Dot 5 Fluid and CSSB Warning

[Richard M.]

Re: Dot 5 Fluid and CSSB Warning

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

Yes I've heard the identical reason why DOT 5 cannot be used in ABS equipped vehicles. I actually think I've read it on some DOT 5 labels as being a ABS incompatibility caution. The ABS valves fire on and off rapidly in a panic stop or as part of traction control systems ability to apply braking at individual wheels. Allegedly this fast action helps create the "micro" bubbles(as I call them).

Whenever I use DOT 5 on a new brake system I use extreme care when pouring the fluid and when bleeding. The "pump-up-the-pedal" action has to be slow and easy. I typically use a Mity-Vac initially to draw to each corner, then follow up with a gravity bleed at all 4 corners simultaneously and all is perfect.

Rich

[Edward B.]

Re: Dot 5 Fluid and CSSB Warning

I've never been tempted to use DOT5, so I probably haven't been paying sufficient attention to its properties and the recommendations for its use. It was a real eye-opener to read about DOT5's incompatibility with ABS which, when explained, makes perfect sense. Further research revealed many discussions on the topic which prompts me to wonder why DOT has not required a change in the labeling for DOT5 fluid advising against its use with ABS. Isn't this a basic safety issue about which the consumer should be informed?

[Richard H.]

Re: Dot 5 Fluid and CSSB Warning

Edward, I have 2 different brands of DOT5 out in my garage, and both containers are labeled "Not for use with ABS braking systems". Can't remember where I learned that, but it was back in the mid-90's when I began using silicone fluid.
Well, maybe my '57 can be a "test mule" of sorts as I just installed the master cylinder last week and filled it up with Dot5. Everything in the braking system is new. Should have it on the road within a month, so we shall see.

Rich

[Duke W.]

Re: Dot 5 Fluid and CSSB Warning

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. testing, but I may do some more

The response you got from the vendor doesn't make any sense. There are tests and requirements to achieve the various DOT certification levels. The tests are likely the same, but, for example DOT 4 must have a higher dry and wet boiling point than DOT 3. Saying that there are no "testing formats" for DOT 5 is nothing short of ludicrous. If there are no "testing formats" for DOT 5 how does a product achieve the DOT 5 certification?

[Michael W.]

Re: Dot 5 Fluid and CSSB Warning

why DOT has not required a change in the labeling for DOT5 fluid advising against its use with ABS. Isn't this a basic safety issue about which the consumer should be informed?

Very few car owners even look at brake fluid levels, never mind top them up. Even fewer do their own fluid changes. The tiny number who do their own work almost always look up the specs in the manuals and simply follow what the OEM recommends. The minute number that will ignore the OEMs spec and choose a non-recommended alternative product instead would most likely also ignore any cautions against it's use.

But then, there's the Darwin Awards to consider.........

[Richard M.]

Re: Dot 5 Fluid and CSSB Warning

AGS Fluid has the ABS usage warning. NAPA/MAC's/Balkamp not a word about ABS usage.

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

I use Cartel DOT 5.
This is from their brochure:

• • NON HYGROSCOPIC - does not absorb water, thus eliminating corrosion and deterioration
  • Dry boiling point exceeds 600 degrees Fahrenheit
  • Compatible with natural and synthetic rubber components
  • Never needs replacement
  • Doesn't harm painted surfaces
  • Lubricates all moving parts
  • Simple changeover - just perform normal "brake bleeding job"
  • Packaged in 8 oz, 12oz, quarts (32 oz), gallons,2-1/2 Gallon, and 55 gallon drums

**** NOT RECOMMENDED FOR ABS BRAKE SYSTEMS******

This is on the bottle:

[Richard H.]

Re: Dot 5 Fluid and CSSB Warning

I use Cartel DOT 5.
This is from their brochure:

• • NON HYGROSCOPIC - does not absorb water, thus eliminating corrosion and deterioration
  • Dry boiling point exceeds 600 degrees Fahrenheit
  • Compatible with natural and synthetic rubber components
  • Never needs replacement
  • Doesn't harm painted surfaces
  • Lubricates all moving parts
  • Simple changeover - just perform normal "brake bleeding job"
  • Packaged in 8 oz, 12oz, quarts (32 oz), gallons,2-1/2 Gallon, and 55 gallon drums
  
  

**** NOT RECOMMENDED FOR ABS BRAKE SYSTEMS******

This is on the bottle:

Jim, they could probably instill a little more confidence in me using their product if they could spell "recommended" and "systems" properly. Sheesh!

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

Jim, they could probably instill a little more confidence in me using their product if they could spell "recommended" and "systems" properly. Sheesh!

They should have had someone proof read the label prior to printing but to me, it's no big deal. The fact that they've been selling DOT 5 for 40+ years and it has worked perfectly for me for that long as well is more important.

