Help: I need a brake proportioning valve
 

Anyone have the cast iron disc brake proportioning/combination valve for a 71 and up T/A? I believe that other GM cars of the same era used this same valve. The replacement offered by the aftermarket is brass and looks nothing like the original.

I just noticed that mine is seeping fluid from the red arrow location. Luckily I use silicone brake fluid so no paint is damaged, but it is pissing me off, as well as being a major safety issue.

I dont see anyone selling these anywhere. You can find them for the Ist Gen F-bodies but not the 2nd gens.

http://i466.photobucket.com/albums/r...brakevalve.jpg

It's been a long time since I had that style apart but isn't there an o-ring behind that?

I am pretty confident that there is a o-ring behind there. I took mine apart for curiosity to see how it worked. Should be replaceable. Might even be able to find a rebuild kit for it.

Joel

can a brass one be milled and machined then blasted to look like an original one?????
just a thought....:idea:

If I dont end up with a nice one, Im sure Franks Pontiac parts ( http://frankspontiacparts.com/ )will have a nice one, or Steve barak at pontiac heaven
http://www.pontiacheaven.org/

Both are in rust free areas..
PS ever seen the DOT #3 synthetic fluid? I use DOT 5 but just saw some with dot 3...

Steve, Billy at White Post restorations may also be able to help you. He may be able to restore that one, or provide a replacement.

http://www.mpbrakes.com/index.cfm

Give them a call and ask for Carmen. he may be able to a rebuild for you. He hooked me up with mine years back.

See if Bill Oxley will rebuild it for you.............

He can, but I need a spare to send him. I don't want to leave the brake system open to the elements while I get the valve rebuilt. He said there is an o-ring in the leaking area that is probably the culprit.

Maybe cap em in the mean time.........you already have air in the system........Bill did all my brake parts including the calipers and his work is superb...........

I have one off of a 73 Grand Prix; worked fine a year ago when I pulled it. I suspect it is the same; if you are interested, PM me.
Importsmasher

Steve
I had Bill rebuild mine when he did the master and booster.Give him a ring!

prop valve
 

I have one for you. I have a couple more I planned on sending when I got time. He's done some others for me. He does a great job. I'll find Bill's address and get them off asap since you need it soon. You can contact him and let him know your in a hurry for yours so he'll get it quicker.

Bill if your watching send me your address again in case I don't have it. [email protected]

FWIW, DOT3 and DOT4 brake fluid absorbs moisture by design. No matter how tight you think your brake system is, moisture will and does get in. With glycol based brake fluid, which is hygroscopic, the moisture is absorbed into the entire volume of fluid. Over time this will mean replacing the brake fluid. Silicone brake fluid does not absorb moisture. While this seems to be an advantage, it isn't. Because the moisture is not absorbed into the fluid it ends up in the lowest point of the system, the calipers and wheel cylinders. As you know, water boils at 212˚F, so therein lies one of the problems with DOT5 brake fluid.

Another problem with silicone brake fluid is the fluid itself is compressible. That leads to a spongy pedal feel. I've never felt that the fact that silicone brake fluid doesn't damage paint to really be that big a deal.

If you switch over to the DOT-5 fluid you WILL have to change everything made of rubber in your brake system and flush out your hard line thoroughly, as it is not compatible with DOT-3 or DOT-4. If you do that and decide to switch back, you will have to change out everything rubber again.

The only entity that has gone completely with DOT-5 brake fluid is the US military, due to its superior cold weather properties, but they are in the process of phasing it out.

I removed mine and sent it to Bill today. Should be at his place on Monday. Still could use a spare, though.

As for brake fluid, on the old restored cars I use the silicone brake fluid because in cases like this, where some seepage starts that you don't notice til it's too late, I would have had to repaint the inner fender, and frame rail to repair the damage that regular brake fluid would have done to the area. I don't really notice any difference using the silcone fluid, the pedal had a nice firm, non-compressing feel to it, even with the seepage from the prop valve o-ring.

