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OK, let's start off with stating the obvious. There have been a whole lot of threads as of late concerning brakes. And the topic of DOT 5 fluid and the warnings on Corvette brake products not to use it.
Not long ago I put up a thread concerning a supposedly new caliper that came to me in poorly rebuilt condition. In that thread I posted up a photo of a O ring that came in a kit I purchased in a attempt to repair this garbage I paid good money for.
this O ring convertion kit came with what I feel where some really crappy looking O rings.
It was brought to light by a fellow former member that in the early days of these O ring convertions that the slight mould seam on the O ring would wear and then cause leaks. So the Corvette aftermarket sought out O rings with the seam offset.
My research seems to show that this is the approximate time the DOT 5 warnings came into being.
It seems that one rubber compound seems to work well with both DOT 3 / 4 and DOT 5. This is the EPDM rubber compound commonly used in brake parts throughout the automotive industry for approximately 50 years.
However, when special O rings where manufactured specifically for Corvette calipers. This is not the rubber compound that was used. Thus this crappy looking O ring that doesn't like DOT 5.
the rubber they use does play nice with DOT 3 and 4. But doesn't like DOT 5.
So I go into a major bearing and seal shop armed with a crappy O ring and ask them to get me a dozen of these in EPDM rubber. The guy looked through every book he had.
No dice. No one made a O ring in this size in this type of compound.
I am starting to see the problem here.
.
So, I says what compounds of rubber can you get this size O ring in?
the answer was 2 . One wasn't useful for a moving wear part whatsoever. The other was Viton. I know the Viton name as it is common with engine seals.
So, I did some more research.
Seams Viton isn't used in brake systems inspite of its good wear qualities in moving applications because it doesn't play well with DOT 3 and 4 brake fluid.
However, Viton plays very, very nice with silicone based fluids.
In fact the compound of choice with silicone based fluids.
So, I now have 4 , part number BS318V O rings that fit the pistons of a rear O ring conversion kit.
Now, using these O rings will absolutely not work with DOT 4. But according to everything I have read. Should work fine with DOT 5.
Now of course this is just for a rear caliper.
And this is a ongoing experiment. But I am fairly certain that running a Viton O ring in place of the supplied O rings with a O ring convertion kit should solve the problem.
As long as one doesn't change back to hydroscopic brake fluid.
Thought I'd open this up to discussion.
Me, I'm going to build one rear caliper and give it a trial.
Cause they are NOT going to make me change brake fluid.
(My parents didn't raise sheep).
I just have to ask......besides the fact that it won't damage paint......why do some just have to have DOT5? It has higher boiling properties but a scant few of us drive 10/10ths around Nurburing......
And why does a DOT3-4 fluid not work with Viton.....? Too thin and not as slippery?
It doesn't damage paint is a good one. The boiling point isn't bad, but like you point out. Kinda a mute point.
the why is the moisture. DOT 3 and 4 absorb moisture. They actually pull it right through the steel and rubber lines on a molecular level. You think your brake system is sealed? Not if you look at it under a microscope.
I do brake fluid moisture tests on every service, 6 days a week. Most vehicles over a year old fail.
Keep the water out of your brakes!
That's why we insist on it.
As per why DOT 4 doesn't like Viton. The same chemicals that attack paint also attack Viton.
A better question is. Why do they sell brake parts that don't work with off the shelf brake fluids off ALL kinds?
As per why DOT 4 doesn't like Viton. The same chemicals that attack paint also attack Viton.
A better question is. Why do they sell brake parts that don't work with off the shelf brake fluids off ALL kinds?
Because maybe those parts don't exist?
I have a story for you that you may find interesting.......about a year ago a guy got a hold of me and he had acquired the 32' 3 window coupe my Dad and I built in the early 2000's.......he sent me a bunch of pictures......one thing I noticed was that the original calipers and wheel cylinders were on this car from 20 years ago......I shot the calipers body color and the wheel cylinders were black........Dad had insisted putting DOT 5 in this car because our paint job turned out amazing and the master was on the firewall.....to fill it....you had to hold a bottle over the fender area....dad was nervous of that so DOT5 it was........and apparently still is......this system has been unchanged after 20 years and 6000 miles......so I believe in it for sure.....BUT, I have also replaced COMPLETE brake systems where some schlep poured DOT 3-4 in a DOT 5 system.......which eventually destroyed every part in the system......I put DOT 3-4 in everything because I worry about other people......
Bought my '73 in October last year. Opened the Master just last week thinking i would flush the system. Lavender/purple was staring me in the face - DOT 5. Master is new, Calipers appear to be rebuilds, new pads, new rotors on this car. Hand pump power bleeder came with the car - residual DOT five in the bottom. After reading the above - I hope all things with this car are good. It will be awhile before it is drive-able.
I've used DOT 5 forever in my car...but it was all new when I put it together 27 years ago. No leaks no issues...even when I later added Wilwood calipers.
While DOT 3/4 is hygroscopic and will absorb moisture.....Dot 5 doesn't.....but the moisture still gets in there and can/will find a spot to rest and will corrode when stuff sits around a lot. Just something be aware of. Moisture spread throughout the system absorbed in the fluid..or sitting in just one spot or two maybe. Stainless lines can help maybe.
If one were inclined to attempt a switchover from DOT 3 to DOT 5, you’d need a list of DOT 5 compatible parts. Seals, o rings, hoses, etc.
Does that exist?
ANYTHING that has rubber exposed to brake fluid. The old, water laden DOT-3 or DOT-4 fluid will leach out of any old rubber parts in the brake system. Rubber lines and seals all absorb the fluids.
I happen to see this thread as I was sitting here having coffee looking at a brake system for an old Saab with a manual 'gearbox'.
