Dot 5 Fluid and CSSB Warning

[Larry M.]

Re: Dot 5 Fluid and CSSB Warning

That question was what the NHTSA experiment that used my car was about. The question was what happens if silicone fluid is simply bled through a system filled with DOT-3. The result was just what Joe said. The DOT-3 fluid around the pistons did not bleed out sufficiently. That fluid still absorbed (or had already absorbed) water, so it’s boiling point and rust potential stayed the same and negated the benefits of the silicone fluid, but there were no adverse effects from the mixture. Consequently, NHTSA recommended only starting silicone fluid in systems that had been thoroughly cleaned out.

The only problem I have seen with silicone fluid is that the reproduction master cylinder that Lone Star sells would not bleed properly with silicone fluid due to it higher viscosity. The passages between the reservoir and the bore are more restrictive on these GM Licensed reproductions which look like the original castings but have inferior machining. I got an original master cylinder sleeved and it worked fine. Maybe that is one of the reasons they discourage the use of DOT-5.


on

The Parker O-Ring Manual, which has been the industry standard for decades, clearly shows and then discusses use of specific EPDM (EPR family) rings/elastomers for use with DOT 3/4/5 fluids. They even provide special coding numbers for ordering. No where is is shown or mentioned that DOT 5 is an issue.

Now they also show that SBR rubber is also allowed per government and SAE regulations for brake fluids, but that DOT 5 compatibility is not nearly as good as for the DOT 3/4 fluids or for the EPDM rubber.

What is needed is what rubber/elastomer compound Lone Star, CSSB, Inc, and others are using for lip seals and o-rings, where is it sourced (US, Mexico, China), and also what DOT 5 fluids were shown to be issues. According to Parker, DOT 5 is not an issue when the proper EPDM o-rings are used.......and they state the code numbers for these compounds.

Larry

[David G.]

Re: Dot 5 Fluid and CSSB Warning

I have used dot 5 for many years in dozens of Corvettes and muscle cars.
I have used it in autocross cars as well as hillclimb cars.
It also occurs to me that since it has been used worldwide in military
vehicles that it must have some advantages.

Dave

[Larry M.]

Re: Dot 5 Fluid and CSSB Warning

I believe the military and some post office vehicles still use it. If it was not developed by/for the military, they are the ones that put it into the mainstream.

I still remember Terry M's discussion about military use.

Larry

[Terry M.]

Re: Dot 5 Fluid and CSSB Warning

I believe the military and some post office vehicles still use it. If it was not developed by/for the military, they are the ones that put it into the mainstream.

I still remember Terry M's discussion about military use.

Larry

Harley Davidson used DOT 5 at one time & still might.

[Gary C.]

Re: Dot 5 Fluid and CSSB Warning

Harley Davidson motorcycles from 1976 thru 2006/2007 used DOT 5. Mine, a 2004 FXDX that I am original owner was originally equipped with DOT 5 and will always have DOT 5. Why HD went away from DOT 5, simple - ABS. I would hate to fill master cylinder on the front right handlebar with the painted fuel tank located right below using DOT 3.

[Tom M.]

Re: Dot 5 Fluid and CSSB Warning

Larry, the military started using silicone decades ago because their vehicles sit for extended periods outside. Those of us near the coast constantly fight high humidity and standard brake fluid soaks up moisture like a sponge. Silicone has been a huge benefit for my military jeep restorations. Brake systems last decades vs the DoT 3 equipped vehicles.
This thread has references to EPDM compounds.
Who uses silicone O-rings and seals? Are these intended to be used with silicone fluid?
https://www.corvettecentral.com/65-8...-o-ring-192390

[Larry M.]

Re: Dot 5 Fluid and CSSB Warning

Larry, the military started using silicone decades ago because their vehicles sit for extended periods outside. Those of us near the coast constantly fight high humidity and standard brake fluid soaks up moisture like a sponge. Silicone has been a huge benefit for my military jeep restorations. Brake systems last decades vs the DoT 3 equipped vehicles.
This thread has references to EPDM compounds.
Who uses silicone O-rings and seals? Are these intended to be used with silicone fluid?
https://www.corvettecentral.com/65-8...-o-ring-192390

Tom:

The Parker O-ring Manual shows silicone o-rings to be UNSATISFACTORY for use with DOT 5 brake fluid. Google "Parker O-ring Handbook" and you can see all this info for yourself. The compatibility info is near the end of the book. Book is now a few hundred pages.

Larry

[Gary B.]

Re: Dot 5 Fluid and CSSB Warning

Tom:

The Parker O-ring Manual shows silicone o-rings to be UNSATISFACTORY for use with DOT 5 brake fluid. Google "Parker O-ring Handbook" and you can see all this info for yourself. The compatibility info is near the end of the book. Book is now a few hundred pages.

Larry

Larry,

Silicone O-rings not being compatible with silicone fluid is not the answer I would ever have expected. So much for my intuition.

Gary

[Mark E.]

Re: Dot 5 Fluid and CSSB Warning

This week one piston seal in the RF caliper started to leak. The calipers were sleeved and rebuilt with lip seals seven years and 2,000 miles ago.

To my surprise, when I disassembled the caliper I found crud and dirty fluid in the cylinders. I was surprised because the system was flushed with DOT 4 every two years (three times after the initial rebuilding). The leaky sleeve looked fine, but two others in that caliper had a groove worn where the seal rested.

So I just ordered two rebuilt front calipers with o-rings from Lone Star. They offer a "limited lifetime" warranty, but like CSSB, it's void if DOT 5 is used. My plan going forward is to flush every year with DOT 4 and take advantage of the warranty if necessary.

I like what I hear about DOT 5 but the voided warranty is a deal breaker.