brakes
Thread Starter
Racer
Joined: Feb 2005
Posts: 374
Likes: 4
From: decatur ga
brakes
I have a 76 coup automatic transmission car. I'm not getting enough fluid to the calipers to stop the car. I put my second master cylinder on today. when pumping to bleed or using the bleed machines fluid shoots out .However it seem not enough pressure. Can the brake proportioning value stop pressure?
Thanks for your help
Callahan
Thanks for your help
Callahan
Le Mans Master
Joined: Aug 2005
Posts: 6,539
Likes: 1,973
From: Temple Terrace Florida
If the rubber brake lines are old, that could be your problem. They can look great on the outside but be blocked on the inside. Have you blead both halfs of the rear calipers and blead the fronts as well? Start from the right rear, left rear, right front and finely, the left front. Jerry
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
replace all 4 rubber brake lines. the proportioning valve is not a proportioning valve. it is a piston that goes one way or the other to turn on the brake warning switch. doesn't shut off or regulate fluid flow. it needs to be reset to center. https://www.corvetteforum.com/forums...ing-valve.html but if you haven't replaced the flex lines they are a lot older than you think.
Last edited by derekderek; Apr 1, 2022 at 01:32 PM.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Early C3s had distribution blocks.
O.P. 1976 has a Proportioning Valve. In the event of a leak / loss of pressure the valve shuts off the rears and proportions the DOT3 to the fronts. And vise-versa.
It's a safety valve so you are 50% likely to have "some" brakes.
calvette 11,
I assume you are loosening the bleeder screws far enough to allow fluid out. Some of those aftermarket bleeders are finicky. And some are loose in their threaded bores.
I would stay away from the pedal. Using that will just add issues to your bleeding procedure. If the Dash Brake Warning Light is illuminated (key on) then a quick jab of the pedal will reset the switch in the Prop Valve 90% of the time.
The Proportioning Valve seldom fails mechanically (electrically yes). Really basic piece of brass with a piston & spring.
The fact that the pedal does not go to floor indicates a blockage of some sort, but where?
Kind of ironic, you just replaced all the lines last week. You need to back-track your work. You missed something somewhere.
O.P. 1976 has a Proportioning Valve. In the event of a leak / loss of pressure the valve shuts off the rears and proportions the DOT3 to the fronts. And vise-versa.
It's a safety valve so you are 50% likely to have "some" brakes.
calvette 11,
I assume you are loosening the bleeder screws far enough to allow fluid out. Some of those aftermarket bleeders are finicky. And some are loose in their threaded bores.
I would stay away from the pedal. Using that will just add issues to your bleeding procedure. If the Dash Brake Warning Light is illuminated (key on) then a quick jab of the pedal will reset the switch in the Prop Valve 90% of the time.
The Proportioning Valve seldom fails mechanically (electrically yes). Really basic piece of brass with a piston & spring.
The fact that the pedal does not go to floor indicates a blockage of some sort, but where?
Kind of ironic, you just replaced all the lines last week. You need to back-track your work. You missed something somewhere.
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Le Mans Master
Joined: Jan 2001
Posts: 6,741
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Did you replace the brake hoses? You say you replaced "lines" - did you do the hoses?
If you are not getting flow AT ALL, then disconnect the fitting at the caliper and see if you get flow. Start there and work back towards the master cylinder to find your blockage.
If you are not getting flow AT ALL, then disconnect the fitting at the caliper and see if you get flow. Start there and work back towards the master cylinder to find your blockage.