67 Corvette Brake Issue

[72-SS-L48]

Good Evening,

I'm working on a 67 Corvette. A little background, a few years ago the previous owner did brakes on the car. Stainless steel lines that still look good, the rotors look fresh, calipers aren't leaking, and hoses are still pliable. The issue is the brake pedal goes straight to the floor and the car barely stops. Today I pulled off the wheels and attempted to bleed the system. Believe it or not very little to no fluid came out of the bleeders. And yes the master is full of fluid. The master is not original, nor leaking but it does look rusty and old.

Right now I'm thinking there is a clog stemming from the master and I'm ready to change the it. Before doing so, can anyone shoot any other ideas to look into to?

Also could it be the distribution block located directly under the master? This is a standard brakes car. Not PB.

Thanks,
Dave

[VintageMusclecar]

Make sure the master cylinder pushrod is correctly adjusted. Try bench bleeding the master cylinder as well.

Eric

[72-SS-L48]

[ QUOTE ]
Make sure the master cylinder pushrod is correctly adjusted. Try bench bleeding the master cylinder as well.

Eric

[/ QUOTE ]

The master does not have a bleeder. How do you go about bench bleeding it?

Thanks Eric!

-Dave

[galveston]

I had a 67 with the same issue, turns out push rod length was to long, I unbolted the master and pulled it away from the firewall half an inch leaving nuts on the studs then bleed system and had correct pressure.
Turns out length of rod was not letting the piston return back far enough to activate brakes correctly.I changed the push rod then I had great brakes.

[VintageMusclecar]

If the master sits level in the car you can do it while it's still on the car, otherwise you'll need to remove it and carefully clamp it level in a bench vise. You'll need two plastic adapters with the appropriate thread size for the master cylinder and two sections of line to run from the adapters back into the reservoir. Most auto parts stores have a universal kit to do this. If you have any scrap sections of steel brake line handy that have the correct fittings to match the master cylinder that will work as well, just cut them to length and bend the lines in a semi-circle so that when they're attached the line routes back into the master cylinder wells. Make sure the ends of the tubes (or lines) are at least 1/2 way down into the wells so they stay submerged.

Fill the reservoirs with fluid and slowly stroke the piston in & out the full length of its travel. You will see bubbles coming from the submerged ends of the lines as the air inside the master cylinder is purged. When you don't see anymore bubbles the master cylinder is bled.

Alternately you can cap off the discharge ports (using plastic fittings like the ones that come on most new/rebuilt master cylinders) and use the same basic process as described above until you don't see any more bubbles coming from the feed holes in the reservoirs. I prefer the old-fashioned way (with the tubes/lines) myself. Below is a youtube video showing how to do it with the plugs instead.

https://www.youtube.com/watch?v=_VMXC2xsy2s

[napa68]

Dave,
As mentioned, bench bleed the master before anything else. This will also address the volume issue as far as the master is concerned. I did a 67 for my Father a couple of years ago and the car had a HUGE improvemnt by replacing the proportioning valve (under the master). I chased that problem for years. Mind you, I had a volume problem only to the rear. In addition to all of that, try vacuum bleeding instead of pressure bleeding. You may experience better results.

Best of Luck!

Tim

[72-SS-L48]

Hi Guys,

Thanks for the replies. I plan to tackle the brakes tomorrow so I will let you know what I find.

All the best,
Dave

[72-SS-L48]

Update -

Today I replaced the master cylinder and distribution block. Then I bleed the calipers and now I have pressure in the pedal. I'll road test it tomorrow.

Also I did bench bleed the new master before installing it.

Thanks for all the help!
-Dave