65-66 Proportioning Valve Rebuild

[s2ms]

Thinking of taking another crack at rebuilding a proportioning valve. Tried this years ago on the valve currently in my 66 but was a miserable failure, probably due to undetected scoring in the bore, and had to have it re-sleeved. But I'm a glutton for punishment.

I know how to do the rebuild, my question is the best way to assemble everything for longer term storage? It will likely be awhile before I install it and assume assembling with brake fluid is not the best idea if it sits awhile? Is it OK to assemble with a light coat of WD-40, Boeshield, or similar? Or would that cause an issue mixing with brake fluid when I do install? Or...should I just bag the idea for now and wait to rebuild when I'm ready to install?

Thanks,
Dave

[NC TRACKRAT]

Dave, I, too gave it a try and, like you, failed miserably.  At $150 a pop, White Post Restorations did my last two.  Don't know what, if anything, they coated the bores with but, if I were doing the job, I'd use a light coat of silicone brake fluid which could easily be flushed out if conventional DOT3 were to be used.  The silicone is basically inert and would have no affect on the metal or rubber seals.

[Bob Gaines]

Thinking of taking another crack at rebuilding a proportioning valve. Tried this years ago on the valve currently in my 66 but was a miserable failure, probably due to undetected scoring in the bore, and had to have it re-sleeved. But I'm a glutton for punishment.

I know how to do the rebuild, my question is the best way to assemble everything for longer term storage? It will likely be awhile before I install it and assume assembling with brake fluid is not the best idea if it sits awhile? Is it OK to assemble with a light coat of WD-40, Boeshield, or similar? Or would that cause an issue mixing with brake fluid when I do install? Or...should I just bag the idea for now and wait to rebuild when I'm ready to install?Just my suggestion.

Thanks,
Dave

I would rebuild it with whatever brake fluid (silicone or conventional) that you plan on using. I would not use boeshield or wd 40 as it may have have a negative effort when mixed with brake fluid. Not sure how long of storage but bag the valve and a year or 2 in the sealed bag should not be a issue. People use NOS valves in a box that are decades old without issues mostly. If you decide to wait I would put the rebuild kit in a bag so it doesn't degrade. Who knows if the parts will be readily available when you are ready to rebuild years from now.

[Bob Gaines]

Dave, I, too gave it a try and, like you, failed miserably.  At $150 a pop, White Post Restorations did my last two.  Don't know what, if anything, they coated the bores with but, if I were doing the job, I'd use a light coat of silicone brake fluid which could easily be flushed out if conventional DOT3 were to be used.  The silicone is basically inert and would have no affect on the metal or rubber seals.

You are correct on the properties but I do not agree on your advice about flushing the silicone out. If you use silicone you will have to disassemble again to properly clean and re assemble with dot 3 if wanting to use the Dot 3. Same goes if you assembled it with Dot 3 and want to run silicone. When the two interact the reaction is a tendency to gel up. You may be able to flush out enough and you may not. You have to ask yourself is it really worth the gamble of contaminating your entire brake system. Do one or the other and if you change your mind disassemble ,clean and re assemble with desired brake fluid . That is my advice . Use it or not.   

[s2ms]

Dave, I, too gave it a try and, like you, failed miserably.  At $150 a pop, White Post Restorations did my last two.  Don't know what, if anything, they coated the bores with but, if I were doing the job, I'd use a light coat of silicone brake fluid which could easily be flushed out if conventional DOT3 were to be used.  The silicone is basically inert and would have no affect on the metal or rubber seals.

Thanks Stan. White Post also did the one currently in the car, which has worked flawlessly for at least 15 years. That one is a later service part, the one I'm thinking of rebuilding now is an OE valve with the correct machining and perfect date code.

