Dot 5 Fluid and CSSB Warning

[Gary B.]

Re: Dot 5 Fluid and CSSB Warning

This is a decal on Lone Star's boxes.

I quit using Dot 5 fluid probably 5-years ago, maybe longer. I have been care-taker for a persons collection of cars. Most have been sold off now, but he absolutely refused to use anything but DOT 5 fluid. Did not want to hurt the paint. So, about every 12 to 18 months, calipers would start to leak, bring it home, put new calipers on. Good business, especially for the brake people.

The 64, most of the time, would not last 12-months. Every spring, I would take apart the master cylinder, wheel cylinders and put new seals in. The old seals would look like your hands do after being water for a long time. All wrinkled up, swelled up, hard to remove.

The effect of DOT 5 on british cars is even more profound. They leak right away. Usually cannot get it out of the shop into the customers hands.

I was told it was a change in the seal compound, the rubber is not compatible to DOT 5. But, I do not know.

Ever wonder why NO car manufacturer uses DOT 5? I suspect it is more than the cost of the fluid.

I only have one can in the shop. It is an OLD OLD metal can used on Terrys car. It would be fun to have a chemical analysis done, see what has changed.

I use DOT 4 in everything now and do not have any problems. So much for job security?

Gary Bosselman

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

Ever wonder why NO car manufacturer uses DOT 5? I suspect it is more than the cost of the fluid.

Wonder no more - DOT 5 fluid is not compatible with the anti-lock brake systems that all car manufacturers now use.

I've used DOT 5 in every car I've built (dozens) over the last 40+ years. The DOT 5 in my 60 was installed in 1986 and it has never had any issues with the brakes.

The DOT 5 topic is no different than the zinc in oil, ethanol in gas, unleaded gas & hardened valve seats etc. controversies. Lots of opinions not backed by actual experience and many that simply regurgitate what they read on the internet.

[Terry M.]

Re: Dot 5 Fluid and CSSB Warning

This is a decal on Lone Star's boxes.

I quit using Dot 5 fluid probably 5-years ago, maybe longer. I have been care-taker for a persons collection of cars. Most have been sold off now, but he absolutely refused to use anything but DOT 5 fluid. Did not want to hurt the paint. So, about every 12 to 18 months, calipers would start to leak, bring it home, put new calipers on. Good business, especially for the brake people.

The 64, most of the time, would not last 12-months. Every spring, I would take apart the master cylinder, wheel cylinders and put new seals in. The old seals would look like your hands do after being water for a long time. All wrinkled up, swelled up, hard to remove.

The effect of DOT 5 on british cars is even more profound. They leak right away. Usually cannot get it out of the shop into the customers hands.

I was told it was a change in the seal compound, the rubber is not compatible to DOT 5. But, I do not know.

Ever wonder why NO car manufacturer uses DOT 5? I suspect it is more than the cost of the fluid.

I only have one can in the shop. It is an OLD OLD metal can used on Terrys car. It would be fun to have a chemical analysis done, see what has changed.

I use DOT 4 in everything now and do not have any problems. So much for job security?

Gary Bosselman

That OLD, OLD can is STP Brand made by Dow Chemical Corp. I have more at home.

If anyone has access to a mass spectrometer I would be happy to offer some fluid for testing. I knew some people (now retired) with a chemical addiction back when.

It certainly would be a relief to get to the bottom of this issue.

[Jeff B.]

Re: Dot 5 Fluid and CSSB Warning

Hi Gary,
Your post is very interesting since you saw this first hand. Yours is the only incidence I have seen where the seals are actually deformed in a short (or any) period of time using DOT 5. I have a few classis cars with DOT 5 and when I take something apart it still looks new. I'm vary curious about what the difference is since silicone compounds don't seem to react with much of anything that is rubber or plastic. Is it possible that in your case the owner had used a petroleum based solvent to clean the brake parts or lines, or a petroleum based lubricant on assembly? It takes very little residue of those products to damage the seals. The mystery continues!

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

I quit using Dot 5 fluid probably 5-years ago, maybe longer. I have been care-taker for a persons collection of cars. Most have been sold off now, but he absolutely refused to use anything but DOT 5 fluid. Did not want to hurt the paint. So, about every 12 to 18 months, calipers would start to leak, bring it home, put new calipers on. Good business, especially for the brake people.

Everybody, well almost everybody, knows that C-2 & C-3 calipers with factory lip seals will start leaking if left unused. To prevent them from leaking, once a month, you should apply the brakes to exercise the seals. That applies regardless of the type of brake fluid used.

