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Author Topic:   Brakes
Dirt Roller

Total posts: 17
posted March 12, 2005 08:18 PM  
Having problems bleeding the back brakes. It seems the portioning valve is bad.

1985 Buick Regal
Stock front brakes
Stock Master cylinder
Stock portioning valve
1986 S10 Calipers on rear w/ 1981 Eagle Rotor (ford Nine inch rear)

Basicly cannot get anything more then a small dribble out of the port for the rear brakes on the portioning valve.

Should I buy a new portioning valve? Eliminate it all together? What do all you experienced racers do?

Thanks for any help you can give.

rico 08
Dirt Forum Champ
Total posts: 1139
posted March 12, 2005 09:42 PM  
Replace the master cyl...the valve rarely goes bad...i went thru 5 rebuilt master cyl's before i got a good one.I also did away with the valve for more rear brake.

sc1 racing
Dirt Freak

Total posts: 419
posted March 13, 2005 05:52 AM  
what ever you do dont get rid off the valve. if you do you will not have any brakes. you will have to pump the heck out of them to get any pedal. i do agree it is probably in the master cylinder. either that or the rea calipers are bad.

Donnie Ross
Dirt Freak

Total posts: 264
posted March 13, 2005 05:53 AM  
check your proportioning valve to see if it is centered, a stock valve is ashuttle valve wich will push to the side with low pressure during a brake failure such as line rupture shutting off flow to that part of the system, also happens during bleeding of brakes, open the front bleeders and push the pedal part way down and have some body close bleeder while you hold it should solve problem, shop manual will have detailed info on this procedure. hope this helps

Dirt Roller

Total posts: 17
posted March 13, 2005 06:55 AM  
Rear Calipers and the Master cylinder are new.

Dirt Freak

Total posts: 402
posted March 13, 2005 07:23 PM  
your brakes will work fine without the prop valve. If they are beld properly and the calipermounts are on straight you will not have to pump the brakes. Look at any car with a dual mastercylinder-no prop valve and they work fine.

Dirt Maniac

Total posts: 167
posted March 13, 2005 07:28 PM  
have you pulled line off to the rear brakes from the master cylinder yet? I replace 1 master cylinder 1 porportioning valve both back brake clipers started to replace master cylinder again noticed nail in the line blocking of fluid to back brakes talked to previos owner he said oh yeah did that for good burn outs. was real happy to know this after replacing parts.

Dirt Freak

Total posts: 429
posted March 13, 2005 07:44 PM  
i remove my valve amd it works fine

Dirt Maniac

Total posts: 169
posted March 13, 2005 08:23 PM  
I had that problem when I put my car back together. There's a hex on the bottom, I took it out and put it back in then it worked o.k. watch out if you do it, brake fluid will run down on you.

Dirt Maniac

Total posts: 167
posted March 14, 2005 09:53 AM  
a residual valve and a porportioning valve are not same thing the porportioning valve is just a saftey feature that if front or rear brakes have a large fluid loss it blocks the off so you have brakes on the opposite. residual valve maintains a small amount of pressure on the line. wich some systems have to have to work. Woops see that was done said.

[This message has been edited by petordragon (edited March 14, 2005).]

Dirt Roller

Total posts: 24
posted March 25, 2005 09:59 AM  
You dont need brakes anyway

Keep the accelerator to the floor!!!!

Dirt Freak

Total posts: 369
posted March 25, 2005 12:08 PM  
when i changed from drum to disc on the rear of my car i took out the proportioning vavle and didn't get enough fluid to the rear brakes for them to work so i changed to a dual master cylinder set up. the stock master won't work it doesn't move enough fluid to work with rear disc set up. also check your lines that you don't have a pinched line anywhere that could be the problem too.....

oh yea brakes are for parking

Dirt Forum Racer

Total posts: 87
posted March 25, 2005 04:13 PM  
what if your master cylinder was made for 4 wheel disc brakes? IE 1988 trans am

Dirt Freak

Total posts: 369
posted March 25, 2005 07:17 PM  
if your master cylinder was made for 4 wheel disc then you will need to use the size caliper it was designed to operate usually rear disc calipers are alot smaller than the fronts from metrics that people use on the rear in conversions IE front calipers on metrics are usually about 2.5 inches across the rear on the 88 TA was somewhere about 1.5 to 1.75" alot of difference so check what size piston is in the caliper your using

drive hard or drive home

Originally posted by Mr.Kwik:
what if your master cylinder was made for 4 wheel disc brakes? IE 1988 trans am

Dirt Maniac

Total posts: 115
posted March 25, 2005 07:42 PM  
ya do not need a proportiongig valve took mine off and works a lot better

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