proportioning (Combination) valve

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dedub

Greasemonkey
Aug 18, 2008
209
12
18
N.C. Fort Bragg
Here is the history of my 80 El Camino.
It sat for 5 months while I was deployed with the old calipers disconnected. That was an unfinished project I couldn't get done before leaving. When I got back I replaced the calipers with Wilwood and brand new rotors. After exhaustively bleeding the brakes they still didn't feel right. I swapped the master cylinder for a brand new one and was sure to bench bleed it before installation. 2 to 3 more rounds of bleeding and they still are squishy. A friend mentioned the proportioning valve and "resetting" it. That's a new one. Does anyone have an idea on how to check it or reset it?

Thanks
 

megaladon6

Comic Book Super Hero
May 29, 2006
4,006
15
0
Danbury, CT
there's a small pin on the front of the prop valve. IIRC you pull the pin out slightly, then bleed the brakes.
BTW are you gravity bleeding them, or pressure bleeding with an assistant?
 

khan0165

Royal Smart Person
Jul 14, 2008
1,617
15
38
Ontario, Canada
I'm not sure how a proportioning valve is "reset", but it can fade. The one in my GP started to fade, so an aftermarket one was installed.

You can buy adjustable ones and replace your old one. Mine was installed in addtion to the original, but only on the rear brakes. So as the rear brakes start to fade, I just dial up the pressure on my additonal one.

here's a picture of it...
DSC02896.jpg


you can buy others that will install to both front & back, and are adjustable.
 

19cutlass79

Greasemonkey
Mar 7, 2010
233
0
16
on my 79' lemans wagon I didn't have a pin but a button (rubber) in the front that I had to keep depressed while bleeding the rears since they were totally dry cause I swapped rear ends, maybe there are two kinds of prop valves?

wade
 

megaladon6

Comic Book Super Hero
May 29, 2006
4,006
15
0
Danbury, CT
or i'm remembering it backwards
 

dedub

Greasemonkey
Aug 18, 2008
209
12
18
N.C. Fort Bragg
megaladon6 said:
there's a small pin on the front of the prop valve. IIRC you pull the pin out slightly, then bleed the brakes.
BTW are you gravity bleeding them, or pressure bleeding with an assistant?
To answer that question I'm pressure bleeding. Funny thing is I just now pulled out my Chiltons and here's what I read.. "On cars with front disk brakes, it will be necessary to hold in the metering valve pin during the bleeding process." Holy S#@^. I never knew that. Been bleeding brakes since 1985 on Chevy's and I've never done it right. Hopefully that will fix my issue and I'll be GTG.
 

79loserbluebu

G-Body Guru
May 9, 2009
960
20
18
Illinois
I'm thinking this may be the cause for my soft pedal as well. If you don't push that button in, can you bleed the rears like normal and fluid will come out still?
 

19cutlass79

Greasemonkey
Mar 7, 2010
233
0
16
79loserbluebu said:
I'm thinking this may be the cause for my soft pedal as well. If you don't push that button in, can you bleed the rears like normal and fluid will come out still?

Honestly I never tested the theory, from what I read there was a alot of people that had this problem it's some kind of failsafe so you don't lose all your fluid if there is a break somewhere, supposedly when there is no pressure or too much air in the line it closes, so when I did my rear end swap I didn't do any trial an error right off the go I jammed socket and bolt the socket was not long enough by itself between the chassis and the prop valve button to fully depress it and gravity bled the rears and when it was all good tightened the bleed screws removed the "wedge" and I was done. If anyone actually knows what that button is for please correct my post! :D

wade
 

pontiacgp

blank
Mar 31, 2006
29,270
20,391
113
Kitchener, Ontario
I found that if the valve needed to be reset driving backwards and tromping on the brakes you'd hear the valve click and it'd be reset...it sometimes took a few tries...I use speed bleeders and was able to bleed the rear brakes before resetting the valve.
 

khan0165

Royal Smart Person
Jul 14, 2008
1,617
15
38
Ontario, Canada
wow, I never knew any of this...
I've only ever used the bleeder screws and got someone to press the brakes.

how does this valve work? How does it effect bleeding?
 
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