I am gonna drive my 90 Vert off a cliff !!!

Awhile back I posted about having a soft pedal after having to do a panic stop and the consensus was that the master cylinder took a dump. I replaced it with a rebuilt unit, bench bled it until I saw no more bubbles, installed it and bled the 4 corners. No brakes - pedal goes right to the floor when engine is on.

Guessing that I got a bad rebuild, I bought a new one, bench bled it while shaking it, tapping on it etc until there were no bubbles, installed, bled the 4 corners and I still have no brakes - pedal to the floor.

I bought a small pressure bleeding rig thinking that maybe air was still in there - bled the M/C, the 4 corners and I still have no brakes!!!

I have gone thru about 2gal of fluid so there is no worries of contaminated stuff in there. I have tried bleeding with both speedbleeders and the OE. I never see any air in the hoses at the corners - just a nice clear tube filled w/ fluid. I know it is moving thru - I have to empty my collection jar quite a bit,

They only oddity I have is that when bleeding the front right caliper, there is quite a bit of resistance - much more than the other 3. Could something be messed up in there?

Could there be anything hokey with the ABS? The "Service ABS" light goes on when I start the car but goes out after a few seconds.

PLEASE HELP ME! This car is driving me mad - my faith in the church of Vette is disappearing

Thanks

 

damn. That ain't right... at all...

Going to the floor... I wonder, any sign of fluid leaking past the pistons? I wonder if you have a bad caliper.

 

Had a similar problem a few years back on an '82 we restored. Breaks went soft, replaced the MC and still had no breaks. Turned out the rear left caliper was bad. Replaced it, bled the breaks and they worked fine -- might want to check them out. Good luck.

 

Well, I haven't noticed any fluid leaking from the rears. I haven't pulled the front wheels off thanks to the clamshell hood. Tomorrow I plan to pull the fronts off and see if I can see anything funky.

I'll check for leaking then pull the hose off and try to determine if there is any kind of blockage. Given the fact that this all started because of a "HOLY S**T" panic stop, a leak would make sence now that the M/C is new.

Thanks all!

 

Can you get the car on a lift or 4 stands?

If you can get it up, have some one apply the brakes, pedal to the floor.

Then try and and turn each wheel. They should be very difficult to turn by hand.

The car does not need to be on, but you should if you can. If not then turn the car on let it idle for a minute. Then don't touch the brakes until your ready. You'll still have vacuum for awhile after you turn the car off.

If you have to, do it one wheel at a time.

Now I understand your getting flow, but that's not the same as pressure. It doesn't take much to get flow, you need to test if your getting any pressure at all.



This is unlikely, but it's a simple thing to try.
Remove the master cylinder reservoir caps, then try the brakes. Only once or twice, don't pump them. Replace the caps.

On occasion a vacuum will form over the fluid in the reservoir, this makes it difficult or impossible to build brake pressure because the fluid is literally pulled up and out of the master cylinder.

Also, check the booster output rod relation to the master cylinder. If the rod is adjusted too long it will not allow the master cylinder piston to come back far enough to open the replenishing ports. Again you would not be able to build adequate pressure.

 

I have a 91 and have rebuilt every piece of the brakes on it at different times.

IMHO you have air in the ABS or trapped in the system somewhere.

I don't use pressure to bleed mine.
I use a BIG syringe with a clear tube connecting it to the caliper bleed valve.
It sucks the fluid from the master cylinder thru the system.
(thru the ABS unit also)
The master cylinder has to be kept filled when you do this or you will suck more air into the system.

The syringe is used to suck the fluid out. Empty the syringe when it is full into a can or bottle.
When no more air bubbles come out, move to the next caliper.
It takes a LOT of fluid to get all the air moved out of the system sometimes. Air DOES NOT move as fast as the fluid does when you do this. It hangs at bends in the tubing, etc.

Anyway this is what has worked many times for me and thought you may want to give it a try.

It's cheap, easy and you can do it by yourself, just keep the master cylinder from running dry during the process.

You can probably get a LARGE syringe from a veternarian.
You don't need the needle part, just the syringe.
Get the clear tubing at a hardware store for about a dollar.

Some may say go to the caliper the fartherest from the master cylinder first but I have never done that. Just started at whichever one I felt like first.

I've used this procedure on two of my C4 Vettes and it has always worked.

BTW, DO USE Speeder Bleeders.
They make it a LOT easier to bleed the brakes without help and without sucking air back into the system.
About 6 or 7 dollars apiece. Get'em.

Good luck with it.

Another BTW: The cap stays off the master cylinder during this whole operation. You need to be CLOSELY checking it anyway to make SURE you don't suck it dry.

 

I learned a little trick from a garage on how to isolate the calipers. Find the rubber hoses headed to the calipers and clamp them closed with soft jawed vice grips(use fuel hose in the jaws) or something similar. If possible - I would do all 4 at the same time (may have to borrow from the neighbors). Press the brake pedal. If it is hard then one of the calipers is faulty. You could then systematicaly remove the clamps one at a time to determine which one.

 

that will at least let you know if the problem is in one of the calipers if it still goes to the floor you know the calipers aren't the problem then look at the ABS, booster or master. I've used this technique many times and it lets you know which corner you have a problem at.

 

UPDATE

I clamped off the hose to the RF caliper and I got pedal. That clamp trick is pretty cool. I am guessing that means the caliper is toast.

Assuming the caliper is dead I am on my way to the store to get one ordered.

 

UPDATE

I got the new/rebuilt caliper and installed it (and one stripped wheel stud I found), bled the brakes and I still have no pedal. I drove the car around the block while pumping the pedal a bit (0 - 20 - 0 or so) to make sure eveything was "pumped up".

What else is left to check? Could the hose be hosed? That corner is still very hard to bleed compared to the others. There is flow from the bleeder but there is also much resistance.

I plan to have another go at bleeding when the rain stops hopefully later today. Maybe there is still a stubborn bubble still there.

Any ideas?

 

Most definately it can be the hose. The inside will split and clog the hole. I have read about many instances of this happening. If you changed the caliper - that is all that is left.

I have the steel braided brake lines and I love them.

 

Thanks for the confirmation.

I am in the process of buying a "nearly-new" set of Earl's braided Hose from a forum member and hoping it solves the problem.

Thanks