Topic: Brake Fluid - What are you guys using...

[Morsel]

So I sent out my master cylinder to be rebuilt and re-sleeved by White Post, despite all the comments about them, they did a fine job, it looks really good. The only thing that surprised me is they said they will not guarantee their work if you use Dot 5 brake fluid because of the breakdown of the rubber seals. But then I had Jim Cowles do my calipers and he said to ONLY use Dot 5 (which I know is because of these classic and basically Dot 3 and 4 are like paint remover), and he used it while rebuilding my calipers, so they are filled with Dot 5.

I was planning originally on using Dot 5, but the little note freaked me out. My car is sweet and I drive it, and sometimes drive it hard, don't want any brake problems.

So what would you all do, ignore White Post or Jim Cowles, it seems like a pretty obvious question based on both their reputations and the fact that Jim Cowels is doing HiPo cars, but I'm curious what others are doing and using.

Thanks,

Jason 

[67gta289]

I’ve used dot 5 since 1981 are have had zero issues.

[preaction]

Used since 2003 and going strong without issue. Also there is no need to flush or replace the fluid every 3 years as should be done for a car that sees limited use with dot 3 or 4 fluid.

[Bob Gaines]

So I sent out my master cylinder to be rebuilt and re-sleeved by White Post, despite all the comments about them, they did a fine job, it looks really good. The only thing that surprised me is they said they will not guarantee their work if you use Dot 5 brake fluid because of the breakdown of the rubber seals. But then I had Jim Cowles do my calipers and he said to ONLY use Dot 5 (which I know is because of these classic and basically Dot 3 and 4 are like paint remover), and he used it while rebuilding my calipers, so they are filled with Dot 5.

I was planning originally on using Dot 5, but the little note freaked me out. My car is sweet and I drive it, and sometimes drive it hard, don't want any brake problems.

So what would you all do, ignore White Post or Jim Cowles, it seems like a pretty obvious question based on both their reputations and the fact that Jim Cowels is doing HiPo cars, but I'm curious what others are doing and using.

Thanks,

Jason

A important question to be considered before answering is how you intend to drive the car. Do you plan to do open track or street/pleasure driving?

[Morsel]

A important question to be considered before answering is how you intend to drive the car. Do you plan to do open track or street/pleasure driving?

Plan on mostly cruising, going to car shows and an occasional “what can this K-Code do” Put probably 200 to 300 miles a year on it.

Jason

[Building 3]

I have used DOT 3 in my older and classic cars.  I use the brake strip testers each year to see if there's any deterioration. Never seen any deterioration, but I still change the fluid every 5-6 years. The cars only get 300-700 miles or so a year and are in a heated garage. No track time.  For my daily drivers I change the fluid every two years.

[Bob Gaines]

Plan on mostly cruising, going to car shows and an occasional “what can this K-Code do” Put probably 200 to 300 miles a year on it.

Jason

I and others have used the Dot 5 for years in the vehicles that do not get used as much as a daily driver because the fluid is more maintenance friendly. The fact that the silicone does not absorb water into the system keeps the brake calipers and wheel cylinders ,proportioning valve etc. from freezing up internally from rust . Regular brake fluid absorbs water faster and must be changed frequently to keep rust from forming on the internal metal surfaces. Another plus is if or when it break fluid leaks somewhere it will not eat the paint  . The Dot 5 is not good if you are doing open track with the car. I don't use Dot 5 in any car that I would vintage race. Those type use vehicles should have brake fluid flushed every 6 months or so.  Dot 5 has a lower boiling point and gives a softer pedal feel. Given your driving habits and expectations and it sounds like the dot 5 would be what I would suggest using.   

[1966KGT]

+1 Dot 5, had it in my cars for decades, no track use, no issues.

[Morsel]

Well, it's sounding like everyone is happy using the Dot 5 and with it being overall a safer alternative I'm probably going that way. I'm doing all new lines anyway to the back of the car, new restored rear end, the front lines and proportion valves have already been cleaned out, and have new front calipers with Dot 5 used to assemble, sounds like I'm good to go.

Thanks everyone for giving your insight on this, very helpful.

Jason

[NEFaurora]

DOT 5 seems to be harder to bleed for some reason (Harder to get rid of the air bubbles)..

)

Tony K.

[midlife]

DOT 5 seems to be harder to bleed for some reason (Harder to get rid of the air bubbles)..

  )

Tony K.

Yes, whatever you do, do not shake the can of DOT 5!
I wonder why White Post refused to warranty their work with DOT 5?  Never had a problem with seals...

[Morsel]

Yes, whatever you do, do not shake the can of DOT 5!
I wonder why White Post refused to warranty their work with DOT 5?  Never had a problem with seals...

Yeah, it kind of shocked me when I opened the box and found the disclaimer in there considering I was planning on using it. I will be very careful and let it sit for a few days in the bottle before bleeding. I'm vacuum bleeding the brakes so it should go through ok I would think...

Thanks,

Jason

[ChrisV289]

I heard if you are currently running DOT 3 and want to go to DOT 5, everything has to be changed so there is no trace of DOT 3 in the lines before adding DOT 5.  Is that true?

[midlife]

I heard if you are currently running DOT 3 and want to go to DOT 5, everything has to be changed so there is no trace of DOT 3 in the lines before adding DOT 5.  Is that true?

That's my understanding; either that or flush the system completely.

[sgl66]

I heard if you are currently running DOT 3 and want to go to DOT 5, everything has to be changed so there is no trace of DOT 3 in the lines before adding DOT 5.  Is that true?

Yes it is true, do not mix.

Also as noted previously, do not shake can prior to pouring into master cylinder as dissolved air is a known risk with silicone fluid which contributes to a soft pedal.   

More on boiling points and high altitudes as well http://www.dtic.mil/dtic/tr/fulltext/u2/a251835.pdf