HEIGHT SENSING BRAKE VALVE ADJ PROPORTIONING VALVE ADJUSTMENT
SUBJECT: HEIGHT SENSING BRAKE PROPORTIONING VALVE ADJUSTMENT PROCEDURE (SERV. INFO.)
VEHICLES AFFECTED: 1991 C3 5000 HD
The following service procedure describes how to adjust the height sensing brake proportioning valve on 1991 C3500 HD trucks.
The procedure should be used whenever the height sensing linkage has been disconnected from the height sensing brake proportioning valve during routine service. This adjustment is made during assembly on all 1991 C3500 HD trucks.
SERVICE PROCEDURE:
Note: Always make sure that the brakes are operational after performing brake work and before returning the vehicle to service.
o Raise vehicle, axle must be allowed to hang free (no load condition).
o Remove nut and disengage lever assembly from valve shaft, as shown in Figure 1.
o Rotate valve shaft to permit installation of plastic adjustment gage. Centre "D" shaped hole of gauge must seat over "D" shape of the valve shaft and gauge tang must be positioned in valve mounting hole, as shown in Figure 1.
o Reinstall lever assembly to the valve shaft utilizing a "C" clamp or channel lock pliers to seat lever nylon bushing to serration on the valve shaft.
Important: Do not drive the lever onto the shaft using the attaching nut. Doing so may result in improper valve setting.
o Reinstall valve shaft nut and torque to 8 - 11 N.m. (70 - 98 in.lbs.)
o Cut gauge tang from body of the adjustment gauge to allow the valve assembly to rotate freely.
o Lower vehicle and test brakes.
SERVICE PARTS INFORMATION
Part Number Description Quantity Required ----------- ------------- ------------------ 15592484 Gauge 1
Part is currently available from CANSPO.
BRAKE BURNISHING
o On dry clean level roadway, accelerate to 90 km/h (55 mph.), observe traffic following and when its clear
o Apply brake at a deceleration rate of 2.5m (8 ft)/sec/sec until vehicle speed is 40 km/h (25 mph). A decelerometer must be used to achieve the proper deceleration rate.
o Repeat this procedure at 1 mile intervals 15 times.
Decelerometers are available from various sources:
If a decelerometer is unavailable the braking should be of a constant application bringing the vehicle speed from 90 km/h - 40 km/h (55 mph 25 mph) in approximately 5-6 seconds.
ONTARIO: U.A.P MISSISSAUGA 416-625-6200 UNISELECT DOWNSVIEW 416-638-8377
QUEBEC U.A.P. MONTREAL 514-256-5031 R-BEC MONTREAL 514-643-1130 UNISELECT MONTREAL 514-641-2440 PRO BEC MONTREAL 514-324-4111
BRITISH AUTO MARINE VANCOUVER 604-874-7333 COLUMBIA: ELECTRIC AUTO MARINE BURNABY 604-294-4944 ELECTRIC VIKING VANCOUVER 604-526-8265 REMA TIP TOP VANCOUVER 604-253-4196
ALBERTA: JOHN BRAY EDMONTON 403-487-3509 ALBERTA SALES EDMONTON 403 -279-8212 KENNAN EDMONTON 403-387-3021 EQUIPMENT
SASKATCHEWAN: AUTO ELECTRIC REGINA 306-525-2551
MANITOBA: FORTH IGNITION WINNIPEG 204-633-9600
NEW BRUNSWICK: COMMERCIAL ST JOHN 506-648-2200 EQUIPMENT U.A.P. MONCTON 506-857-1111
NOVA SCOTIA: COMMERCIAL 902-494-5400 EQUIPMENT
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.
