WARNING - DOT 5.1 Brake Fluid

[TheBuggyman]

Re: RE: Re: RE: WARNING - DOT 5.1 Brake Fluid

I am going to use the coke idea and run the vent line into the cab like a straw.

My five ton has a vent tube on top of the master cylinder, is that where you hook up the straw?

 

[JDToumanian]

Personally I like and use DOT 3, cheaper, always available and can handle water.

I agree with Bjorn here, I switched my truck to DOT 3 (Actually, the brakes were drained when I got it). But now 4/6 of my wheel cylinders are leaking, and it seems like more than just a coincidence. After I rebuild them I will still use DOT 3. I'm cheap and I don't see the advantage.

Jon

 

[1956_4x4]

Re: RE: WARNING - DOT 5.1 Brake Fluid

We found that it would take a while for the fluid to start to gel when mixed, but it would gel.

Any idea how long this would take? I wanna investigate this closely, and in a controlled enviroment.

Thanks for the input.

David

I think the earliest we were able to verify was around 3 months. We also had a few that we were not able to identify a time frame for any added fluid. I wrote these off as not having fluid additions documented by the mechanics or fluid being added by the operator. Each of these incidents resulted in a complete flush and all seals being replaced.

Smitty

 

[cranetruck]

RE: Re: RE: WARNING - DOT 5.1 Brake Fluid

FWIW, I had DOT 5 and DOT 3 mixed in an uncovered jar sitting on a work bench for about a year and they were still two distinct layers when I discarded the sample....

 

[TheBuggyman]

Personally I like and use DOT 3, cheaper, always available and can handle water.

I agree with Bjorn here, I switched my truck to DOT 3 (Actually, the brakes were drained when I got it). But now 4/6 of my wheel cylinders are leaking, and it seems like more than just a coincidence. After I rebuild them I will still use DOT 3. I'm cheap and I don't see the advantage.

Jon

Ditto on that. I switched to DOT3 too. How many 30 to 50 year old Chevrolets are still out running around on the original components? Wheel cylinders will wear out regardless of the fluid used. Is DOT5's characteristic of not being hygroscopic a benefit? Absolutely! Just seems to me that this is another case of our government being sold the latest and greatest and unless you are in an Arctic environment it is just not needed. Perhaps having the short notice need and ability to place a vehicle into such a situation necessitated the DOT5 fluid. Thoughts?

 

[1956_4x4]

Re: RE: Re: RE: WARNING - DOT 5.1 Brake Fluid

FWIW, I had DOT 5 and DOT 3 mixed in an uncovered jar sitting on a work bench for about a year and they were still two distinct layers when I discarded the sample....

That would make sense because the fluid is not being mixed. I'd guess it is being mixed under pressure while in a brake system.

Smitty

 

[wpzimmer]

Years ago we switched all of our bomb trailers from DOT 3 to DOT 5. A lot of them sat stacked in outside storage unless we had a surge to sopport. With the DOT 3 we had a high incidence of rust siezed wheel cylinders and damaged master cylinder and wheel cylinder seals. We replaced some of the seals due to wear and damage concerns but simply flushed the systems and reused the seals that appeared to be OK. Incidence of rust dropped to zero but we found out that alot of the seals that we reused seemed to shrink a bit when in service with DOT 5 awhile and began to leak.There was some information from the supply people looking into this that suggested that DOT 3 swells seals slightly and that they take a set in use. The switch to DOT 5 caused the residue from the DOT 3 to leach out of the seals causing them to shrink slightly and leak. We replaced them all with new seals and had no further problems. Really eliminated our rust problems during storage. I guess the lesson we learned is that if you are going to do fluid changes, replace/rebuild the affected parts. It's cheap and prevents future problems.

As for mixing fluids. They say you can but they are mutually insoluable. We always flushed our systems during changeover so I can't say if there might be a problem. I have had waste fluid stored for years and the two types never mix although the color of the DOT 5 seems to wash out in the presence of DOT 3.

 

[houdel]

Well, let me add my tale of woe, which might support wpzimmer's story about DOT3 swelling brake seals and DOT 5 on top of DOT 3 causing them to leak.

When I picked up my Deuce last February, I of course checked the level of the fluid in the master cylinder. It was a tad low and a very clear, light amber color. Having spent many years working on older cars I noticed after a few years the brake fluid would eventually turn a murky dark color, I assume from the absorbed water. Since my brake fluid was perfectly clear, and I guessed it was last replaced when the truck was rebuilt at Toelle in 1989, I assumed what I had was DOT 5 in my system. I topped the MC off with about 1/2 pint of new DOT 5 fluid, hardly noticing that the new fluid was purple in color.

A few days ago I noticed my brakes were getting a little spongy. I checked the MC, it was a little low again so I poured the remaining 1/2 pint of DOT 5 in the MC and my brakes were back to normal, then went looking for some more DOT 5 fluid, which is what got this whole thread started.

Yesterday I went for a little trip and parked the truck in a paved lot. When I came back, there was a puddle of brake fluid under the MC! So, is this just a normal your-MC-is-tired-and-needs-rebuilding thing, or did I mix DOT 3 and DOT 5 and cause the leak as wpzimmer described?

Next, how do I fix the thing? I don't see a MC rebuild kit listed in the X-reference list, Saturn wants $125 for a new MC but doesn't list a MC rebuild kit. Anyone have a part number for a civilian rebuilt kit for a Deuce MC, or a source for a military rebuild kit?