For modern cars where the braking system's maximum capability actually matters, (I used to run Castrol SRF in my viper race car years ago) yes, the best fluid with the highest boiling point was the way to go. That cars pedal felt like you were trying to compress a cinder block when applying full braking at speed.

I am restoring a 71 TA and need new proper porp valve as well, I have the aftermarket one and its completely different. does anyone have bills number/ address i'd like to have him redo my original one although its pretty rough, if someone has another spare it would be appreciated. let me know. thx

SO, Whats up with DOT #3 Synthetic fluid I see for sale??

You can pm Bill. He is 70RAIII on the forum. Great guy, he restores a bunch of different components.

It's marketing hype. All DOT 3 and DOT4 brake fluids are synthetic. Always have been, though now it's a sales marking thing to point it out. DOT 3 brake fluids are mixtures of glycols and glycol ethers. DOT 4 contains borate esters in addition to what is contained in DOT 3. They are all composed of synthesized chemicals.

Thanks Johnsma22 !! The 3 and 4 are still different then Dot #5 , correct? not compatible for a" top off" ?

That's correct. DOT 5 is silicone based, not glycol based. They are not compatible. You can use DOT 5 in a previous DOT 3/4 system only if all rubber parts are replaced and the system is thoroughly flushed out.

So, is there a brake fluid that will not harm paint that also doesn't have the issues that DOT 5 has? What is the best to use in our old cars?

Are you still needing a spare valve? I'm sure I can muster up a good used one.

Transamric, I pm'd you.

Got the proportioning/combination valve back from 70RAIII (Bill Oxley) who did a really nice job on it. He indicated that it was all stuck inside, so it wasn't really functioning as anything other than a T-fitting between the front and back fluid routes. Now it's actually working as designed, which is a good thing since if I recall correctly, one of the critical roles of this valve is to internally shift and block the internal passages if one circuit springs a leak and loses fluid. That way you still have braking power for the remaining circuit.

Another thing I noticed is that the purple DOT 5 silicone brake fluid turns yellow after a few years. Even the leftover, half a bottle I still had on the shelf, turned the same yellow. I'd imagine that means it's time to replace it all, which I did. I flushed the entire system and replaced it with new DOT 5 silicone brake fluid, about four bottles worth, to get all the old stuff out and completely flush the system of the four year old fluid.

The newly refurbished proportioning/combination valve, just back from Bill Oxley:

http://i466.photobucket.com/albums/r...b/S7005982.jpg

And after the installation and the brake bleed-a-thon:

http://i466.photobucket.com/albums/r...b/S7005983.jpg

NJSteve said:
Now it's actually working as designed, which is a good thing since if I recall correctly, one of the critical roles of this valve is to internally shift and block the internal passages if one circuit springs a leak and loses fluid. That way you still have braking power for the remaining circuit.



Yes, Steve.. you are correct.. If your rear lines were to be cut and loose fluid, the front brakes will still have full pressure if the internal piston is functioning properly. this is why so many of the "rebuilds" can actually be dangerous. Most just clean the exterior, maybe replate the metal parts and paint.. You have to get the internal piston out. On this model valve, I bet 20% or so I end up breaking trying to remove the internal piston.. Just never was really supposed to be a servacible part.. But they all have major gunk/thick varnish on them after 40 years of fluid gettting old, cars stitting idle for years etc.. And yes, your description is dead on. good luck with the brake system. Glad I could help.. Bill'

Is that supposed to be black like the master cylinder or is it cast.....hard to tell in the picture.

Black semi lacquer like the master cylinder. The original one from NJStevs car had remenants of black paint on it when I received it.. I have seen some service replacment "NOS" units that were just plain cast, but GM had parts like this lightly sprayed with black paint, as part of their black out programs on all cars . Inagine how quickly bare cast iron would start rusting on a car that sat on a lot in...let's say Houston or Memphis for a couple months...yes, black painted..

Great work Bill and great information.

Agree-everything Bill does is top notch.

Is there a rebuild kit for these or do you just need to dig up a few O-rings?