Just thought it was interesting, check this out. It needs DOT4 so I am taking the radical step of using DOT4
So, with the conundrum not resolved, a couple of questions for the group. Who has converted to DOT 5 fluid, had the seals fail bc the fluid ruined them, then concert back to DOT 3/4 with fresh seals and no further problems. On the other side, who's had DOT 5 for a few years or more and found puddled moisture (and resulting corrosion) inside a caliper or the master?
So, with the conundrum not resolved, a couple of questions for the group. Who has converted to DOT 5 fluid, had the seals fail bc the fluid ruined them, then concert back to DOT 3/4 with fresh seals and no further problems. On the other side, who's had DOT 5 for a few years or more and found puddled moisture (and resulting corrosion) inside a caliper or the master?
Who would admit to doing this? That sounds like a huge chore for no benefit.
It is resolved. If you have (old) Buna-N seals, either fluid should work, but your brakes probably leak due to age and/or heat. If you are using DOT 5, you need Viton seals. If you are using DOT 3, 4, or 5.1, you need EPDM seals.
I've been running DOT 5 for over 30 years. I recently replaced one caliper as it was one that had been replaced by the original owner of my car. When I took it apart I found only one half had been sleeved. So I purchased a new one. The new one turned out to be less than satisfactory. So I thought I'd clean it up and try putting O ring pistons and seals in it.
I ran a thread about this poor quality caliper not all that long ago.
at any rate shortly after I purchased this car, 2 other calipers started leaking. So instead of replacing all 4. I replaced 3 as the original owner had already replaced the one. It was at that time the car was converted to Dot5. As a motorcycle mechanic I had a good supply of it as back then that's all we used in Harley's.
So,
None of my other 3 calipers leak . Nor have they all these years. I did replace a master cylinder in the late 90's. But didn't blame it on anything other than it was 20 years old at the time. A rebuilt unit from the local Auto parts store went in and is still working fine 20 plus years later with DOT 5 in it.
back in the 80's and 90's none of our replacement brake parts came with a warning about DOT 5.
Who would admit to doing this? That sounds like a huge chore for no benefit.
Who? Someone who had it happen and wants to share the experience.Then got scaredof DOT 5 and went back. The conundrum is that there are forum members who wont touch DOT 5 fluid with a 10 ft pole, for all sorts of reasons, good and otherwise. I read all sorts of speculation about what MIGHT happen, but no one ever comes out and says it DID happen. I just want to hear a real story. Like water collecting in the low spots. Good in theory, but who's actually seen that in his brakes?
I'm NOT an anti DOT 5 crank. I put the stuff in my fresh dry brake system 25 years ago and haven't had a minute's trouble since. That's with cheap-o parts store lip seals in the calipers. Are they Buna-N? EPDM ? Dang if I know. I've had to replace one every now and then and don't bother to look at the insert in the box because I've never had trouble.
For reference I bought an O ring caliper kit about 20 years ago. I knew it was going to be trouble even before putting the calipers back on bc the seals were too tight in the bores. I converted back to lip seals and am still hard to convince that o ring seals on C2/C3 calipers are any good. Am I wrong ? Maybe. Just understand that some of the resistance to DOT 5 may be from bad experience. I still haven't seen a forum member describe one, though.
I don't know that it is a conundrum that folks have their preferences. While I AM an anti DOT 5 crank, I hope that there is enough information in this thread that folks can find the information they need to use whatever brake fluid they want without issues.
If you want to run DOT 5, and you don't have a set of NOS Buna-N seals, perhaps you can find someone to sell you Viton seals, or order them yourself from McMaster (likely O-ring only). Don't forget the master cylinder and combination valve, too.
Unlike, say, polyurethane bushings, which many folks soured to based on bad batches in the past, NEW brake bits now come with big warning stickers on them. This is the box my high-heat O-ring kit came in from CSSB Inc, which presumably contained EPDM O-rings.
If you want to run DOT 5, and you don't have a set of NOS Buna-N seals, perhaps you can find someone to sell you Viton seals, or order them yourself from McMaster (likely O-ring only). Don't forget the master cylinder and combination valve, too.
...
This is the box my high-heat O-ring kit came in from CSSB Inc, which presumably contained EPDM O-rings.
EPDM is an "old school" elastomer for brake components. It's perfectly fine with silicone fluid, as well as the other DOT fluids, and always has been. The Raybestos caliper seal kits contain EPDM seals.
Don't presume that CSSB calipers use EPDM - maybe call them and find out what they purchase. I believe the boxes contain the warning because they are not strictly sticking to one elastomer or supplier and are DOT 3/4 elastomer shopping for best price.
The O ring convertion kit I purchased is cssb branded. And has the DOT 5 warning on it. The Orings look and feel cheesy.
I honed my old caliper, it's well within spec. Not so much for the "New" one I purchased. I assembled it with Viton O rings. But it'll be a couple weeks before I get the chance to install it as I have other projects at the moment. But I will keep you all posted.
So, with the conundrum not resolved, a couple of questions for the group. Who has converted to DOT 5 fluid, had the seals fail bc the fluid ruined them, then concert back to DOT 3/4 with fresh seals and no further problems. On the other side, who's had DOT 5 for a few years or more and found puddled moisture (and resulting corrosion) inside a caliper or the master?
I tried DOT5 in one car, with new parts that never had any other fluid in them. I dumped it out a few years later and it looked pretty shitty for a fluid that is supposed to remain "perfect" forever. No better than any of the DOT4 I flush, because I do flush my vehicles brakes. I've never bothered with DOT5 again since then. Just don't see any point. It's like motor oil. Lots of postings and talk, but no proof that exotic oil does better at protecting an engine than a cheaper but still high quality oil.
The DOT 5 brake fluid conundrum.
