C2 Trouble bleeding 66 brakes

[Rob Bilger]

Finishing the body off of my 66 roadster - not a power brake car. All new brake lines, rebuilt master, rebuilt calipers. About 10 seconds after pumping up the brakes, the pedal starts to go soft. I have bled all lines completely, 3 times now - no air. Checked all connections - none loose. I bench bled the master cylinder on the car - no air - and the pedal was as hard as a rock, when shut off at the master - master seems functional. Could there be a problem with the rebuilt calipers??????

Any help is appreciated,

Rob

[Roy B.]

Re: C2 Trouble bleeding 66 brakes

Drawing air some where, most likely the master cylinder rubber inner cups or calipers O ring .

[Allan J. Wicklund]

Re: C2 Trouble bleeding 66 brakes

Try raising the back of the car while bleeding. Also tapping on the caliper before opening bleed screw sometimes helps. If you can borrow a pressure bleeder that would be a good choice. Al W.

[Rob A.]

Re: C2 Trouble bleeding 66 brakes

Rob,

Make sure all the caliper bleeder valves are completely dry. Put a small piece of paper towel around each one and then pump the brakes for several minutes. Check the paper towels at each bleeder valve. It should be easy to see if any of them are leaking. Do you have the "o" ring pistons in your calipers? Did you bleed the system manually or with a vacuum pump?

[Rob A.]

Re: C2 Trouble bleeding 66 brakes

Rob,

You can get a vacuum bleeder fairly cheap, Pep Boys, Autozone. I would try that, if you haven't already, before doing more troubleshooting. I had a similar problem after doing a frame off on my '67. The rear calipers seem to usually be the problem area.

[Richard Hayes]

Re: C2 Trouble bleeding 66 brakes

Rob,

Try to jack up the rear of the car as high as you can safely- this has worked for me-on several occasions.

Richard

[Mark Churchill]

Re: C2 Trouble bleeding 66 brakes

Rob,
Did brakes on my 66 power brake bb this year and spent 2 hours pumping and bleeding. Put new calipers and brake lines on and ended up raising the rear end a little. It just took time and adding fluid a little bit at a time. I hope this helps.

Mark

[Greg Vaka]

Re: C2 Trouble bleeding 66 brakes

A friend of mine found that he had the right caliper on the left side and visa versa. The bleed valve was on the bottom of the caliper rather than the top.

[Rob A.]

Re: C2 Trouble bleeding 66 brakes

Rob,

You can put one-way bleeder valves in. It makes it easier and quicker. When you're done, you can put the originals back in if you like.

[Wayne P.]

Re: C2 Trouble bleeding 66 brakes

Gravity bleeding always worked best for me. No air created by the pumping.

[Rob Bilger]

Re: C2 Trouble bleeding 66 brakes

WOW! Thanks for all of the responses. I will try jacking up the rear of the car. If that doesn't work, I will try gravity bleeding. I did try a vacuum pump, on my 1st try, but I was pulling air around the bleeder threads.

[Mark Milner]

Re: C2 Trouble bleeding 66 brakes

Gravity bleeding has disadvantages. It takes quite a while if you are flushing the system or if it is new. You also need the MC cap off/loose so that it flows better, which isn't good on a humid day.

Stick a catch pan under the caliper, crack the bleeder, and go do something for 5 or 10 minutes. Come back and check the MC level. If it goes empty, you have to flush the whole thing.

Repeat the process for all SIX bleed screws. You are doing all four on the rear, right? Don't mean to sound condescending, but you would be amazed at the ones who bleed only one screw on each rear.

[John H.]

Re: C2 Trouble bleeding 66 brakes

Get a Motive Products pressure bleeder - best sixty bucks I ever spent for a tool; makes it a one-person 15-minute job, takes all the grief out of bleeding stubborn Corvette brakes. Instantly obsoletes Mityvacs, Phoenix Injectors, pedal-pumping, and gravity bleeding.

[Norris W.]

Re: C2 Trouble bleeding 66 brakes

I had a shop in the 80's and did a LOT of Corvette caliper replacement. First of all, silicon fluid doesn't like a lot of pumping. You'll aerate it and lose the pedal. We started out with vacuum bleed, then followed with a few minutes of supervised gravity, and finally VERY GENTLE pedal bleed. I've seen a few that despite the best effort still get foamed some and often they'll get well overnight. It's also possible to have a bad caliper and a master cyl with an internal leak can drive you nuts.

I quit before they stareted doing the O Ring types, so don't have experience with them.

[John Lokay]

Re: C2 Trouble bleeding 66 brakes

I recently replaced the front right caliper on my '66 and used the Mytivac hand pump to bleed the system which worked well for me (the system has silicone fluid). What I did however, to prevent air from getting into the system when I opened the bleeder screw was to place gear lube around the base of the screw. I was a bit surprised how easy it was for me to bleed the system, maybe I got lucky, just make sure you continue to check the fluid level in the master. Good Luck.