The largest community of 1978-1988 General Motors G-Body cars. Chevrolet Malibu, El Camino, Monte Carlo; Oldsmobile Cutlass, 442, Hurst/Olds; Buick Regal, Century, T-Type, Grand National; Pontiac Grand Am, Grand Prix, LeMans, Bonneville; GMC Caballero

proportioning (Combination) valve

Stuff like brakes, frame, springs/shocks, tranny's, etc. etc.
User avatar
dedub
G Body Guru
 
Posts: 208
Joined: Mon Aug 18, 2008 3:46 pm
Location: N.C. Fort Bragg

proportioning (Combination) valve

Postby dedub on Mon Nov 22, 2010 8:50 pm

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
Darrin
My Site http://www.networxcomputer.net/Elky/elky.html
My Speed Shop http://www.polkcountyspeed.com/6.html
My time slips http://www.networxcomputer.net/Time-Slips.html

1980 True SS El Camino
385 Stroker 460 HP 455 Tq.
Ceramic Coated Headers
Mark VIII Electric Fan
Turbo 350 BUILT!
3.42 8.5" posi out of a GN
Custom Cross member with 3" Exhaust
F41 package
Frame off, new bushing, sway-bar, tie rods, bushing, brakes ect..
West Coast Suspension Tubular control arms
Custom interior, buckets, B&M floor shifter, gauges
Methanol Injection

User avatar
megaladon6
Royal Smart Person
 
Posts: 4213
Joined: Mon May 29, 2006 7:19 pm
Location: Danbury, CT

Re: proportioning (Combination) valve

Postby megaladon6 on Mon Nov 22, 2010 8:58 pm

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?
87 monte ss t-top 200-4r trans. 383ci 4-bolt, 9.7: hypereutectics, forged rods, vortec heads, xe274 cam, Q-Jet-home modified, Evans NPG+ coolant

User avatar
khan0165
Royal Smart Person
 
Posts: 1697
Joined: Mon Jul 14, 2008 7:06 pm
Location: Ottawa, Ontario, Canada

Re: proportioning (Combination) valve

Postby khan0165 on Mon Nov 22, 2010 9:02 pm

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...
Image

you can buy others that will install to both front & back, and are adjustable.
83 GP, 350, 700r4, 8.5 10bolt, 3.42 gears, 16" IROC wheels, 13.6sec @ 103mph (on tires), 12.6sec @ 105mph (on slicks)

User avatar
19cutlass79
G Body Guru
 
Posts: 261
Joined: Sun Mar 07, 2010 3:29 am

Re: proportioning (Combination) valve

Postby 19cutlass79 on Mon Nov 22, 2010 9:03 pm

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
1979 Pontiac lemans wagon
1979 oldsmobile cutlass (sold)
Ratty wagon build thread:http://gbodyforum.com/viewtopic.php?f=38&t=22701

User avatar
megaladon6
Royal Smart Person
 
Posts: 4213
Joined: Mon May 29, 2006 7:19 pm
Location: Danbury, CT

Re: proportioning (Combination) valve

Postby megaladon6 on Mon Nov 22, 2010 9:12 pm

or i'm remembering it backwards
87 monte ss t-top 200-4r trans. 383ci 4-bolt, 9.7: hypereutectics, forged rods, vortec heads, xe274 cam, Q-Jet-home modified, Evans NPG+ coolant

User avatar
dedub
G Body Guru
 
Posts: 208
Joined: Mon Aug 18, 2008 3:46 pm
Location: N.C. Fort Bragg

Re: proportioning (Combination) valve

Postby dedub on Mon Nov 22, 2010 9:14 pm

megaladon6 wrote: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.
Darrin
My Site http://www.networxcomputer.net/Elky/elky.html
My Speed Shop http://www.polkcountyspeed.com/6.html
My time slips http://www.networxcomputer.net/Time-Slips.html

1980 True SS El Camino
385 Stroker 460 HP 455 Tq.
Ceramic Coated Headers
Mark VIII Electric Fan
Turbo 350 BUILT!
3.42 8.5" posi out of a GN
Custom Cross member with 3" Exhaust
F41 package
Frame off, new bushing, sway-bar, tie rods, bushing, brakes ect..
West Coast Suspension Tubular control arms
Custom interior, buckets, B&M floor shifter, gauges
Methanol Injection

