QuestionTo open, thanks for your help.
I have a 93 GMC Safari AWD EXT van with 165K miles, purchased new. Front disc pads/rotors have 5K on them. Rear drums/shoes are new. I replaced the rears as I heard a clicking sound out of rear LH. Both rear brakes didn't need replaced but did anyway due to clicking sound and I was there anyway. The RH rear drum/shoes R&R'd just great. With the LH rear, I had to shorten the shoe adjusting screw all the way to get the drum to slip over, and even then then it dragged when you turned the drum by hand. I ran it thinking it would wear in but the van pulled badly to the right when brakes applied (assume LH rear brake isn't working properly). The clicking sound was still there as well, coming out of the LH rear brake. I ran it for 500 miles, still pulled to the right & made clicking sound so I again replaced the LH rear shoes, thinking they were faulty not to spec. No change. Still had to shorten brake shoe adjusting screw completely to assemble, van still pulls to the right when braking and makes clicking sound when brakes are not applied. This sound appears to go away at higher speed but hard to tell with road noise at higher speeds. And now when I brake fairly hard with van the ABS light comes on, the pedal goes 1/2 way to the floor, I get a "buzzing sound" out of the dash and braking performance goes to almost nothing. I let off the brake, reapply and they work but still pulling to the right.
Could I have a stuck brake cylinder on the LH rear brake and that's what causing all of this? Could a failed rubber brake line (collapses internally) be causing this?
Looking forward to your thoughts and again, thanks.
AnswerHi First I would crack the bleeder screw on the Left rear wheel cyl and see if the brakes release on that Left rear.
Then, I would check the fluid flow through the LR wheel Cyl. just like bleeding it. See if you getting good flow and pressure. If so, it could be a rubber hose, except it would probally be affecting both rear brakes as they are fed by 1 hose into the meter valve then break into 2 steel lines (located on rear differential). (I believe, not very familiar with AWD L van platform) Does sound like the left rear is staying applied. The brake metering/proportioning valve can also cause this if it is stuck all the way to one side, the other will not get any fluid.
Here is the exact explanation:
These vehicles use either a two function or three function combination valve.
The two function combination valve consists of a metering valve and a brake failure warning switch. The hydraulic brake lines are routed through this valve to the wheel cylinders or calipers. The metering portion of this valve assists in providing balanced front to rear braking by delaying full hydraulic fluid pressure to the front disc brakes until the rear drum brakes overcome return spring tension and the linings contact the drums. The brake failure warning switch portion of the valve activates the brake warning lamp when there is a loss of pressure in either the front or the rear braking system.
The three function combination valve consists of a metering valve, a brake failure warning switch, and a proportioning valve. The metering valve and brake failure warning switch operate the same as those in the two function combination valve previously described.
The proportioning section of the valve proportions outlet pressure to the rear brakes after a certain rear input pressure has been reached, preventing rear wheel lock-up.
Just a suggestion from experience.
Good Luck
Paul
