2007 Chevy Uplander Brakes

[gungfudan]

A friend of mine has a 2007 Chevy Uplander and he changed the front rotors and brake pads and everything was fine. Then a few days after the brakes got really soft. He changed the back pads and bled all the brakes and it is still the same.
What could be the issue? I was thinking maybe the calipers are bad or the rubber brake hose is collapsed but in my experience the brakes have always just locked up. Could it be the master cylinder?

 

[gungfudan]

His brake pressure just came back?!?!

 

[RonD]

There is a gap somewhere

Is the pedal firm after he pumps it, i.e. doesn't keep going down?

Is the brake fluid level in the master staying the same, no loss of fluid?

Did he change the front brakes because they were worn down or was there another issue?

Rear disc brakes are popular, not sure why, lol, but on some models you need a tool to screw in the caliper's piston which is threaded for use as an E-brake
Also hold out E-brake release and pump the e-brake pedal until it firms up, that adjusts the rear pads or shoes

And no ABS light when brakes are used?

You can check the flexible hoses, run your hand over each and feel for a bulge, these can rip internally and allow fluid to expand inside them so soft pedal
One at each front wheel and usually one at the rear axle but can be 2

You can take the cap off the Master and then have some one press down on the brake pedal while you watch fluid in Master
Fluid goes OUT of the master down the brake lines, NONE should come up in the Master

 

[91stranger]

Did he check for pinhole leaks? We had an 07 uplander it those things rust like no other underneath.

 

[gungfudan]

There is a gap somewhere

Is the pedal firm after he pumps it, i.e. doesn't keep going down?

Is the brake fluid level in the master staying the same, no loss of fluid?

Did he change the front brakes because they were worn down or was there another issue?

Rear disc brakes are popular, not sure why, lol, but on some models you need a tool to screw in the caliper's piston which is threaded for use as an E-brake
Also hold out E-brake release and pump the e-brake pedal until it firms up, that adjusts the rear pads or shoes

And no ABS light when brakes are used?

You can check the flexible hoses, run your hand over each and feel for a bulge, these can rip internally and allow fluid to expand inside them so soft pedal
One at each front wheel and usually one at the rear axle but can be 2

You can take the cap off the Master and then have some one press down on the brake pedal while you watch fluid in Master
Fluid goes OUT of the master down the brake lines, NONE should come up in the Master

The fluid is the same level after he bled the brakes. And when they started to work properly again the fluid was still at the same level. He changed the front rotors and the pads because they were bad. The front rotors were warped. The back did take a special tool and he used one on it. But he changed the back brakes after the brakes became soft but they needed to be changed. I have not been there with him due to working out of town. I told him to check for visible bubbles and he did there were none. He has not checked for pinholes in the metal lines.

 

[gungfudan]

So I never said what fixed this. Come to find out that I have been changing brakes all wrong. A friend of mine owns a repair shop and he said that you should always open the bleeder when you are putting new pads on an ABS equipped vehicle. When you depress the caliper piston open the bleeder because the back pressure can cause the ABS valve to get stuck open. He said that this happens rarely but when it does you can slam on the brakes to hopefully get the valve to flip back to normal.

 

[RonD]

So I never said what fixed this. Come to find out that I have been changing brakes all wrong. A friend of mine owns a repair shop and he said that you should always open the bleeder when you are putting new pads on an ABS equipped vehicle. When you depress the caliper piston open the bleeder because the back pressure can cause the ABS valve to get stuck open. He said that this happens rarely but when it does you can slam on the brakes to hopefully get the valve to flip back to normal.

Yes, +1 ^^^

But I was taught that by my grandfather before ABS Brakes, or even disc brakes, lol

Open bleeder to collapse caliper or wheel cylinder, don't try to force fluid back into the system

 

[racsan]

Yes, +1 ^^^

But I was taught that by my grandfather before ABS Brakes, or even disc brakes, lol

Open bleeder to collapse caliper or wheel cylinder, don't try to force fluid back into the system

hell, I never knew that. I do know that with 4-wheel disc all 4 wheels will wear the pads pretty evenly, so Ive always done all 4 corners when doing a car with 4wheel disc. I did do brakes on a uplander this spring, didn’t realize the rears “screw” in, got lucky and the old C clamp I was using had a frozen foot on the screw side, so it inadvertently turned and pushed the piston in. wasnt easy though.

 

[8thTon]

I never knew that either.