65-66 Proportioning Valve Rebuild

[KR Convertible]

I would think the rubber seal would work the same on either brass or stainless, provided the surface finish is the same.  The piston in the valve moves very little, all of the wear will be in one small area,  so I prefer stainless  If I remember correctly, I used a 1/2" stainless plumbing nipple and machined the OD and ID to make the sleeves.

[gt350hr]

   Dave ,
      Mine was done with brass 30 years ago along with my wheel cylinders and they have been trouble free ever since.
     BTW there are two different types of "internals" . The kits only work with the FAR more common "later" version. The "early" valve is anodized light purple (for reference).
     Randy

[OldGuy]

Guys, from a "pitting" standpoint, either brass or stainless (assuming a 300-series material) is a toss up. From a "leak" standpoint, once again a toss up as far as leaking past the chevron seals in the bore. I believe that most leaks are from a void in the "glued joint" between the iron cylinder and the sleeve. The sleeves are generally installed using a Loctite-type product to PERMANENTLY affix the sleeve to the bore.

From a "machining standpoint", brass is far easier to machine/hone to size than stainless so the price to install and finish the sleeves could be reflected in the out-the door price.

I don't think that you can go wrong using EITHER material for the sleeve. As far a which type of brake fluid to use, I feel that DOT 5 is a better choice for any car that isn't a daily driver. I feel that the "pros" out way the "cons". I know that I'll probably get some push back for that statement but that's my view of the world.

Frank

[s2ms]

Great info, thank you all!

[Bob Gaines]

Guys, from a "pitting" standpoint, either brass or stainless (assuming a 300-series material) is a toss up. From a "leak" standpoint, once again a toss up as far as leaking past the chevron seals in the bore. I believe that most leaks are from a void in the "glued joint" between the iron cylinder and the sleeve. The sleeves are generally installed using a Loctite-type product to PERMANENTLY affix the sleeve to the bore.

From a "machining standpoint", brass is far easier to machine/hone to size than stainless so the price to install and finish the sleeves could be reflected in the out-the door price.

I don't think that you can go wrong using EITHER material for the sleeve. As far a which type of brake fluid to use, I feel that DOT 5 is a better choice for any car that isn't a daily driver. I feel that the "pros" out way the "cons". I know that I'll probably get some push back for that statement but that's my view of the world.

Frank

You heretic you.

[OldGuy]

Guilty as charged.

[sg66]

Whitepost rebuilt mine 4 years ago and when I took the car out of storage this spring, there was a small puddle of fluid on the ground. I've traced it back to the rear of the prop valve, probably o-ring. I use DOT 5 and have read it can cause newer rubber to swell. Anyone else run into this and are there replacement o-rings that are better suited for this? The brake pedal is otherwise firm and doesn't go to the floor.

[OldGuy]

Whitepost rebuilt mine 4 years ago and when I took the car out of storage this spring, there was a small puddle of fluid on the ground. I've traced it back to the rear of the prop valve, probably o-ring. I use DOT 5 and have read it can cause newer rubber to swell. Anyone else run into this and are there replacement o-rings that are better suited for this? The brake pedal is otherwise firm and doesn't go to the floor.

I am surprised that you had that type of o-ring failure using DOT 5 fluid. I wouldn't have been as surprised if you were using DOT 3 or 4 fluid. DOT 5 fluid is a very "inert" fluid that is reasonably compatible with many o-ring materials. Having said that however, the recommended o-ring material for either glycol-based (DOT 3 and 4) or silicone-based fluid is ethylene propylene (EPDM). This information was taken from the Parker Hannifin O-ring Handbook.

I hope this helps.

Frank

[sg66]

Whitepost rebuilt mine 4 years ago and when I took the car out of storage this spring, there was a small puddle of fluid on the ground. I've traced it back to the rear of the prop valve, probably o-ring. I use DOT 5 and have read it can cause newer rubber to swell. Anyone else run into this and are there replacement o-rings that are better suited for this? The brake pedal is otherwise firm and doesn't go to the floor.

I am surprised that you had that type of o-ring failure using DOT 5 fluid. I wouldn't have been as surprised if you were using DOT 3 or 4 fluid. DOT 5 fluid is a very "inert" fluid that is reasonably compatible with many o-ring materials. Having said that however, the recommended o-ring material for either glycol-based (DOT 3 and 4) or silicone-based fluid is ethylene propylene (EPDM). This information was taken from the Parker Hannifin O-ring Handbook.

I hope this helps.

Frank

I was reading on a Corvette forum that back in 2015, the EPA changed manufacturing regulations which may have effected rubber parts. I can't find the original thread but this is what they were referring to.

Corvette Stainless Steel Brakes voids warranty if silicone fluid is used: http://cssbinc.com/dot5warrantynew.01.pdf

Links to EPA page: https://www.regulations.gov/document?D=EPA-HQ-OPPT-2009-0767-0031

[Bob Gaines]

What a disappointing dvelopement.

