Brake Question-68 Corvette

[Kurt B.]

Gentlemen:
Need your collective wisdom please.
68 coupe with power brakes.
Symptom: Pedal goes to within 1/2 inch of floor board before vehicle comes to complete stop.
Professionally rebuilt power brake booster and master cylinder(bore was stainless steel sleeved).
Fluid level (Dot 3)in master cylinder is perfectly clean and clear and remains constant so I assume there are no leaks. No leaks apparant at wheel calipers (stainless steel sleeved) and no fluid on ground.
Car is not driven (still in restoration process) and system was completely rebuilt within last 12 months and driven only back and forth in driveway and brakes were perfect until today. Pumping up pedal changes nothing so I am assuming I do not have air in the lines.
Did my master cylinder go bad while car was sitting in garage?
Any input or suggestions welcomed.
Thank you in advance,

[Rich G.]

Re: Brake Question-68 Corvette

I had the same symptoms on my 68 PB car. Even though there were no leaks evident, the MC was bad. Speculation was it was leaking between front and rear "chambers". There was no brake warning light. So, since I had a correctly dated one waiting for rebuild, I had it done and it fixed the problem. The old one was not that old, several years but only a few thousand miles. I was not sure it was the MC, but a mechanic I trust thought so and when I posted the question here, that's the advice I got, too. When mine went bad it did it "overnight" in the sense that one day, I noticed it and it had been ok the last time I drove it. This car gets driven at least once every 2 weeks.

Good Luck

Rich Giannotti

[Ed Jennings]

Re: Brake Question-68 Corvette

Check for air in rear calipers prior to doing anything else. They are hard to bleed properly and very prone to air pumping if the rotors have excessive runout. Just a hunch, but check them first.

[Kurt B.]

Re: Brake Question-68 Corvette

Thanks for the input.
Sure hope it is not the Master cylinder as it is the correct date code for the car and was rebuilt profesionally within the last 12 months. Hate to have it done again but can't replace it as I want to keep the correct part number and date code. Oh well,,,

[Ed Jennings]

Re: Brake Question-68 Corvette

If you have a pressure bleeder, or can borrow one, use it to bleed all 4 brakes. That way, you can be certain that all the air is out of the system. You can buy a pressure bleeder these days for around $60, and it is an excellent investment if you do much brake work.

[Jim T.]

Re: Brake Question-68 Corvette

Kurt since your have no road miles on the 68, just movement in the driveway, and everything is rebuilt, I would do a complete bleeding of the calipers and start with bleeding the master cylinder bleeder valves.