I would rebuild it with whatever brake fluid (silicone or conventional) that you plan on using. I would not use boeshield or wd 40 as it may have have a negative effort when mixed with brake fluid. Not sure how long of storage but bag the valve and a year or 2 in the sealed bag should not be a issue. People use NOS valves in a box that are decades old without issues mostly. If you decide to wait I would put the rebuild kit in a bag so it doesn't degrade. Who knows if the parts will be readily available when you are ready to rebuild years from now.

Thanks Bob, a year or 2 is about right. It'll take me that long to want to do the job badly enough since it's a bit of a PITA to do just for cosmetic reasons.

[Bossbill]

I never use brake fluid to assemble hydraulic parts. Here's why:

[Bob Gaines]

I never use brake fluid to assemble hydraulic parts. Here's why:

You can also ask the people who rebuild them and warrenty them if they fail use. FYI if you have a wheel cylinder ,proportioning valve etc built at white post they will not assemble them with silicone. I have to disassemble ,clean and reassemble with silicone which is what I suggest for limited driving pleasure driven cars. At least it reassembles much easier once it is has been rebuilt . What a pain.

[s2ms]

I never use brake fluid to assemble hydraulic parts. Here's why:

Thanks Bill, never even knew that stuff existed! Found one source that said the Centric fluid is "Compatible with all DOT 3 and DOT 4 brake fluids".

[OldGuy]

Thinking of taking another crack at rebuilding a proportioning valve. Tried this years ago on the valve currently in my 66 but was a miserable failure, probably due to undetected scoring in the bore, and had to have it re-sleeved. But I'm a glutton for punishment.

I know how to do the rebuild, my question is the best way to assemble everything for longer term storage? It will likely be awhile before I install it and assume assembling with brake fluid is not the best idea if it sits awhile? Is it OK to assemble with a light coat of WD-40, Boeshield, or similar? Or would that cause an issue mixing with brake fluid when I do install? Or...should I just bag the idea for now and wait to rebuild when I'm ready to install?

Thanks,
Dave

The biggest problem of using a non-brake fluid (either DOT 3 or silicone) petroleum-based product (like the ones that you mentioned) is the incompatibility of the rubber parts, in the proportioning valve, with the assembly fluid. Petroleum-based products will cause swelling and degradation of the rubber and ultimately failure---which is not a good thing to happen on a brake-related component.

Frank

[NC TRACKRAT]

Understand your well-founded concern but, FWIW, I've switched a couple of systems over to silicone by thoroughly flushing and had no adverse effects. Just lucky I guess.

[Bossbill]

Thanks Bill, never even knew that stuff existed! Found one source that said the Centric fluid is "Compatible with all DOT 3 and DOT 4 brake fluids".

Dave -- The stuff I have is from another vendor (Bendix?) but it's the same idea.

[KR Convertible]

If the bore of the proportioning valve needs a sleeve, I use stainless.  Some people use brass because it's easier, but I prefer stainless.  With stainless you'll never have to worry about pitting in the bore again.  Assemble with your choice of fluid, cap the ports and store in a dry place.

[gt350hr]

     McKay also has brake assembly lube . Smaller semi clear bottle. Works great . Orielly's , Autozone , should have it.
    Randy

[s2ms]

Thanks to everyone for all the info!

Have the valve apart and cleaned up, generally in very good shape. The bore is also pretty good but the minor scoring is a little too much so will likely have it re-sleeved.

If the bore of the proportioning valve needs a sleeve, I use stainless.  Some people use brass because it's easier, but I prefer stainless.  With stainless you'll never have to worry about pitting in the bore again.  Assemble with your choice of fluid, cap the ports and store in a dry place.

I assume brass would be resistant to pitting as well? I've read different opinions about using brass or stainless, Some say brass is less prone to leaking since it's "softer" allowing seals to seat better. Others say stainless is better because it's more durable. Other opinions?

Thanks,
Dave

[Bob Gaines]

When in doubt sleeve. That is better then installing and have it leak right away or worse later. Messing up the paint with leaking conventional brake fluid is also something that would influence the decision to error on the side of caution IMHO.