1967 bleeding brakes on an entire new brake system

[Dave K.]

Re: 1967 bleeding brakes on an entire new brake system

I bled the master cylinder by removing front and rear brake lines and ran a clear tube front the front brake line back to the reservoir ( brake fluid in it) and another clear tube from the rear brake line back up to the reservoir (brake fluid in it). I saw the fluid circulate thru the tubes as my son pumped the brakes numerous times. I then went to the right rear and had my sone pump 100 times with NO fluid. Same level of brake fluid remained in the resevoir. ONE FRUSTRATION AFTER THE NEXT.?????

[Bob H.]

Re: 1967 bleeding brakes on an entire new brake system

Not knowing your level of expertise makes some suggestions probably sound stupid but here goes, are all bleeders closed when he is pumping the brakes and if so are you opening one at a time and closing it before he lets up on the pedal? That fluid you saw in the clear tubes can only replace the air currently in the lines and opening one bleeder at a time after pumping the brakes and holding the pedal down until you close the bleeder and repeat. You will not get any pedal right away

[Dave K.]

Re: 1967 bleeding brakes on an entire new brake system

I connect one end of my clear hose to the bleeder screw and the other end sits in a jar that is 1/2 full of brake fluid. I open up the bleeder screw 3/4 of a turn and then have my son slowly pump the brakes. The end of the hose in the jar shows brake fluid leaving the hose upon pushing the pedal and entering back into the hose upon releasing brake pedal. So he is not drawing air back into the line that is why it is in the jar of brake fluid. As he continues to slowly pump I'm waiting for the brake fluid to come out of the bleeder screw.....but nothing ever comes out and the fluid in the master cylinder stays at the same level.

[Leif A.]

Re: 1967 bleeding brakes on an entire new brake system

I connect one end of my clear hose to the bleeder screw and the other end sits in a jar that is 1/2 full of brake fluid. I open up the bleeder screw 3/4 of a turn and then have my son slowly pump the brakes. The end of the hose in the jar shows brake fluid leaving the hose upon pushing the pedal and entering back into the hose upon releasing brake pedal. So he is not drawing air back into the line that is why it is in the jar of brake fluid. As he continues to slowly pump I'm waiting for the brake fluid to come out of the bleeder screw.....but nothing ever comes out and the fluid in the master cylinder stays at the same level.

Wrong!!! Have your son pump the brake pedal three or four times to get a good hard pedal and then have him hold the pedal position. THEN unscrew the bleeder screw and the brake pedal will go to the floor. Have him hold the pedal to the floor while you re-tighten the bleeder screw. Repeat this process until you have a solid stream of brake fluid exiting the bleeder screw. Move on to the next bleeder and repeat process.

[Michael S.]

Re: 1967 bleeding brakes on an entire new brake system

and there is your problem. you say you open up the bleeder "then" have your son pump the pedal. then you say the fluid "draws" back into the hose when he releases the pedal. then you say no fluid is coming out at all? wtf? when you say your waiting for fluid to come out of the bleeder screw which bleeder are you talking about? the master or the wheel cylinder or caliper?
one, close "all" bleeders. two, have son pump brakes up 5 times then hold pedal down on last push. three, you open master bleeder screw then close, then have son release pedal. repeat until you have fluid coming out of master bleeder screw. then go to the right rear wheel and repeat. or just open right rear wheel and push brake pedal one or two times then let it gravity bleed. your opening the bleeder "before" there is pressure. you have to open the bleeder "after" your son pumps up the brakes and close "before" he releases brake pedal.

[Michael S.]

Re: 1967 bleeding brakes on an entire new brake system

@leif,
dang, if some one can not follow all these instructions. hire a mechanic. you got your post in just before mine. mike

[Joe R.]

Re: 1967 bleeding brakes on an entire new brake system

Wrong!!! Have your son pump the brake pedal three or four times to get a good hard pedal and then have him hold the pedal position. THEN unscrew the bleeder screw and the brake pedal will go to the floor. Have him hold the pedal to the floor while you re-tighten the bleeder screw. Repeat this process until you have a solid stream of brake fluid exiting the bleeder screw. Move on to the next bleeder and repeat process.

Two quick comments:

1) When using the "two-person" method, I have always used the following sequence. Start with the driver-front wheel, then the passenger-front wheel, then the driver-rear wheel, and finally the passenger-rear wheel:

a) Attach hose to bleeder valve
b) Open the bleeder valve about 1/2 turn
c) Have your assistant slowly push the pedal to the floor and hold it there
d) Close the bleeder valve to prevent air/fluid from being sucked back up the hose
e) Have your assistant release the brake pedal to draw more fluid in from the master cylinder resevoir
f) Repeat steps a) to e) as needed until no air bubbles come out the bleeder hose. And, BE SURE TO REFILL the master cylinder before it runs dry.


2) After using this method with great success on about 50 different (non-Corvette) cars over 50 years, I used it on my '67 Corvette after rebuilding the entire brake system including the master cylinder. While I was able to get some degree of pedal, the pedal was squishy, indicating that there was still some residual air in the system

To get that last bit of air out, I tried pressure bleeding, vacuum bleeding, and gravity bleeding (each for the first time in my life), but still had a squishy pedal. Finally, based on advice from others on this board, I took the master cylinder off the car and did the "bench bleeding" procedure on the master cylinder. That fixed the problem completely.

My theory is that when you start with a new, dry master cylinder on a C2, a small amount of air gets trapped in the very tip of the cylinder, and does not get pushed out by any of the other bleeding procedures I had tried. This is a particular risk for a C2 with power brakes, since the nose of the master cylinder is tilted upward more than with non-power brakes.

Note that in theory, "bench bleeding" can be performed with the master cylinder installed on the firewall. The key is to make sure that the piston is being pushed 100% of the way in, until it gets stopped by the end of the cylinder. Simply pushing the brake pedal to the floor may not accomplish this.

To get around that problem, you can temporarily adjust the pushrod so that the pedal bottoms out before it hits the floor. Or, you can remove the pushrod and used a large Philips screwdriver to manually press the piston all the way in until it stops.