SERVICING HYDRAULIC UNITS SERVICE KIT MODIFICATIONS

SUBJECT: INFORMATION ON SERVICING HYDRAULIC UNITS - 1987-1991 ALLANTES

All 1987-1991 Allantes share a common ABS hydraulic unit service kit. Because of changes to the brake pedal and because some vehicles are equipped with traction control, the service kit may require certain modifications. It is important that the following procedures are adhered to when servicing the hydraulic unit.

PUSHROD IDENTIFICATION

The service ABS hydraulic unit assembly, P/N 3527782, is supplied with two pushrods. The pushrods differ in length and hole diameter. 1987-1990 Allantes have hydraulic unit assemblies with Pushrod "A". A quantity of 1,630 1991 Allantes are also equipped with Pushrod "A" as a carryover from 1990. The balance of 1991 vehicles are equipped with Pushrod "B". Refer to Figure 1.

The correct pushrod must be matched with the new hydraulic unit assembly. A mismatched pushrod and pedal will result in a loose or sloppy pedal and necessitate replacement of the hydraulic unit assembly. Once the pushrod is inserted into the hydraulic unit assembly, it is not possible to remove it without damaging the hydraulic unit assembly. For proper matching proceed as follows:

Attempt to install Pushrod "A" on brake pedal pin. If Pushrod "A" fits over brake pedal pin, use Pushrod "A" and discard Pushrod "B". If Pushrod "A" does not fit over brake pedal pin, discard Pushrod "A" and use Pushrod "B".

NOTE: Do not install pushrod into hydraulic unit assembly before installing the unit into the vehicle. Install pushrod onto brake pedal pin and then guide pushrod into rear of hydraulic unit assembly during unit installation. Fully depress the brake pedal to ensure proper seating of the pushrod into the hydraulic unit assembly.

BLEEDER SCREW BANJO FITTING FOR NON-TRACTION CONTROL VEHICLES (THIS APPLIES TO 1987, 1988 AND 1989 VEHICLES ONLY)

Remove the bleeder screw banjo fitting when installing the service hydraulic unit assembly on 1987, 1988, and 1989 vehicles by performing the following steps. Refer to Figure 2.

a. Remove black rubber cap (1).

b. Unscrew bleeder screw (2).

c. Unscrew banjo bolt (3) and remove it together with high pressure fitting (4) and 0-ring.

d. Hand tighten bleeder screw into the port where discarded banjo fitting was. Tighten after bleeding operation. (Tightening torque is 8 to 12 N-m, 6 to 9 lbs. ft.)

BRAKE FLUID RESERVOIR

Traction Control Vehicles:

For 1990 and later vehicles with traction control, cut off traction control hose connection as shown in Figure 3. Before reinstalling the traction control fluid return hose, ensure the newly-cut hole is unobstructed and allows for free flow of fluid.

Non-Traction Control Vehicles:

For 1987, 1988, and 1989 vehicles DO NOT cut off the traction control fluid return hose connection!

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.