[Jeff B.]

Re: Dot 5 Fluid and CSSB Warning

Jim,
I tend to agree. In America we are very regulated which is sometimes a pain. But the DOT regulations for the most part have been well thought out and trustworthy. DOT 5 is approve for use on all brake systems without antilock features, simple as that. And the antilock issue is due to the compressibility and air retention, not a problem with seals. All seals sold in America should be SAE compliant, which requires compatibility with DOT approved fluids. The SAE J-1603 test requires placement of the seals in each fluid at 248 deg F for 70 hours and then measures the expansion, which must meet a certain tolerance. The document on the CSSB site shows an overly expanded seal after an (apparently private) test was done with DOT 5. I have a hard time with this data and if anything it seems to suggest a problem with the rubber or testing procedure more than a systemic issue with DOT 5.

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

Jeff, Great post. I can't believe that DOT 5 will destroy, swell or eat up seals but is 100% harmless to our delicate paint jobs. That simply doesn't make sense.

[Larry M.]

Re: Dot 5 Fluid and CSSB Warning

Everybody, well almost everybody, knows that C-2 & C-3 calipers with factory lip seals will start leaking if left unused. To prevent them from leaking, once a month, you should apply the brakes to exercise the seals. That applies regardless of the type of brake fluid used.

Jim:

I have been able to go for 2 months without issues............but I won't push it any longer than that. Installed DR VETTE SS sleeved calipers with lip seals and used SS Brake Corp DOT 5 fluid back in 1995. No issues so far.

Larry

FWIW: CSSB now owes the DR VETTE brake lineup.

[Gene M.]

Re: Dot 5 Fluid and CSSB Warning

Next time doing anything with rubber brake parts take notice of where even the well known brake suppliers obtain the rubber parts from. Can you spell c-h-I-n-a. My reaction is to give it right back.

Many times it is molded right in the rubber part. ........junk...... it's getting harder and harder to get any quality parts just to keep these old cars running.

[Terry M.]

Re: Dot 5 Fluid and CSSB Warning

Everybody, well almost everybody, knows that C-2 & C-3 calipers with factory lip seals will start leaking if left unused. To prevent them from leaking, once a month, you should apply the brakes to exercise the seals. That applies regardless of the type of brake fluid used.

Jim
While "everyone knows that" I don't do it; and with about 40 years on my car I have had zero issues with the brakes. BUT, as I said in my other post all my brake parts are 40 to 50 years old and the DOT5 brake fluid is around 40 years old. I think it is clear that there is a difference either in modern brake parts, modern DOT5, or both.

[Jeff B.]

Re: Dot 5 Fluid and CSSB Warning

CSSB got right back to me today and sent me test results from their manufacturer of their brake rubber showing full compliance with the SAE J1603 testing. The have been very responsive to my questions. What is interesting is that the testing fluid that's is used for the seal compatibility test (and other tests) is glycol based, not silicone. The manufacturing company also commented that neither SAE or OEM have testing formats for DOT 5 fluids. So once again I got schooled - but I always welcome that. I guess that explains why there is such a controversy. I'm not sure if the DOT 5 fluid manufacturers do any testing, but I may do some more research.

[Brad H.]

Re: Dot 5 Fluid and CSSB Warning

Have used #5 in my Vettes for 15 years with no problem. Salesmen...there ya go.

[Joe L.]

Re: Dot 5 Fluid and CSSB Warning

Some time ago I learned somewhere that a certain type of process used in the manufacture of brake system rubber parts had been dropped, at least for SERVICE brake parts for older applications. As I recall, it was a process or treatment that was expensive and this was the impetus to drop it. I just don't recall all the details of it; I wish I did. In any event, I think this is the root cause of the problems described in this post. However, I think the problems would manifest themselves whether DOT 3/4 or DOT 5 is used, although the latter might be slightly more susceptible.

[Edward B.]

Re: Dot 5 Fluid and CSSB Warning

Wonder no more - DOT 5 fluid is not compatible with the anti-lock brake systems that all car manufacturers now use.

This is the first time that I ever heard this explanation. Do we have any more information on the anti-lock system issue?

[Jim L.]

Re: Dot 5 Fluid and CSSB Warning

This is the first time that I ever heard this explanation. Do we have any more information on the anti-lock system issue?

The pumping action when the ABS function kicks in is thought to trap air in the DOT5 fluid.