[OldGuy]

Whitepost rebuilt mine 4 years ago and when I took the car out of storage this spring, there was a small puddle of fluid on the ground. I've traced it back to the rear of the prop valve, probably o-ring. I use DOT 5 and have read it can cause newer rubber to swell. Anyone else run into this and are there replacement o-rings that are better suited for this? The brake pedal is otherwise firm and doesn't go to the floor.

I am surprised that you had that type of o-ring failure using DOT 5 fluid. I wouldn't have been as surprised if you were using DOT 3 or 4 fluid. DOT 5 fluid is a very "inert" fluid that is reasonably compatible with many o-ring materials. Having said that however, the recommended o-ring material for either glycol-based (DOT 3 and 4) or silicone-based fluid is ethylene propylene (EPDM). This information was taken from the Parker Hannifin O-ring Handbook.

I hope this helps.

Frank

I was reading on a Corvette forum that back in 2015, the EPA changed manufacturing regulations which may have effected rubber parts. I can't find the original thread but this is what they were referring to.

Corvette Stainless Steel Brakes voids warranty if silicone fluid is used: http://cssbinc.com/dot5warrantynew.01.pdf

Links to EPA page: https://www.regulations.gov/document?D=EPA-HQ-OPPT-2009-0767-0031

Wow, talk about "light reading"

[s2ms]

Whitepost rebuilt mine 4 years ago and when I took the car out of storage this spring, there was a small puddle of fluid on the ground. I've traced it back to the rear of the prop valve, probably o-ring. I use DOT 5 and have read it can cause newer rubber to swell. Anyone else run into this and are there replacement o-rings that are better suited for this? The brake pedal is otherwise firm and doesn't go to the floor.

Did you flush the valve after getting it back from White post? Confirmed recently they assembly and test their rebuilds using Dot 3.

[sg66]

Did you flush the valve after getting it back from White post? Confirmed recently they assembly and test their rebuilds using Dot 3.

Yes I did take it apart and clean it before adding DOT5. All lines and rear cylinders were new, Jim Cowles did the front calipers for DOT5 and the MC was cleaned and previously had DOT5 for 25+ years. 

The vette thread I was looking at is: https://www.corvetteforum.com/forums/c1-and-c2-corvettes/3887928-how-risky-is-using-dot-5-a.html

It seems that WhitePost and LoneStar both say the silicon fluid is not compatible with "their" seals which brings me back to who makes seals and o-rings that are still compatible with silicon fluid?

I know Scott Drake makes a kit but can't find any info on the material used or compatibility with DOT5.

Another good thread with o-ring and seal specs: https://www.allfordmustangs.com/forums/classic-tech/1035929-66-gt-proportional-valve-issues.html

I plan to pull it apart this week to see whats going on and measure the seals before they have a chance to dry.

[NC TRACKRAT]

I don't have a degree in chemical engineering, just one in industrial engineering, but I find it difficult to envision a fluid that won't harm paint would affect rubber o-rings.  The proportioning valve in 6S1467 was re-built by White Post and has been in service for a number of years with no adverse effect noted.

[sg66]

  BTW there are two different types of "internals" . The kits only work with the FAR more common "later" version. The "early" valve is anodized light purple (for reference).
     Randy

Circling back on this to share what I found and also ask Randy what in the kits doesn't work with the early purple anodized valve which is what I have?

1.) Inside clearly had signs of rust on the un-sleeved part of the cylinder which started to find its way past the rubber o-ring on the end cap. How moisture found it's way in is a mystery.

2.) According to Parker Hannifin, o-ring materials react differently with DOT3, 4 or 5 and EPDM is recommended for all. Most o-rings like Danco sold in hardware stores are Nitrile (NBR)

3.) I don't know what White Post uses but the o-ring on the end cap had a thickness of 0.0955". For comparison, a #17 Danco measures around 0.1025". I bought 119-E70 EPDM 70 o-rings which are around 0.1050".

4.) These measurements don't sound like much but the cast iron where the o-ring sits has some minor pitting. Machining that smooth would open the gap to fill with the o-ring and in the end likely create a bigger leak.

5.) The final piece is the c-clip on the end. The one from White Post measured 0.0500". For comparison, I bought a few at Ace that ranged from 0.0500 to 0.0520". This matters because when the adjusting screw and spring are tightened, they want to push the end cap away from the body and reduce the sealing potential of the o-ring.

6.) Between the o-ring and c-clip I reduced the area to be sealed by around 0.0115" (between the red and blue lines)

Back to Randy's comment, mine is the earlier valve so the o-rings mentioned and measurements may not be relevant for later valves.

Also FWIW, I bought some extra EPDM and Nitrile o-rings and soaked each in DOT 5 and DOT 3 for a week and the only measurable swelling was the Nitrile rings in DOT 3.

Steve-