Thread: Proportioning valve question.

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My brake pedal is sticking down on my car. It's a new set up
with a power brake booster. Drums brakes all the way around.
I haven't really had the car out yet on the road (no mufflers)
but the pedal is sticking just moving the car around. I can
pull the pedal back up with my foot, and the brakes will release.

I have this valve going to the rear brakes, but no instructions.
The brake shoes, ect. appear to be proper. There is not brake
return spring (external) I presume the booster would push the
pedal back, after the foot pressure is released.

Am I missing something ?

Daver.

If your brake pedal is sticking down, its not the booster or proportining valve. My guess would be that you have master cylinder issues. The brakes are supposed to return due to the pressure of the springs in the brakes and the fluid. If your brakes are staying down, i would guess that your brakes are catching, then its blowing past the seals in the master cylinder.

The master cylinder is new, but I guess anything is possible.
I will try it again tomorrow, I'm gonna drive it up to the
muffler shop. I bled each cylinder one pump, spooned up
the brakes a tad, and opened the valve 6 clicks.

You can see I'm getting desperate. i'll report back if it did any good.

Daver.

The pedal works fine with the engine off, as soon as
I start the engine, it sticks down.

When I had the booster off....I made sure there was a
bit of freeplay in the rod between the booster and the
master cylinder, when I re-installed.

Daver.

I just want to thank Daver and Tech1 for this information since I am about a month behind doing the same step. Daver's pictures are very helpful to me. Thanks.

Don Shillady
Retired Scientist/teen rodder

Your welcome, Don....

....does anyone know how this proportioning valve works,
or how to adjust it, and the initial setting?
What is the little red thing on top of the valve ?

Daver.

Originally posted by Daver
Your welcome, Don....

....does anyone know how this proportioning valve works,
or how to adjust it, and the initial setting?
What is the little red thing on top of the valve ?

Daver.

that little red thing looks like a residual pressure valve, that you use if your master cylender is mounted lower than your wheel cylenders and its a one way valve so the fluid cant drain back into your master cylender when you take your foot off of the brake pedal. the proportioning valve is used to balance your front brakes with your rear brakes. i always start to adj. the brake balance in the shop with the wheels off of the ground with someone pressing on the brake pedal untill you get about the same amount of drag on all 4 wheels. you are turning the knob on the proportioning valve to get this bal. when you get the front and rear brakes as close as you can, then take the car outside on some dirt and test the brakes, you wont the front brakes to lock up a little before the rear. turn the knob on the valve until you get the bal. you wont. hope this makes sense, if it dont let me know.

the residual valve might be the problem with your brake padel sticking. there is a 2 lb. valve for disc brakes and a 10 lb valve for drum brakes, see if its stamped on your valve.

Originally posted by techinspector1
I thought he meant that there was a little red thing on the prop valve that I could not see in the picture.

it might be i took it to be the residual valve. i wonder what would happen if you put the the residual valve on backwards would it hold pressure on the master cylender and cause it to lock up

Originally posted by techinspector1
If you had a 10 lb. residual valve installed backwards, it would take an effort of 10 lbs. to break it open and start the flow of fluid toward the rear drum. Most any system will develop 1,000 lbs of line pressure, so 10 lbs. isn't anything to be concerned about overcoming. Then, when you released the pedal, there would no resistance at all and the fluid pressure would relax in the line.

have to thank about this. when its right there is 10 lbs. of pressure on the brake shoes all of the time, if you turn it around then you would have 10 lbs on your master all the time. i dont know what that would do to the padel. if it was backards you probably coundnt get any brakes at all on it. i would still check to see if it was right. :

Originally posted by techinspector1
Yeah, you're right, you would have 10 on the master.

Well, at any rate, go back and read the first post. I missed it the first time I read it, but there is no return spring on the pedal (slapping myself on the forehead) DUH!!!

im drawing a blank on the return spring for the brake pedal though. im thinking the spring in the master cylender would push the padel back. could be wrong about that though. wonder where this guy is, havent heard much from him lately. i think he must have taken a power on us, like that other one did to you. i thought that, taking a power thing was funny.

Hey, keep on discussing this problem, I am learning a lot while I am dreading the installation of the full brake system. What some of you have said is covered by a diagram in the Speedway catalog but not explained as for instance the directionality of the check valve residuals or the business about the wheel cylinders being higher than the master cylinder. I also wondered why there was no spring from the very first post, but what do I know? Anyway, there should be a spring, right? My wonder has been with a 7" vacuum can between the pedal bracket and the master cylinder it seems as if my master cylinder should have some sort of bracket to support the weight of the master cylinder because the vacuum can seems kind of flimsy and the whole weight of the master is hanging out there behind the vacuum can. Anybody else have this problem or is the can firm enougn to handle pot hole vibration in a vertical direction? Meanwhile let the originator of this thread tell us about the possibility of a return spring. So far on my TCI brake pedal kit I do not see any place for such a spring.

Don Shillady
Retired Scientist/teen rodder

if you have a choice you would mount your master cylinder higher than your wheel cylinder so you can bleed your brakes. if you cant mount the master cylinder higher than the wheel cylinders, then you install a residual valve in front of the master cylender that will keep the fluid from draining back into your master cylender and lets you bleed the brakes. most master cylinders just mount to the booster, but most boosters are not flimsy so i dont know about that. you have a spring in your master cylinder and booster so i belive thats all the springs you need. ive hooked up a lot of brake and clutch padels and the reason im drawing a blank on the brake return spring i think is bacasue i didnt need one. teck 1 says he thnks you need a spring and he might be right but ill find out for sure tomorow and if im wrong then i will apologize. you shouldnt need a spring to pull the master cylinder piston back because you have the spring in the cylinder to do that, you might need to put a spring on the padel to keep it from flopping around or something like that but not to keep your brakes from locking up. i dont belive the ones that you mount in the floor has a spring on them.

Guys....I haven't bailed out....

....here's the pedal assy on the front of the booster. There is
no provision for a spring that I can see. Again....the pedal feels
fine, and returns OK with the engine off, but with the boost the
pedal goes further down, feels soggy, and won't return.

Keeping in mind....there is a return spring in the master....
there are powerful return springs in each wheel. I presume
there is some kind of a return spring inside the booster.

The way the pedal is mounted (very upright) the weight of the
pedal shouldn't be a factor.

The darned thing acts just like a "hill holder" on an old
Studebaker.....when you push it down, it stays down.

Daver.

sound like to me you have a booster problem

the only thing dif running or not running is the vac. at the booster,start the moter then cut the vac. off going to the booster and see what it does.