DOT 5 - Is this new to anyone else?

[Gerry G.]

Re: DOT 5 - Is this new to anyone else?

Were it gets confusing is when you go buy brake fluid and find that there is dot3 synthetic dot4 synthetic and dot 5 synthetic,Now what!!!!!!!!!!!!!!!!!

[Jim L.]

Re: DOT 5 - Is this new to anyone else?

Were it gets confusing is when you go buy brake fluid and find that there is dot3 synthetic dot4 synthetic and dot 5 synthetic,Now what!!!!!!!!!!!!!!!!!

It's not confusing. All brake fluid is synthetic.

[Gary S.]

Re: DOT 5 - Is this new to anyone else?

I did talk to Ken McCormick (Lone Star) at Fall Carlisle when I picked up my rebuilt calipers. I asked about the sticker voiding the warranty if Dot 5 is used because I have used Dot 5 for years. He said he was replacing seals right and left in his calipers from Dot 5 and seems it just started happening in the last 4 years or so. He called other rebuilders and they were experiencing the same thing and again seems just in the last 4 years or so. Ken did a test of his own....tested every Dot 5 he could find on his seals. All swelled the seals. Some within a day. But there was one that did not. The brand is Cartel. I bought that brand and put in my new system. Time will tell. You can find Cartel on the web. Owner is a real pleasant, helpful guy. Oh, Ken did say Dot 5 older than 4 or 5 years did not seem to swell seals.

[Duke W.]

Re: DOT 5 - Is this new to anyone else?

When you see the word "synthetic", ignore it. It's mostly marketing hype. There is no legal definition and only a vague technical definition, that is if derived from anything other than basic crude oil refining processes including distillation and catalytic cracking, it's "synthetic" because it is "synthesized" by a petrochemical process using petroleum derived feedstocks.

There are all kinds of "synthetics" that make up your vintage Corvette including polyester resin, any and all plastics, most rubber, wiring insulation, antifreeze, brake fluid, and virtually all modern lubricants have some synthetic base oils in the base stock blend

.Duke

[John H.]

Re: DOT 5 - Is this new to anyone else?

Just a note on FMVSS 116, brake fluid standard, administrated by DOT, NHTSA. The numbers 3, 4 and 5 are related to boiling temp (among other things), not composition. Just turns out that silicone and mineral based fluid exist for the highest (current) boiling point, 500 deg F. When setting standards the government tried to be technology neutral and allows competition to develop the best products that will meet the minimum spec.

Here is the spec for FMVSS 116 ( ref: https://ecfr.io/Title-49/se49.6.571_1116 )

S5.1.1 Equilibrium reflux boiling point (ERBP). When brake fluid is tested according to S6.1, the ERBP shall not be less than the following value for the grade indicated:

[Don A.]

Re: DOT 5 - Is this new to anyone else?

Well, I for one can attest to the problem using DOT 5 fluid in my 65 that I just did a frame-off on. The calipers were all rebuilt by Lonestar (with o-ring piston seals) and one started leaking immediately after bleeding. They agreed to fix under warranty but that was when I was told that if I used silicone, that I would be on my own going forward. That was last June. Now, in April my left front and right rear are leaking all over the floor. I'm going to tear it all apart and go back to DOT 4. I too have used DOT 5 in the past with zero problems other than getting all the air out. Something has changed with either the seals or the fluid formulation that would be good to know for all involved!!

[Mark M.]

Re: DOT 5 - Is this new to anyone else?

Don, what brand fluid did you use and when was it purchased? Does anyone have experience with recently bought SSBC dot 5 which is still available and appears the same as the old stock I have. I feel an understanding of this safety issue needs to be shared asap as anyone else who has pressed a brake pedal to feel it sink away.

[Joe L.]

Re: DOT 5 - Is this new to anyone else?

Just a note on FMVSS 116, brake fluid standard, administrated by DOT, NHTSA. The numbers 3, 4 and 5 are related to boiling temp (among other things), not composition. Just turns out that silicone and mineral based fluid exist for the highest (current) boiling point, 500 deg F. When setting standards the government tried to be technology neutral and allows competition to develop the best products that will meet the minimum spec.

Here is the spec for FMVSS 116 ( ref: https://ecfr.io/Title-49/se49.6.571_1116 )

S5.1.1 Equilibrium reflux boiling point (ERBP). When brake fluid is tested according to S6.1, the ERBP shall not be less than the following value for the grade indicated:

John-----


The federal motor vehicle safety standard covers FAR more than just boiling points. Related to this matter, it covers the requirements for non degradation of brake system seals and rubber parts.

I still do not understand how any brake fluid could meet the federal safety standards and cause the problems some have described above. This assumes, of course, that the elastomeric components of the brake system also meet applicable federal motor vehicle safety standards.

[Donald H.]

Re: DOT 5 - Is this new to anyone else?

Since I started this thread, I owe and update.

On my 67, I did end up using Dot 5 fluid. I installed new brake lines, took the master cylinder apart and cleaned thoroughly with denatured alcohol. Rebuilt all calipers after thorough cleaning with alcohol, used new lip seals. I only have about 200 miles on the car since I finished, but so far no leaks. I used my Motive power bleeder at a low pressure and had no issues bleeding.

Braking seems fine with nice firm pedal.

[Don A.]

Re: DOT 5 - Is this new to anyone else?

To answer Mark Mead, I do not know what brand or how old the fluid was because I borrowed a pressure bleeder from a shop that restores Corvettes and uses silicone exclusively.
I will real interested in how Don Harris's job on his '67 works out. I started with all new lines and rebuilt calipers and master from Lone Star. I thought mine was going to be OK as well but after ~ 6 months of setting, I have two badly leaking calipers.

[Mathew S.]

[Donald H.]

Re: DOT 5 - Is this new to anyone else?

Pictured is what I used. It is Made in the USA and says it meets the specification on the label including MIL-PRF-46176B for whatever that is worth.

[Gary S.]

Re: DOT 5 - Is this new to anyone else?

Regarding my post #39 and "time will tell," I just checked my calipers and there are no leaks. I had my original 66 calipers rebuilt by Lone Star with the double "O" ring system. I installed them last November and they have sat all winter. I pressure bled with new lines and new master cylinder. The Cartel silicone manufacturer told me their formula has been the same at least 10 years. Lone Star owner Ken McCormick's conversation with me indicates he believes what is in post #47 for the most part.

[Ed D.]

Re: DOT 5 - Is this new to anyone else?

FWIW, I was in a auto repair shop that services all the US Mail Trucks for a Township in NJ. There was a big sign under the hood which said DOT 5 Only. I asked the owner of the shop was this a sign put on by the Post Office or did he decide to use DOT 5 in the trucks. He said it was a long time requirement of the USPS. He said they had no problems with DOT 5
Ed

[Donald H.]

Re: DOT 5 - Is this new to anyone else?

Here's the picture I meant to post in #48.