autoalain

Lesson learned, bought new master, installed and tried everything to get a good pedal, finally thought bad master, pulled it apart. guess what all rubber failed inside....why??? I now know why,
my buddy closed up his shop, brought me tons of fluids, including a gallon of brake fluid, I poured out this fluid into a bowl, it has been mixed with some other fluid, who know what, but
it does not like rubber. lesson learned, buy a new bottle, tried to save $15.00 and now will cost me much more. Mike.

gbvette62

If you used DOT 5, that's probably the reason your rubber seals failed.

A few years ago, the US EPA outlawed the use of certain chemicals that were found in DOT 5. The new chemical make up of DOT 5 has been known to damage the rubber seals used in some master cylinders and calipers. I'm assume the same DOT 5 is likely being sold in Canada now too.

v2racing

As I have said many times here, I have been using DOT 5 brake fluid since the 1970's in everything including street, drag racing, land speed racing and road racing without one single issue. I have it in my current Vette today. I have rock hard brakes that function perfectly.

I have searched extensively for this supposed reformulation issue in the past when someone brought it up on this forum and have found zero info to support it. Nobody else was able to show evidence of it either. The only reformulation info I have found is that DOT 5 was first developed in the late 1960's for the military. It's final formulation was developed in the 1970's and it is still the same formula today.

The two main problems I have seen with DOT 5 are people putting it in systems with DOT 3 in them and people aerating the fluid by pumping the crap out of the brakes while bleeding and then not getting a hard pedal. Both of these are user caused issues, not the fluid.

Mike

Rodnok1

Ouch... Probably had solvent in it if destroyed rubber that quick.

jim2527

FWIW I just installed an O-ring kit from SSBC and they said warranty is void if DOT 5 fluid is used. IDK.

v2racing

I believe it is because of the bleeding issue. It's real easy to get air in and real tough to get it out once you've aerated DOT 5. The new part is always what is going to get blamed by the customer, so I figure the manufacturers figure why deal with it. My o-ring kit had the same DOT 5 disclaimer. I've had no issues with DOT 5 and these o-rings.

Mike

gbvette62

I too have used DOT 5 in the past, and with good results, but I'm told that DOT 5 has changed, and I've encountered problems with using new DOT 5. I have 2 customers return caliper sets to me, that had seals that turned to mush, and another who had it happen with a master cylinder. All three of them had just used fresh DOT 5. I have been selling Lonestar's calipers for over 20 years, and never had this happen before the last 2 years. Lonestar, Muskegon, CCSB and others are now including warnings with their brakes, that use of DOT 5 can void the warranty.

Below is a link to the regulation, that Lonestar told me was the one that caused the chemical make up of DOT 5 to be changed.

https://www.regulations.gov/document...2009-0767-0031

v2racing

Someone posted this EPA regulation before. I read and it pertains to ethylene glycol ethers which DOT 5 does not contain. DOT 3, 4, and 5.1 do however contain ethylene glycol ethers. Most of the restrictions were banning use of some glycols in paint and ink solvents.

Most of the brake rubber damage I have seen has resulted from contact with some sort of petroleum distillate such as solvent, carb cleaner or some cheap brake cleaners that have petroleum in them, which brake cleaners should never have. I'm not sure what happened in your customer's cases, but I have consistently used DOT 5 from the 70's up to this day and have yet to have a problem.

Mike

Fredtoo

Mineral oil / motor oil and similar hydrocarbons will eat the EPDM rubber seals in brake systems.

stock76

I have been using DOT 5 silicone fluid in my 1976 Vette since 1982 with no brake issues. Fronts are still original VBP lip seal calipers (rebuilt once) rears are VBP O-ring calipers replaced eight or nine years ago. VBP didn't have any lip seals in stock and talked me in to trying the O-rings. One rear caliper had one piston leaking slightly but I went ahead and replaced both calipers. No problems since. If memory serves, Silicone brake fluid was recommended by VBP and other rebuilders that were doing stainless steel sleeves back in the eighties.

My 1971 uses Pentosin Dot 4. That was what was in it when I got it and no reason to change. The Pentosin Dot 4 is pricey compared to other Dot 3 and 4 fluids.