It was suggested that I run DOT 5 brake fluid to avoid the mess and lifted paint you see around the master cylinders for the brake and clutch. I am repainting my firewall and DOT 5 fluid will not ruin the new paint.

Given that our systems are vented and therefore there will always be some brake fluid around that area that seems a good idea. However the local parts house did not carry any DOT 5 fluid, and acted like I was nuts to want it.

I looked it up on the Internet and found that it was not recommended for ABS, and that there were two problems with it.

One is that it does not absorb water so any water that collects in the brake system will migrate to the lowest point (wheel cylinder) and, unless purged on a regular basis, remain a slug a pure water. This could cause the cylinder to corrode, or worse, flash to steam in the heat caused by hard braking.

I should also point out that water contamination is the same with DOT 3 and 4 fluid, except that they absorb the water. This lowers the boiling point of the brake fluid, and will cause some additional corrosion and wear, but is not a big problem. I didn't know it, but most companies recommend that you drain and refill your brake system every few years to remove the water trapped by the fluid.

The second problem had to do with trapped air in the system. DOT 5 tends to trap microscopic air bubbles, producing a noticeable spongy feel to the pedal. This is why it is not recommended for ABS.

Frankly, in reading what was written I wonder if people are making mountains out of mole hills - that is, making a big deal out of a minor imperfection.

Is anyone running DOT 5 fluid in a stock setup, and have you had any problems with water contamination or spongy feeling brakes?

 

Racers use DOT5 (silicone) all the time without problems. Just don't try to mix it with any other type they are not compatable. System needs to be completely flushed of any old fluid. Be especially careful should you take it to one of the quick oil change places that they don't do you a "service" by topping off the MC.
PS: go to a speed shop or store that caters to road racers or possibly motorcycle shop for DOT5.

 

I have used it and will use it in my 48 F-3 but it is not a stock brake system. I have had no problems with it. I have heard that it can cause a spongy pedal but I never experienced that. I did notice that my brake pedal did not return as quickly as before. NAPA and VIP both stock Dot 5.

Vern

 

I've been using it for just over 2 years now with no problems. From what I understand DOT 5 was developed for the vintage vehicle market. As far as water being a problem I kind of doubt it. How many of us have done the honing or replacing the brake and master cylinder thing using the DOT 3 because of rust from water? I can't see how DOT 5 could be any worse. Maybe flush it out every few years to be absolutely sure but I'm not worried too much about it.

 

Doesn't Dot 5 supposed to absorb air more that Dot 3 and is harder to get it out?

 

Yes ------- but is that a real problem? don't think so!

 

Nathan,

I did not have a problem with that on my Mustang. The bleeding process was quite normal.

Vern

 

The problem with air is when you pour DOT 5 in the master cylinder. Thats how the air bubbles can get in the fluid, it has to be poured real slow and not allowed to splash. Same goes when bench bleeding the M/C with DOT 5.

 

I have used DOT 5 in my F100 (Volare clip)for at least 10 years. The only problem (not attributable to me) was the pedal "went away" during a very hot long drive. After things cooled down, the pedal returned. I bled the brakes and the problem went away for good. I'm not sure what caused the problem. A year or so ago, I decided to bleed the brakes again based on info that water would accumulate. My only problem with that was, one of the Volare bleeders would not reseal. (No good deed goes unpunished.) I have been satisfied with the DOT 5. The only drawbacks are it is very expensive and even more importantly, can be had to find. (Plan ahead for trips)