[Jeff J.]

Re: Dot 5 Fluid and CSSB Warning

After speaking with some reputable brake part vendors and rebuilders that have been in the industry for several years, it is apparent to me the problem is with a new formulation of DOT 5 silicone brake fluid driven by EPA regulations to eliminate Ethylene Gycol Ethers. The link below is as included on labeling of some brake part vendors and actually includes EPA response to a public comment regarding brake system use. The parts vendors and rebuilders have indicated the issue is not with the seal materials as some have suggested.

I thought maybe these labels were primarily for legal reasons to protect vendors from people that mixed different types of fluid in their silicone brake systems (including DOT 5.1 which is not compatible with DOT 5) or for complaints about soft brake pedal feel. However, this is not the case.

One well respected brake and hydraulic parts rebuilder told me they conducted their own compatibility testing by soaking brake seals in a variety of brake fluids and determined it is the new formulation that is the problem. hey indicated it doesn't take any special circumstances such as high temperatures or extended exposure times. They said seal swelling and degradation happens very quickly. Furthermore, they even conducted chemical analysis of old and new DOT 5 silicone fluid to confirm there are differences in the formulations.

Although I've had silicone brake fluid in my 1966 Convertible for 17 years and have had no problems what so ever, I'm going to stay away from it for a complete brake rebuild I'm contemplating on my 1972 Coupe which has recently developed a caliper seal leak. I'll use DOT 3/4 and wait to see if a better silicone fluid becomes available.

What I haven't yet figured out is why haven't the silicone manufacturers figured out how to make the fluid compatible. Surely, their sales are down and customer complaints have increased. Based on rebuilder feedback, I don't know who could be buying and using the stuff. Perhaps a more compatible formulation is on the way. In the meantime, when and if necessary, I'll top off my 1966 with silicone fluid "bled" years ago when my 1966 brake system was new, clean.

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

[Jim L.]

Re: Dot 5 Fluid and CSSB Warning

After speaking with some reputable brake part vendors and rebuilders that have been in the industry for several years, it is apparent to me the problem is with a new formulation of DOT 5 silicone brake fluid driven by EPA regulations to eliminate Ethylene Gycol Ethers.

Jeff, when did this new formulation come into being? A scan of MSDS for silicone fluid published over the last 10 years shows no change in composition over that interval. Did the change happen farther back in time?

Also what was the old formulation? And what is the new formulation?

Jim

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

After speaking with some reputable brake part vendors and rebuilders that have been in the industry for several years, it is apparent to me the problem is with a new formulation of DOT 5 silicone brake fluid driven by EPA regulations to eliminate Ethylene Gycol Ethers.

I think you have DOT 5 and 5.1 confused. DOT 5 is polydimethylsiloxane (silicone) based. DOT 3-4-5.1 are all glycol based.
I don't know who your "reputable vendors" are but Wilwood, who is one of the largest aftermarket brake manufacturers and been in business 40 years, has no problem with DOT 5 and even sell it themselves.

[Larry M.]

Re: Dot 5 Fluid and CSSB Warning

I think you have DOT 5 and 5.1 confused. DOT 5 is polydimethylsiloxane (silicone) based. DOT 3-4-5.1 are all glycol based.
I don't know who your "reputable vendors" are but Wilwood, who is one of the largest aftermarket brake manufacturers and been in business 40 years, has no problem with DOT 5 and even sell it themselves.

I agree...........I think the key for those of us using DOT 5 is to buy from the major brake vendors that sell it along with brake hardware. My DOT 5 fluid comes from Stainless Steel Brake Company, the company that pioneered SS sleeving of the Corvette brake calipers in the 1970's. No issues for me in 23 years.

I would avoid DOT 5 from unknown sources or imported.

Larry

[Mark E.]

Re: Dot 5 Fluid and CSSB Warning

DOT5 fluid (silicon based) is not compaitble with certain types of rubber compounds which include most rubber compounds used in the break systems of very old vehicles. So its the combination of the type of fluid AND what it comes in contact with. There are are also water-absorption differences between DOT5, which is silicon based, and DOT2, 3, 4 AND 5.1. DOT5 does not absorb water which is why it hase a much higher temperature rating. DOT 5.1 contains siicone (70%) but is formulated to be compatible accross a wider range of rubbers and has the same temperature rating as DOT5.



Below is an excerpt from an article which is very detailed and will put you to sleep. http://www.buckeyetriumphs.org/techn...luid/Fluid.htm

This made me Google "buckeye triumph". A nickname for a car I didn't know? No, a car club in Ohio.

[Jim D.]

Re: Dot 5 Fluid and CSSB Warning

DOT 5.1 contains siicone (70%) but is formulated to be compatible accross a wider range of rubbers and has the same temperature rating as DOT5.

You sir, are 100% wrong on this point.