Lvgta

I'm hoping you guys can help. I have an 88 GTA with 4 wheel discs. When you apply the brakes initially, the pedal is hard. It feels like drum brakes and at stop signs, it goes to the floor before it stops. I replaced the rotors and the pads. Did nothing. Took it to Midas. They said master cylinder and booster. Replaced those, still the same problem. What else can it be??? Thanks to anyone that can help or offer insight.

tunatrky

Properly done drum brakes feel great. My dad has a '70 Dodge Challenger that suffered total brake catastrophe from many MANY years of daily driving. We rebuilt his brakes and they stop like new. The pedal is more sensitive and decisive than my '83 Trans Am, and I just put on new rotors, calipers, soft brake lines and pads all the way around on the Trans Am.

Now, I have 4 wheel discs like you. My brake system sounds just like yours but I haven't put in the new booster and master cylinder yet. Also, mine doesn't sink all the way to the floor, but if you pump it a few times it grips nice and hard. Sounds like air in the lines, right? My brake booster doesn't make any air-whooshing noises while engaging the brakes.

I'm thinking these things aren't getting bled properly, it feels just like air in the lines and I verified my booster is in working order. I got my car like this, so I can only assume previous owner let the MC run dry and it needs to be bench bled, but I am no brake expert.... Yet! Do you have ABS? I'm unsure of that year. Bubbles can get caught in the ABS system, if so.

I hear the master cylinder has a small button on the bottom which needs to be pressed the entire time the rears are being bled. I did try this method when I first bought my car. Sure enough, my pedal began to have more pressure. I only bled the front brakes to get it stoppable again, about 10 bleeds per side. I'm going to try a gentle bleed.. Slowly press the pedal down, bleed, release pedal. Small bubbles can develop in the lines from rapidly pumping the brake pedal, and just being generally too aggressive [The person pumping the brakes].

Now, you have put in quite a bit of $$$ and time to even reach this point and your brakes are still no good. Just like me, minus the brake booster & master cylinder. The rod in our brake boosters is not adjustable, so I doubt that could be effecting it. Did they bench bleed the master cylinder correctly? [I'm assuming so, but you never know]. What kind of vacuum pressure are you getting at the brake booster? Check valve in good shape? Have you manually verified each caliper is building pressure and stopping the rotor? Are there any cracked soft lines? They can create bubbles and rob pressure from the caliper. New rotors and pads have a break-in period of 500 miles or so. You're not supposed to do any hard braking during this period and the braking system should begin to grip more. I haven't even put 10 miles on my new brakes yet. My car is now drivable, and stoppable, but I still have too much 'give' in the pedal.

I'm hoping to thoroughly bleed this system tomorrow. I'll report back with any findings.

tunatrky

I am not sure, but I wish there were a way for my to bench-test the brake system instead of driving around town like an idiot. Some sort of pressure gauge to hook up to each brake line. Start the car, begin braking, and see 1] How fast pressure builds and drops off 2] Total pressure applied. That would give us a good insight as to how the system is doing. There's also a proportioning valve but I know nothing of it. I've read quite a few posts of problems like ours. I'm hoping to remedy this at any cost

Lvgta

There is good vaccum pressure at the booster. I'm not sure how much they wer bled and the soft parts look good from the outside. My symptoms are very similar to what you describe on yours. Hard pedal, pump them a few times and they stop ok, but still shaky at stops signs/lights. 1988s didn't come with ABS. I think that came around on 4th gen, but I'm not sure. Thanks for your input. I'm still trying to figure it out.

Lvgta

So I took the car to Firestone Tire and Brakes and they said everything is fine that there is an adjustment on the master cylinder that needs adjusted but that the whole thing would need to come out again to do and it would cost a couple hundred bucks for them to fix it. This sound right to anyone?

alex722607

iTrader: (3)

Bleed the lines just to be sure. Start with RR and open the bleeder screw til fluid comes out, next to RL, then FR, then FL. I just did the prop valve on my car and had some air in the lines. My dad took 10 minutes and bled it like I just described. Works fine now.

Bob88GTA

iTrader: (2)

Get rid of the old rubber lines at the calipers and go to braided lines if you haven't done this already. They are 26 years old. The rubber starts to deteriorate from the inside and expand upon applying the brakes.

Lvgta

Hey guys,

So I've put new rubber hoses on, master cylinder, brake booster, new pads and rotors, and my car still doesn't stop well. I ordered a proportioning valve from Summit Racing, but the part they said fits, is too shallow for my lines. Any ideas on where to get an original proportioning valve for an 88 GTA with four wheel discs? Thanks for anyone that can help.

alex722607

iTrader: (3)

part number 172-2005

its an ac delco part

they can be found on amazon for like 70 bucks or so

Lvgta

Thank you for your help. I was able to get the correct proportioning valve with your help. It still hasn't helped the braking. Any other suggestions out there? We did booster, master cylinder, hoses, proportioning valve, front disc pads and rotors. Bled all lines. Jacked car up and made sure all calipers squeeze. I want to scream.

TTOP350

iTrader: (8)

Are the rear calipers working properly? Not leaking? Not frozen up?

sofakingdom

iTrader: (1)

Replace the rear calipers. DO NOT just jam them onto your car. Install the "recall kit" into them.

Also modify the proportioning valve.

Those 2 things will get rid of a GREAT DEAL of the crappiness of your crappy Deloc-Moraine crap. (did I mention "crap"? if not, please be aware, those rear brakes are The Crap) Won't really make them "modern" or "competitive" but might at least get rid of some of the crappy Stone Age crap crappiness about them.

Search this site for detailed instructions, part #s, etc.