65 Disc Brake Problem

[Ray C.]

After one and one-half years of restoration I finally took the 1965 Roadster on its first test run. This was not a good experience!! After traveling a very short distance and a couple applications of break pedal the brake system locked up the wheels. I could not loosen up the calipers with out cracking loose the break line at the master cylinder. I had the calipers professionally rebuilt and I rebuilt the master cylinder (re-build kit from NAPA). There is approximately 1/4 inch of free play before the brake rod makes contact with the plunger in the master cylinder. The brake pedal spring returns the pedal to the 1/4-inch free play. I have re-checked the master cylinder and re-bench bleed the cylinder. After re-installing and applying pressure to the breaks system, there is considerable brake drag on all wheels. How can I determine where the problem is and how can I correct it?

Thanks for all the help!
Ray

[Larry S.]

Re: 65 Disc Brake Problem

Ray I am no expert here,But my assumption would be the master cylender.If it was just a caliper,then only one would remain locked up.But since its all of them then the only thing that controlls all of them is the master cylender.

Good luck But that would be my assumption.

[Mike M.]

Re: 65 Disc Brake Problem

take the master cyl back off, dissassemble, then make sure all the small passages from the reservoir to the cylinder are open( i use aa acetylene welding tip cleaner to punch thru all the crap that are know to block the passage. mike

[John H.]

Re: 65 Disc Brake Problem

Is it the original master cylinder? Some replacements are mis-built with drum brake residual pressure valves in the outlets - disc brake master cylinders didn't have them.

[Ray C.]

Re: 65 Disc Brake Problem

Thanks for the responses!

The master cylinder is not original to my car. The 65 came with an aftermarket master cylinder with a side outlet and a 7/8-inch bore. I purchased and rebuilt this master cylinder. The casting number is 2225032 with a one-inch bore and the correct Julian date code for my 65. The cylinder was supposed to have been removed from a 65 Corvette. (Sometimes its buyer beware) The 65-shop manual states that the rebuild process is the same as the 63-64 except that you do not install the residual pressure valve. How many small passages should I be looking for? I have located one larger one towards the rear of the reservoir (that is clear) and a very small one in the center of a v cut in the cylinder that I will check tomorrow.

Thanks for the help!

[Larry S.]

Re: 65 Disc Brake Problem

PS I forgot to say congrads on the first ride.I have done many cars (not all corvettes)and every car no matter how hard I try I always have to limp home.And have a good story to remeber the first ride with.
Congradulations Hopefully this will be the only gremlin

[Ray C.]

Re: 65 Disc Brake Problem

Thanks To All!!!

The brakes are now working. Mike was right on target!! The very small hole in the center of the master cylinder was plugged. I cleaned it and the brakes released fine!

Again!!
Thanks
Ray