I have a '91 camaro (140,000 miles) that used to have the stock disc/drum brakes. This winter I swapped in a Borg Warner posi rear end with 3.27 gears and disc brakes (the iron Delco-Moraine disks).
I replaced the hard and rubber lines on the new axle and bled the rear lines; however when I went to drive the car, the pedal went to the floor and the brake light on the dashboard came on. There are no signs of leaking brake fluid, so I don't think air is getting into the system.

So I have a few questions:

1. I have read conflicting information on whether the stock proportioning valve from my '91 will "work." Has anyone else experienced the brake pedal going to the floor using a proportioning valve for a disk/drum setup on a disk/disk setup?

2. I also realized my master cylinder could have gone out after bleeding the brakes, so I installed a new master cylinder today, but I am waiting on new front brake calipers; so I don't know if the master cylinder was the problem yet. What do you guys think?

3. Could one of the rear calipers be stuck and cause the brake pedal to travel to the floor?

Thanks,

Scott

 

something don't sound right. i would rebleed the system. watch the brake fluid level in the master so it don't go empty.

 

Is the Pressure Differential Switch light on? If so, it's alerting you to a leak in one of the brake circuits.

While the drum/disc combination valve will work, remember that GM designed three valves--disc/drum, disc/disc, and 1LE, each I believe with increased bias--so the correct valve for your application is a wise choice, IMO. Your 91, IIRC, has the second design combination valve, which means that a standard disc/disc valve won't bolt up. You might try an adjustable.

Here's the shop manual's recommendations for Excessive Pedal Travel:

1. Partial brake system failure (Check both front and rear system for a failure and repair. Also check warning light. It should have indicated a failure).
2. Insufficient fluid in master cylinder (Fill reservoirs with approved brake fluid. Check for leaks. Check warning light. Bleed system).
3. Air trapped in system (Bleed system).
4. Rear brake not adjusting (Adjust rear brakes and repair auto adjusters).
5. Bent shoe and lining (Replace axle set of shoes and lining.

JamesC

 

I put new front calipers on both sides today ($10.99 ea) and when I was bleeding the drivers side, almost no fluid was coming out. So I think maybe the brake hose has failed; so I ordered new brake hoses for each side and I should have them tomorrow.

Hopefully all the problem is a bad hose. I will keep everyone updated.

 

Still getting the brake light on and a soft pedal. I replaced everything up front and all the brake hoses on the entire car.

Tomorrow I am going to rebleed the rear brakes again. It seems like I am able to push the piston inside the rear cylinder back with my bare hands even with the bleeder screws tightened. I have never been able to do that on any disc brakes before. Something just is not right. Maybe I have a defective brake cylinder.

 

Okay, I solved the problem. When I swapped in the axle from the '87 Iroc, I did not realize you had to raqchet the bolt to adjust the piston stop. After moving the lever back and forth, I got pressure and the brake light went off.

The brakes feel okay, but the pedal is not as firm as I would like it to be. Do the adjuster screws have a tendency to back themselves out? After driving for ten minutes, I lost brake pedal pressure, but it came back a little later after moving the lever again.

 

dam dude i have the same problem.i swapped in the rear out of my old 88 iroc into my 91 shell. the brakes worked reall nice for the first 3 or 4 months,and then the brake light started coming on on the dash.it got worse over time.now i can put the pedal rite to the floor. when everything was swapped i swapped the master and the prop valve.i just recently replaced both those parts again and it is still doing the same sh**.i cant figure it out.been bleeding the brakes out for 3 days now. as soon as it starts to feel like they are fixed,10 minutes later im putting the brake pedal to the floor again.

 

can you explain about that piston stop adjustment some more? i'm planning to swap from my drum 2.73 open 10bolt to a disc 3.27 9bolt out of an '87 too!
thanks

 

I guess the best way to explain it is like this: The piston inside the brake caliper pushes against the brake pad which pushes on the rotor, but after reducing pressure on the brake pedal, the piston inside the brake caliper should only move back like a 1-2 cm. However, due to weak springs or low pressure, the piston moves back like 3-4 cm. It now takes more pedal travel to make the piston move to make contact on the brake pad.

After I manually moved the the racheting arm on the back of the brake caliper, the piston hits a "stop" and could only travel back the 1-2 cm; causing less force on the brake pedal. I have been driving my camaro for several months and have not had any problems with the brakes. I think I just got used to the slight sponginess of the brake system.

 

Maybe a dumb question, but did you bench bleed the master? If you let al lthe fluid run out of it when changing the rear, you would need to bench bleed it and that may remove the sponginess for you.

 

I basically rebuilt the entire brake system. I replaced the master cylinder (and I did bench bleed it). I also replaced all the hard lines and soft rubber lines.

 

Same kind of spongee pedal feeling. I have a 4th gen rear with 3.42 gear. After bleeding the front brakes I have some pressure and the car stops fine but it feels too soft. Has anyone resolved this issue yet?

 

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