Ive read the forum posts so I am probably beating a dead since C3's are brake nightmares.

Brake pedal goes to floor. unable to pump them up. First thought is i replaced the master, system completely blead. Problem not resolved. Did a 10 mph brake check. Fronts locked up but nothing in the rear it seemed. The EMER brake is pretty weak so coinsiding with the thought of rear brakes possibly being the issue. So the thought of the calipers not reciprocating to the original positions due to a mechanical issue with EMER brake. Just want possible suggestions of where to start if anyone has delt with this before.

Oh yea..from another thread about the master cylinder push rod difference from Auto parts store...wouldn't you be able to still build pressure from pumping or is that significantly different? 90% sure the old master is original so being no difference in the end result is not reason for issue.

The brake sys is fairly new from when i purchased it. Not sure how old the rubber lines but they are in good condition. Does not leak so proportioning valve doesnt seem logical?

 

The rears can be a pain to bleed compared to other vehicles. The best thing to do is to get a vacuum pump or brake bleeder. They are inexpensive at Harbor Freight.

Also, when you bled the rears, did you bleed both the inboard and outboard parts of the caliper? C3's have two bleed screws on each rear caliper.

If the fronts are grabbing and the rear isn't then you probably have air back there still.

The parking brake is mechanical. If it is weak it needs to be adjusted. Weak rear hydraulic brakes won't have any connection with the parking brake.

 

However, you don't need anything fancy to bleed the rear brakes. First off, for how long has the fluid been in there? If it's more than a few years, I would strongly suggest that you open all four rear bleeders and let ALL of the old fluid drain out. Do the front as well. First though, run the front of the car up on some ramps to allow gravity to be your friend. Then pour some methylated spirits into the MC and let that drain through.

You can help it get through with the brake pedal, but be careful of the fluid hitting any paint. When there is nothing but clean metho coming through, then let all of that drain out and fill with new brake fluid. Putting some clear plastic hose onto the bleeders and catching it in a clean can means that you can use this to top up the MC.

Frequently check the level in the MC. If you leave it overnight, then most of the air bubbles, especially in the rear lines, will have worked their way up to the MC by the following morning. Then, just choose a wheel, any one - it doesn't matter, and put the plastic hose onto the bleeder and loosen it. At the rear, do the inner ones first.

You will then see fluid and some air bubbles filling the hose. The longer the hose the better, but the inner guards will dictate how high you can go. When the fluid is about to exit the hose, nip the bleeder up and pour the fluid into a clean container. Use this to top up the MC.

Open the bleeder again and repeat. Do this until only fluid enters the hose. Then tighten the bleeder and go on to the next wheel, any order.
This should get all of the air out of the system but if you have a friend, then at this stage you can do the "pump and release" method, but you should find very little air left in the system.

Regards from Down Under.

aussiejohn

 

vacuum pump is WAY easier than pumping the brakes until you get all the air out. You just need a cup in between the line. I always recommend starting at the farthest tire away from the master cylinder and working your way closer, also I never reuse brake fluid, its cheap enough to just buy new stuff. I would also never open up all my bleed screws at once, that just sound like a nightmare, keeping the fluid in there and just flush it out is a lot better. Biggest things with the vacuum pump is just makes sure you don't suck the master cylinder dry and you will be ok.

 

Brakes are no harder on C3's than any other car. Lots of missconceptions though..

Assuming the calipers and pads are in good shape, you mentioned you changed the master cylinder, did you bench bleed it? That's pretty much a must do or you'll push air through your lines. So, remove (or if you're good, you can do it on the car) and bleed the master cylinder itself. Then, using whatever method you prefer, vacuum, power, or manual, bleed the brakes in the following sequence:

Left rear innner, left rear outer, right rear inner, right rear outer, left front, and right front. I know this is contrary to what some like to do (start farthest from the master and work in) but it's straight out of the service manual.

Pay attention and see if 1) you get any air out of any of the lines and 2) the pedal pumps up firm at anytime. If you can get a firm pedal, you're on the right track. If not, you have other issues. Look for leaks at the calipers.

BTW, the emergency brake has nothing to do with the regular brakes on these cars. It's a competly separate system, doesn't touch the hydraulics or the calipers in anyway.

 

 

HUH? Brake pedal goes to the floor but the fronts lock up? Which is it. There is NO connection either mechanical or hydraulic between the foot brake and emergency brake.

If you've got a solid pedal and can lock up the fronts, your brakes are fine.

 

+10000000

best dang advise I have ever received! I had a similar problem to you. I bled the brakes 3 times to get the last air out. I found that using the pressure bleeder and then pushing the peddel to the floor and holding it for a few seconds I could see air going back up from the MC to the pressure bleeder bottle. Did that till I stopped seeing air and they work great now.

 

Mike Ward,

The pedal isnt solid but the fronts will lock up when pressed to the floor hard enough, but nothing in the rears in the rears really.

I am going to drain and re bleed the rears, inner and outer again. I will get back to you all. Thanks for the advice about the parking brake. That was a thought since it can be a related issue with other vehicles.

 

I have bleed brakes on a lot of different vehicles.Never had a problem till I met the Corvette.Replaced everything in the system with factory parts.Never could get it to function properly.Gave up and went the whole nine yards.wilwood calibers,mastercylinder and hydroboost.Rock hard and now it will gravity bleed.Never could get it to with new mastercylinder and rebuilt o ringed calibers.Hope you have better luck.

 

so any reason why i am getting no fluid in the rear resevoir. I pulled the brake lines off of the master and had my buddy press the pedal. I should be getting fluid squirting from both resevoirs. I have replaced the master with NAPA Master from the OEM. Same issue with both of them. Not enough Booster rod? I am buffaloed..

 

No flow even when bench bleeding? Bad M/C.

 

i had this problem... it was the proportioning valve... got a new one and fixed the problem... took the old one apart... and it was almost totally corroded on the inside.

when i flushed the system all fluid looked good... the bad gunk just stayed there...

 

Easy Mike, which model is the correct one? I was looking at those a couple days ago and it seemed confusing as to which one...

Thanks Jim

 

Ditto, I want one too.