User avatar
79loserbluebu
Royal Smart Person
 
Posts: 1030
Joined: Sat May 09, 2009 9:17 pm
Location: Illinois

Re: proportioning (Combination) valve

Postby 79loserbluebu on Mon Nov 22, 2010 9:20 pm

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?
79' Malibu
LQ4/4L60E/8.5
11 second full weight street car

User avatar
19cutlass79
G Body Guru
 
Posts: 261
Joined: Sun Mar 07, 2010 3:29 am

Re: proportioning (Combination) valve

Postby 19cutlass79 on Mon Nov 22, 2010 9:38 pm

79loserbluebu wrote: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
1979 Pontiac lemans wagon
1979 oldsmobile cutlass (sold)
Ratty wagon build thread:http://gbodyforum.com/viewtopic.php?f=38&t=22701

User avatar
pontiacgp
Royal Smart Person
 
Posts: 12419
Joined: Fri Mar 31, 2006 2:30 pm

Re: proportioning (Combination) valve

Postby pontiacgp on Mon Nov 22, 2010 9:41 pm

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.
Image

User avatar
khan0165
Royal Smart Person
 
Posts: 1697
Joined: Mon Jul 14, 2008 7:06 pm
Location: Ottawa, Ontario, Canada

Re: proportioning (Combination) valve

Postby khan0165 on Mon Nov 22, 2010 9:49 pm

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?
83 GP, 350, 700r4, 8.5 10bolt, 3.42 gears, 16" IROC wheels, 13.6sec @ 103mph (on tires), 12.6sec @ 105mph (on slicks)

User avatar
pontiacgp
Royal Smart Person
 
Posts: 12419
Joined: Fri Mar 31, 2006 2:30 pm

Re: proportioning (Combination) valve

Postby pontiacgp on Mon Nov 22, 2010 9:56 pm

you loosen it 1/4 turn and it has a check ball in it so it releases the brake fluid and shut off when the pressure is released..I gravity bleed while nursing a beer then finish it up with the speed bleeders. I bought the first set from a speed shop a few years ago then they were just new up here so they cost me close to $40 for the 4 but now they are at the local parts store on the help rack for about $24 for 4


Image
Image

User avatar
dedub
G Body Guru
 
Posts: 208
Joined: Mon Aug 18, 2008 3:46 pm
Location: N.C. Fort Bragg

Re: proportioning (Combination) valve

Postby dedub on Thu Nov 25, 2010 10:09 am

After reading all the posts I have a theory on what happened.
My car sat for 5 months without front calipers, the proportioning valve eventually moved so all the fluid was redirected toward the rear. Thinking back I really didn't notice a *whole* lot of pressure on the front calipers while pressure bleeding them. That's probably why they feel real squishy while I'm driving too, only the rears are being engaged. Some how the valve is probably stuck and not letting most of the fluid be directed toward the front. I'll try a few of the recommendations posted above or just get a new OEM and be done with it. Thanks for all your help.
Darrin
My Site http://www.networxcomputer.net/Elky/elky.html
My Speed Shop http://www.polkcountyspeed.com/6.html
My time slips http://www.networxcomputer.net/Time-Slips.html

1980 True SS El Camino
385 Stroker 460 HP 455 Tq.
Ceramic Coated Headers
Mark VIII Electric Fan
Turbo 350 BUILT!
3.42 8.5" posi out of a GN
Custom Cross member with 3" Exhaust
F41 package
Frame off, new bushing, sway-bar, tie rods, bushing, brakes ect..
West Coast Suspension Tubular control arms
Custom interior, buckets, B&M floor shifter, gauges
Methanol Injection

User avatar
79loserbluebu
Royal Smart Person
 
Posts: 1030
Joined: Sat May 09, 2009 9:17 pm
Location: Illinois

Re: proportioning (Combination) valve

Postby 79loserbluebu on Fri Nov 26, 2010 10:51 pm

Let us know what you come up with!
79' Malibu
LQ4/4L60E/8.5
11 second full weight street car


Return to Chassis / Drivetrain / Suspension / Wheels

Who is online

Users browsing this forum: No registered users