I have spent the past two days searching through old forums on here trying to see if its been covered before. People on here have had the same problem I have but no one really has offered any solutions.

I have a 1987 GTA with 4 wheel disc brakes. I bought the car from an auction and it had been sitting for years. I had several 3rd gen firebird parts laying around and decided to buy it and replace anything that needed it with the parts I had.

Now I have drove this car for over a year with no problems with the brakes what so ever. I decided to swap the rear end out for a built 10 bolt I had. I did the swap, bled the brakes and had no problems (other than the rear end gears screaming). I pulled the rear end back out and replaced it with the original one till I get time/money to look at whats wrong with the 10 bolt that was screaming. When I switched rear ends I took apart the rear brake lines to switch them over to the 10 bolt. Like I said first go around no problems, bled them and they were fine. Now that Im installing the original rear back in the car I bleed and get a great pedal until I start the car.

So finally we are at my problem, I pump the brakes with the car off and get a real firm pedal. Start the car and lose that pedal and the "brake" light come on the dash. I decided to bleed these darn things every type of way I could think of. I did gravity bleeding,traditional two man bleeding,I used a vacuum bleeder that runs off my air compressor. I bleed in the correct sequence (pass rear,driver rear,pass front,driver front) same outcome. I also disconnected the sensor on the brake valve to make sure thats why the idiot light was on. As soon as its unplugged the light goes off, so I know thats why the light is on.

Today I took it to midas to see if they had any suggestions. They suggested (just like all the forums on here) to replace the master cylinder. The only place that had it in stock was Summit so I rand down there and picked up one along with a MC bleeder kit. Came home bench bled it just fine. Installed it, bled the brakes again and same outcome.

Like I said I have read all the forums on here, I tested the vacuum on the booster and it holds steady around 19-20. check valve is doing its job on the booster as well. And from what I have read if the booster or vacuum was the problem then I would have a firm pedal not a soft pedal.

I know there are alot of upgrade options but Im just looking to get pressure and safety right now, not really a performance upgrade

I am just out of ideas and need to get this fixed fast! Please someone out there has to have had this happen and knows what direction to point me in.
I thank you all in advance

 

Did you ever figure this out? I have the same issue and can't get it sorted out.

 

try bleeding it with the MC loosened from the booster a bit.

I have seen this happen when there isn't enough freeplay, the master cylinder doesn't uncover the compensating ports and uptake fresh fluid properly.

 

Hello All,
Did you figure this issue out? I also have the same problem. I converted my rear drums to disc and haven't had great pedal since. I've gone so far as to replace the brake booster, master cylinder, brake pads, rotors, brake lines and even install an adjustable prop valve on the rear brake lines after the master cylinder.

I've bled the car more times then I can count, both two person and with a pressure bleeder. Not sure where to go from here.
Any ideas, I may try the loosen master cylinder from booster that b_the_j posted.

Thanks

 

Did you "bench bleed" the MC?

Gotta remember, it sits at SUCH an angle on our cars, that it makes a little "chamber" up above where the lines connect; with the end result being, air is trapped up high there, with NO WAY to get out when the MC is on the car. You can bleed 1000 gallons of fluid through it every single day, and twice on Sundays just for good measure, and that air will STILL be trapped up in there and you will STILL have a low soft squishy pedal.

The MC MUST be held level and all that air bled out of it, BEFORE mounting it to the car.

 

Yes, I bench bled the MC. Probably pumped it about 70 times until all the air was out, but when mounting this to the booster you end up loosing a little brake fluid when screwing your brake lines into the MC.

Do you think a little air got into the MC during this process? If so, do you remove this through bleeding the brakes or do you loosen the lines at the MC while a friend pumps the brake to release that air at the MC?

Another question that I've been wondering. Do you think the bore size on the MC could be off from stock since I've upgraded to disc in rear from drum? I came across some info that said GM used the same MC if the car had drums or disc, not sure how true this is?

Thanks

 

Definitely possible.

Depends on where the air is at tha tpoint. If it's in the lines, it'll bleed out. If it's in the cyl, you're farkled, and have to "bench bleed" all over again.

Always seems best to use those plastic fittings and aquarium tubing fragments they give you, and leave the ends of the tubing submerged in the reservoir during assy, and only remove the plastic fitting at the absolute last possible instant before hooking up the line. Helps to straighten the line before any of this, such that you can thread the line nut up into the casting QUICK with your fingers, rather than leaving it randomly bent to where you struggle with getting it started and then having to tweeeeeek it on one flat at a time with a wrench.

 

did you check proportioning valve , sometimes they stick , will make tight come on ? can affect brake pedal feel also. good luck

 

trevorwelk,

I ended up getting so frustrated that I took it down to my local Pep Boys to see if maybe they could vacuum bleed it and check the pressure in the system.

They had a mechanic there who happens to have a 3rd gen GTA just like mine. He knew EXACTLY what it was. There was a recall on our rear brakes apparently. He even had the part number for the recall kit to correct the issue. What happens he said is the calipers suck air and wont allow the system to bleed correctly. He took me into the shop and showed me what to do while the car was on the rack. He just used a flat screw driver to hold the caliper piston out then crack the bleeder. He did it to both rear calipers and BOOM i have pedal again. He said it could end up sucking air again in a day a month or maybe never but thats why he wanted to show me what to do, so I dont have to pay pep boys again.

So again here is what he said to do and it worked perfectly!
1- Have someone pump the brakes inside the car until pedal builds pressure.
2- Have them hold pedal down and use flat head screw driver to hold caliper piston out completely
3- Crack bleeder, close bleeder once pedal hits floor.

All standard two person brake bleeding procedure but adding that step with the screw driver. I have had the brakes work fine for over a year now.

Like I said he did give me the part number, its around here somewhere if you need it. But im sure if you just do a simple google search or even a search on here you will find out more about the rear brake caliper recall our cars had.

Hopefully that helps you like it did for me!