65 brake fluid change

[Dave B.]

I feel REALLY feel dumb asking this question but I'm at wits end. I had no idea when the brake fluid was change in a '65 I bought last year (my 1st C2). I checked the MC and the fluid looked discolored so I decided to change the fluid using a Mitvac unit that I've used on other cars numerous times.

I changed the fluid in the MC and proceed to draw fluid from a rear caliper. All seemed normal at first until I checked the MC and saw the fluid level was not dropping. It looks like somehow I evacuated the line of fluid and it filled with air. So I closed up the MC and tried the old method of pumping the brake with the bleeder screw open to start evacuating the air and bleed the line. I got no pressure coming thru the brake line when the pedal was moved - no evidence of bubbles in the fluid on the container let alone any fluid coming thru the line. It's acting like the MC is closed off from the brake lines yet the brakes were fine before I decided to do this job!

Also, I see there are two bleeder fittings on the read caliper. If I ever do get this bleeding operation working, is there a recommended sequence as to which fitting to bleed first?

Thanks for any help out there.

Dave Brown

[Chuck S.]

Re: 65 brake fluid change

I feel REALLY feel dumb asking this question but I'm at wits end. I had no idea when the brake fluid was change in a '65 I bought last year (my 1st C2). I checked the MC and the fluid looked discolored so I decided to change the fluid using a Mitvac unit that I've used on other cars numerous times.

I changed the fluid in the MC and proceed to draw fluid from a rear caliper. All seemed normal at first until I checked the MC and saw the fluid level was not dropping. It looks like somehow I evacuated the line of fluid and it filled with air. So I closed up the MC and tried the old method of pumping the brake with the bleeder screw open to start evacuating the air and bleed the line. I got no pressure coming thru the brake line when the pedal was moved - no evidence of bubbles in the fluid on the container let alone any fluid coming thru the line. It's acting like the MC is closed off from the brake lines yet the brakes were fine before I decided to do this job!

Also, I see there are two bleeder fittings on the read caliper. If I ever do get this bleeding operation working, is there a recommended sequence as to which fitting to bleed first?...

You probably haven't ACTUALLY bled ANY fluid out of the system, but you will really need to bleed the brakes now. When the caliper bleed fitting is loosened, and vacuum applied to the fitting with a pump, air is drawn in around the threads of the bleed fitting. This is the weakness of the vacuum bleeding method. I finally gave up on vaccum bleeding in frustration while trying to bleed my C4.

The old fashioned method with a partner pumping and you bleeding actually works better, but C2/C3 Corvette brake systems can be challenging for this method. The pressure bleeding method is the best and what was used at the factory. A pressure bleeder applies fluid pressure to the MC through a sealing cover. Fluid with entrapped air is expelled at the caliper bleeder valves. Always start with the longest tube, or right rear...then left rear, right front, left front.

[Martin N.]

Re: 65 brake fluid change

I feel REALLY feel dumb asking this question but I'm at wits end. I had no idea when the brake fluid was change in a '65 I bought last year (my 1st C2). I checked the MC and the fluid looked discolored so I decided to change the fluid using a Mitvac unit that I've used on other cars numerous times.

I changed the fluid in the MC and proceed to draw fluid from a rear caliper. All seemed normal at first until I checked the MC and saw the fluid level was not dropping. It looks like somehow I evacuated the line of fluid and it filled with air. So I closed up the MC and tried the old method of pumping the brake with the bleeder screw open to start evacuating the air and bleed the line. I got no pressure coming thru the brake line when the pedal was moved - no evidence of bubbles in the fluid on the container let alone any fluid coming thru the line. It's acting like the MC is closed off from the brake lines yet the brakes were fine before I decided to do this job!

Also, I see there are two bleeder fittings on the read caliper. If I ever do get this bleeding operation working, is there a recommended sequence as to which fitting to bleed first?

Thanks for any help out there.

Dave Brown

DAVE-

Perhaps your bleeder screw is plugged / contaminated, try removing the bleeder srew entirely and see if you get fluid coming out.

Normally the bleeding process starts with the FURTHEST (R.R. Outer)bleeder from the master cylinder to the Closest (L.F.)

Marty

[Paul J.]

Re: 65 brake fluid change

Dave:

If you're sure that the line is empty, you obviously have a leak, probably at the master cylinder. This is confirmed by the fact that you can't get any pressure to pump fluid back into the line. I would assume that the seals are gone, but I think that you would still see the fluid level drop unless it's leaking from the back. If you take the MC off there should be some evidence of leakage on the back. Otherwise, it could be a fitting at the MC or the block (I don't think your car has a proportioning valve). I work on and restore old cars and I've never seen a brake line with a hole in it, but I guess that could be a possibility too. While there could be a blockage, it would also be low on my list.

If you decide that it's the MC, the rebuild kits are cheap and easy to install. I hope this helps.

Paul