First off the car is a 88 GXL non abs model. I have not had any issues with the braking system since I bought the car two years ago. I have changed the pads before but I have never changed the brake fluid. For a while now I have been hearing a light clicking sound while braking but assume that it may be springs missing on the front caliper. Fast forward to yesterday, I go get two brand new tires and get them installed and watch the installation. Everything is great and car drives as smooth as butter. I get home and then start to leave 30 mins later and come to find out the brake pedal goes straight to the floor when I pull out. I pump the brakes and it gets stiff then it slowly goes to the floor. I figure ok, the master cylinder died, so I swap it out with another unit and bleed the brakes. So thinking everything is good to go i hop in. First stop sign everything is great. Second stop sign I fly past it with the brake pedal to the floor. Go back home and look things over again. No leaks anywhere and master cylinder still full. I go pull the master cylinder and brake booster off my 91 vert non abs. This was a running car that I drove home so I know that both parts were working. I get everything installed but ran out brake fluid. Now its 11:00 pm and I call it quits. Today I finish up and bleed the brakes. Pedal still slowly sinks to the floor and now the car trys to die when the pedal is pressed. I change the hose with the check valve and it seemed to fix the stalling issue but the brake pedal still slowly sinks to the floor. So I go bleed the brakes again and go through 3 bottle of brake fluid. Nothing but clean clear fluid out of the calipers and no air in the line. Tried it again and it still does the same thing. So I swap the proportioning valve or whatever its called and bled the brakes one more time. Now the pedal randomly goes to the floor rather than sinking. For example while driving sometime it will brake normally, nice firm pedal with quick stopping and then the next I press it the pedal goes to the floor and the car keeps going.

I am now at a loss and no longer have any idea what to change out. I am not leaking fluid anywhere. Although all the parts I put on the car they came from my previously working vehicles so I don't understand how everything I swapped in could be bad. Is there something else in the braking system that would cause these symptoms. I am at the end of my rope and am forced to drive this death trap to work so hopefully I can find a quick solution with some help.

Thanks in advance,

 

You put used junk on your car and your suprised its not working?

I would pull the mc apart and verify it was the problem. Also, you could be leaking into the booster and or down the inside of the firewall into the carpet.

If you want better results from putting used break parts on your car become a better mechanic or umm.... dont put used break parts on your car. There are some people I like who drive on roads and stuff and you causing their death would really suck.

 

If I pulled the part from a car that has been sitting for years then yes I understand. This vert I drove here maybe six months ago or less and it was perfect. I took both the master cylinder and brake booster from it the second go around. The first master cylinder might have been shot but this one no chance unless it died from me removing it... When I get the cash to buy a new one I will but I have one more question. I get the new one bench bled, then installed and I have the same issue. What else in the system could cause it or did I kill a brand new master cylinder just by it coming in contact with my hands?

Also as I said before there are no leaks at all. Not me losing fluid but can't see where is coming from. The master cylinder stays full. Firewall dry, inside the car and out since the I suspected the 1st master cylinder was bad. Three master cylinders later no fluid on the firewall or booster but pedal still sinks.

 

Made it to work with no real issues, During break I left to go to the gas station and now a new problem has come up. As the car rolls there is a loud grinding sound coming from the left wheel. Almost sounds like worn brake pads metal to the rotor. If I get on the brake the sound goes away but as soon as I release the brakes its grinding again. My brake pads are fine so I know that isnt it. Im thinking could the caliper possibly be stuck or something. I have never had this issue before and it seems like problems just keep piling up on top of each other.

 

did you check the brake booster vac line? Maybe your booster died.

maybe it's a caliper, but it seems unlikely if you're not losing fluid. if a caliper seizes, only ONE at a time will seize. what you're describing is the whole system.

 

I think the booster is working because the pedal is not hard to use. If I start the car with my foot on the pedal and it does drop as it should. Im wondering if the issue I had at the beginning lead to this loud grinding noise that I am hearing or if it was just something else getting ready to fail. Maybe im having wheel bearing issues....

 

if you have a parts car sitting right there... why not try swapping brake boosters to eliminate that as a cause?

it sounds like you might have more than one problem though, that grinding noise is definitely not the brake booster lol.

 

make sure the pads are not locked up in the caliper and the slide pins move freeley.

there is also a seal that sits in between the master cylinder and the booster. if that is missing you will have no pedal

 

I already swapped brake boosters as well as two master cylinders. I'm confident that the booster isn't an issue at all at this point.


There was a paper gasket between the brake booster and firewall but I do not remember seeing any kind of seal between either booster and master cylinder I had on the car. I have braking ability just not all the time. For example the brakes act normally with good stopping for about 4 times out of 10 depending on how frequently I brake. I am going to try to get a jack at lunch and check things out further.

 

ok my bad, the seal is built into the booster on this generation.

 

Oh, I see.

 

Could you have a soft line that is expanding but has not burst? Not much expansion is needed to totally hork up you pedal.

If you have a grinding noise on one of the wheels why dont you take the wheel off and investigate? Spining it by hand should show what the problem is.

How are you bleeding the breaks, what order, start with right rear, then left rear, then right front, then left front, repeat till you have pedal.

Use a partner so you can see whats happening.

Spin each rotor with a prybar and check that the break is actually clamping down hard enough to stop you from turning it.

Dont leave your driveway if your breaks are not working.

 

LUNCH UPDATE!!!!!

Clocked out and jacked up the car. The front wheel that was making the grinding noise is completely loose. Took the wheel of and the dust cap covering the nut for the bearing and it is practically just sitting there. Tightened it up and no more grinding noise. I will replace both wheel bearing here in the next two weeks so this should do for now.

GregW the comment you made about the line could be possible. The one to the front driver side looks cracked really bad in a bunch of places but it does not leak fluid anywhere. As far as bleeding goes it was done properly and with a partner yesterday and the day before. As mention earlier I do have pedal but only about 40% of the time. The rest of the time it still has braking ability but I have to use a lot more pedal travel practically down to the floor or maybe a inch away from full pedal travel.

 

Try isolating it to a specific wheel by turning each rotor with a pry bar while the breaks are applied. One may be worse than the others.

 

ok, will give it a shot when I get a chance.

Thanks

 

Got home and took the drivers side hub off and the rollers on the bearing fell everywhere. So I think I was right on the grinding noise. I replaced the hub with one from the convertible and it looked great on the inside. Put it on and guess what... No more grinding, no wobbling, and most of all my brakes have been working perfectly everytime. Feeling pretty good now. I will see if it holds out tomorrow.