When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 78 that I replaced the entire braking system. There seems to be very little fluid going to the back brakes. Do I need to center the proportioning valve and if so how?
I was advised to "pop" the brake pedal with my foot several times to center the valve.
(My '68 has a distribution valve to redirect fluid if the front system or rear systems springs a leak).
I don't know if you have a true proportioning valve or a distribution valve.
My valve was stuck/gummed up so I had only front brakes...I had to dissassemble and clean and recenter it.
This is the switch that turns on the dash warning light when the brake system is failing
The small piston in the middle with 2 o-rings on it is the centering valve that gets pushed to one end of the valve body(block) when the brakes fail...it is the part that needs re-centering.
Like I said...I am not sure if your '78 has the same style valve.
Do I need to center the proportioning valve and if so how?
Yes!
I just did this about two years ago but can't remember the precise steps. However, go over to the Corvette Forum and search on "proportioning valve." Your valve has a push button with a believe rubber cover at its top. You have to get under the driver's side by the front wheel (actually, behind the front tire) and look up on the frame. You'll see it. What I can't recall is weather the button is reset under pressure or not. I have a brake bleeder that I used and it worked nicely but can't recall whether I used for the valve.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Two ways to center the valve:
#1 Stomp on the brake pedal several times.
#2 Pump up and hold the brake pressure and have a helper momentarily open a front bleeder.
If that doesn't solve the problem, pump up again and momentarily open a rear bleeder.
There is a little tool for $12 that will hold the Prop Valve piston centered when doing any brake pedal bleeding tests.
Click on my avatar look for photo album brake bleeding
GM Peterbuilt,
Good post and since I have a 78 my question regarding your #1 suggestion is is this process done with the car on or off as in running or not running??
Centering 78 proportioning valve
