'65 power brakes

[Jeremy Hedges]

I have a '65 with PB w/original master cylinder. I have just finished a frame-off on this and I am working out the bugs. After the car warms up or builds up vacuum, the brakes seem to get tight, it is like the parking brake is on. I removed the master cylinder to see about adjusting the rod from the booster (like the shop manual talks a bout) but the rod coming out of my booster is not adjustable, is this the correct rod? What could be the problem?

Jeremy Hedges
#31711

[Jeremy Hedges]

Re: '65 power brakes

That first post of my brake question was wrong, after I thought about it, I went out and jacked up the front end and there is no drag on the front wheels, but there is drag on the rear, I adjusted the parking brake star in the wheels to provide the least amount of tension and the cable from the handle is not tight, but I still have drag on the rear wheels. In '65 there was not a proportioning valve. What could be the problem?

Jeremy Hedges
#31711

[Mike M.]

Re: '65 power brakes

i assume you replaced the rear rubber hoses . if not , do so as that is easier than tearing the rear emergency brakes apart, which is the next diagnostic venture if the rubber hoses are new or replaced..good luck, mike

[William C.]

Re: '65 power brakes

use the bleeder valve on the rear calipers to release any pressure, then check for drag. Some (light) drag is normal on the rear and is attrituble to the "machinery" hooked to the rear wheels that must be turned to make the wheels rotate. If the release of pressure via the bleeders improves the drag situation, then you need to look for an obstruction in the line, or a problem between the master cyl and booster. BTW the Corvette must have an adjustable pushrod to make sure the piston in the master cyl is fully retracted. This can cause drag.

[Joe L.]

Re: '65 power brakes

Jeremy-----

I agree with Mike and Bill. Also, one other point of clarification: VERY few Corvettes ever had a brake system PROPORTIONING VALVE. The only ones that did were 66-68 with J-56 HD brakes (this was an adustable proportioning valve) and 78-82 (this is a COMBINATION valve which has a fixed proportioning ratio).

[Geoff C.]

[William C.]

Re: '65 power brakes

Not talking front here, I was referring to the rear rod only.

[John C.]

Re: '65 power brakes

I had this same problem with a Mazda. The hose from the intake manifold to the PB booster had an internal check valve and if this hose was installed backward you got the "parking brake on" effect! However, I believe the 65 booster's check valve is the white (or brownish) plastic device the vacuum hose connects to on the booster so it may be impossible for this to be installed backward.

[Joe L.]

Re: '65 power brakes

John------

Only an absolute klutz could get the valve installed backward on a Corvette. But, then..........., who knows?