Safari Van M V6-262 4.3L (1985)
Brake Proportioning/Combination Valve: Technical Service Bulletins
Brakes - Improved Loaded Vehicle Performance
GMC NUMBER:
87-T-116
GROUP:
5 - Brakes
DATE:
December, 1988
CORPORATE
NUMBER:
665005R
SUBJECT:
IMPROVED BRAKE PERFORMANCE
MODELS:
1985-1987 M VANS
THIS BULLETIN CANCELS AND SUPERCEDES TRUCK SERVICE BULLETIN 86-T-136 DATED FEBRUARY, 1987, ALL COPIES OF
WHICH SHOULD BE DISCARDED. THIS BULLETIN IS BEING REVISED TO INCLUDE SOME 1987 MODEL VEHICLES.
Safari/Astro vans are designed to carry varying loads, and therefore, they are equipped with brakes that are capable of good stopping performance under
a variety of conditions. Some customers who operate their Safari/Astro vans heavily loaded most of the time may prefer additional rear braking. If so, the
following procedure is an acceptable method of increasing rear braking on 1985, 1986 and some 1987 Safari/Astro vans. It will result in a higher rate of
deceleration at wheel slide and shorter stopping distances in a heavily loaded condition. The customer should be informed that there will be an increase
in rear brake performance and the potential for rear wheel skid in unladen applications. Safari/Astro vans, in both their original condition or as changed
by this bulletin, meet all the stopping requirements of Federal Motor Vehicle Safety Standard 105 for Light Duty Trucks.
Service Procedure
Important:
Care must be taken to prevent brake fluid from contacting any painted surface.
1985-1986 Models:
Always ensure that the brake system is operational after performing brake work and before returning the vehicle to the customer.
FIGURE 1 - COMBINATION VALVE
Steps A, B, and D involve all subject vehicles. Step C is engine dependent.
A.
Replacement of the combination valve, (Figure No. 1)
1.
Disconnect negative battery cable.
2.
Disconnect the four brake lines at the combination valve.
3.
Disconnect electrical harness at the combination valve.
4.
Disconnect combination valve at bracket on the brake booster and discard valve.
5.
Install new combination valve (P/N 15571205).
6.
Reverse above procedure for reinstallation and tighten bracket nuts to 50 N-m (37 ft. lbs.).
