection specifications.

1. Insert a hex wrench into the tensioner pulley hexagonal hole. Rotate the pulley counter clockwise to tension the belt. Hold the pulley stationary and temporarily tighten the bolt.

2. Turn the crankshaft two complete counter clockwise revolutions and align the crankshaft timing pulley mark on the oil pump (Figure 1).

3. Loosen the tensioner pulley bolt.

4. Insert a hex wrench into the tensioner pulley hexagonal hole. Rotate the pulley counter clockwise to tension the belt. Hold the pulley stationary and tighten the bolt to specification.

Tighten

* Tensioner pulley bolt to 50 N.m (37 lbs. ft.).

5. Move the crankshaft back to about 50 degrees BTDC and to TDC of Number 4 Cylinder. Align the crankshaft pulley timing groove with the mark on the Oil Pump (Figure 1). Make sure that the camshaft pulley timing mark is aligned with the upper surface of the cylinder head and dowel pin is in the up position (Figure 2).

6. Measure the deflection of the timing belt as shown in Figure 3.

7. If deflection is not 16 to 20 mm (0.63 to 0.79-inch) with 98 N.m (22 lbs.) of pressure, readjust the timing belt. Check to insure camshaft is still in position (Figure 2).

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.