Help with Soft 91 Suburban Brakes

[barndoor91]

The brakes on my 91 V1500 4x4 Suburban are soft and lack any authority.

On initial application it feels like the brakes are engaging but additoinal pressure doesn't bring any more brake force. I can stand on the pedal with both feet but can never get the brakes close to locking up. If I hit the brakes very quickly the pedal initially resists depression.

The brake indicator light doesn't come on during braking (works with parking brake and with ignition on).

I've replaced the calipers, disc pads, rear cylinders and pads, power booster and master cylinder. These change had little if any affect.

The problem is more acute from a cold start.

This truck has the rear anti-lock brake system (RWAL). I'm down to the hydraulic componets of the RWAL and possibly the brake lines. Anybody have similar experience or ideas?

Thanks!

[2000CAYukon]

Originally Posted by barndoor91

The brakes on my 91 V1500 4x4 Suburban are soft and lack any authority.

On initial application it feels like the brakes are engaging but additoinal pressure doesn't bring any more brake force. I can stand on the pedal with both feet but can never get the brakes close to locking up. If I hit the brakes very quickly the pedal initially resists depression.

The brake indicator light doesn't come on during braking (works with parking brake and with ignition on).

I've replaced the calipers, disc pads, rear cylinders and pads, power booster and master cylinder. These change had little if any affect.

The problem is more acute from a cold start.

This truck has the rear anti-lock brake system (RWAL). I'm down to the hydraulic componets of the RWAL and possibly the brake lines. Anybody have similar experience or ideas?

Thanks!

How did you adjust the rear brakes? I have a 90 K1500 truck which is basically the same brakes. With the rear end off the ground and in neutral, you should feel the brakes drag as you spin the tires. On my truck, the brakes have to be adjusted with the wheels off.

You can also pump the pedal while driving in reverse but it takes a while to get them as tight as by hand.

I adjust my rear at every tire rotation and the pedal is nice and firm plus I get better wear on the fronts.

//2000CAYukon

[barndoor91]

Originally Posted by 2000CAYukon

How did you adjust the rear brakes? I have a 90 K1500 truck which is basically the same brakes. With the rear end off the ground and in neutral, you should feel the brakes drag as you spin the tires. On my truck, the brakes have to be adjusted with the wheels off.

You can also pump the pedal while driving in reverse but it takes a while to get them as tight as by hand.

I adjust my rear at every tire rotation and the pedal is nice and firm plus I get better wear on the fronts.

//2000CAYukon

Thanks for your suggestion. When the rear brakes were replaced they were carefully adjusted and then most recently after the master cylinder was replaced. I think I read somewhere that the read auto-adjusters (the things that work while braking in reverse) could get worn. Wonder if these things could be basically faulty and allowing the brakes to open up after a short amount of driving?

[2000CAYukon]

Originally Posted by barndoor91

Thanks for your suggestion. When the rear brakes were replaced they were carefully adjusted and then most recently after the master cylinder was replaced. I think I read somewhere that the read auto-adjusters (the things that work while braking in reverse) could get worn. Wonder if these things could be basically faulty and allowing the brakes to open up after a short amount of driving?

Sometimes, the brake shoes have a high spot and need to be readjusted after a short time. You should feel the brakes drag when you spin the wheel. If not, they need to be readjusted.

//2000CAYukon

[777stickman]

If your Sub is equipped with Hydro boost system instead of a vacumn system, I would definately look at the power steering pump as the problem..........Steve

[sub006]

Since front discs were introduced with the '73-'91 body style, they have been marginal for the weight of these vehicles.

I run Earl's braided stainless brake lines front and rear, which take away some of the sponginess.

In 385,000 original miles on my '90, I've tried several brake pads, finally settling on Raybestos Brute Stops (about $50 at Pep Boys). I get at least 50,000 miles (I live in steep hill country) with minimal dust and rotor wear.