Best brake fluid

[Al R.]

What's the general consenus for a 67 vette being used in eastern NC on brake fluid Silicon or traditional. Car will only see limited driving each year (500-1000 miles tops)

[Harry S.]

Re: Best brake fluid

Everyone will have their own opinion on this. I drive my 63 about 1000 miles a year. The wheel cylinders needed to be replaced every two years with DOT 3, since I changed to DOT 5, the problem has gone away. But then again I live in NH.

[Joe L.]

Re: Best brake fluid

What's the general consenus for a 67 vette being used in eastern NC on brake fluid Silicon or traditional. Car will only see limited driving each year (500-1000 miles tops)

Al------


If you have the system COMPLETELY empty and free of any remnant of the glycol-ester fluid (i.e. DOT 3, 4 or 5.1), then I would go with silicone-based DOT 5 fluid. If not, then you will need to continue to use the glycol-ester fluid.

Note: if you ever spill any of the glycol ester fluid on your paint, you will completely appreciate another advantage of the silicone DOT 5 fluid.

[Al R.]

Re: Best brake fluid

Joe, it will have new lines, hoses, and MC, however some fluid is probably present in the calipers. Will this be pushed out or mixed with the silicone when bleeding the brakes. How would be the best way to completely remove the old fuild if this will be a problem?

[John F.]

Re: Best brake fluid

Flush out the old with denatured alcohol. Then use DOT-5.

[Joe L.]

Re: Best brake fluid

Joe, it will have new lines, hoses, and MC, however some fluid is probably present in the calipers. Will this be pushed out or mixed with the silicone when bleeding the brakes. How would be the best way to completely remove the old fuild if this will be a problem?

Al-----


My recommendation would be to rebuild the calipers and in doing so clean out all of the old brake fluid. It's extremely difficult to remove all the fluid with the calipers assembled and on the car. You can flush as John suggests with denatured alcohol. However, you still have to remove all of the denatured alcohol. This can be done with a vacuum pump but I still would prefer rebuilding the calipers. Caliper seals don't last forever, anyway.

[Timothy B.]

Re: Best brake fluid

When changing my 67 to dot 5 silicone fluid, I cleaned the master cylinder dry and filled with dot 5 and flushed by bleeding the brakes at all wheels until the silicone ran clear through all the caliper bleeders and to this day it's fine FWIW.

[Domenic T.]

Re: Best brake fluid

Al,
I think the guys using dot 5 with standard brakes do not like the feel of the pedal (to hard) where as the guys with power brakes don't feel the difference as much.

I like the advantages of dot 5 but do not like the way the brake pedal felt with standard brakes when I switched years ago.

I did the flush job and dried the solvent with air when I did my vette.

In my tug at the shop I put dot 5 directly over dot 3 when I desperatly needed to use it one day and the brakes have never leaked since.

I know the 2 different fluids are not to be mixed but we had dot 5 in the bleeder and someone put dot 3 in with the dot 5. So I filled the master cylinder of my tug thinking that I would be doing a complete brake job that it needed any way.

That was a few years ago and the brakes never leaked down again.

I'm not saying to mix them but only bringing up the point that if you don't get all the dot 3 out it's not the end of the world.

I would say my tug is about a 50/50 mix and has survived the long term affect that many think would happen and they never worked better in all the years we used it.

DOM

[Terry M.]

Re: Best brake fluid

The Dow Corning DOT 5 from the 1970s said on the label to simply use the DOT 5 to push out the glycol fluid until the new fluid (purple color) showed at the bleeders. A later SAE paper was the genesis of the research about the results of mixing the two types of fluid, but that paper used military vehicles (some stored for years) in Panama as its basis. One might be hard pressed to find more humid conditions than the ones that paper is based on, but I guess that was their point.

[Paul J.]

Re: Best brake fluid

Al, I've used DOT 5 in a system that was not completely flushed of DOT 3 and I've had no problems in the 25 years since I did it. This car is in central NC. If I recall correctly, the paper that Terry mentions said the study found no major issues with mixing DOT 3 and DOT 5. I believe that there was some discussion about a black sludge, but it was not very viscus and not acidic, and had no effect on the operation of the system.

DOT 5 is anhydrous, and unlike DOT 3, it will not absorb water. I also believe that DOT 5 is safer to use than DOT 3.

The next time I do this I will probably use DOT 5 to flush the system. I'm not sure that I want alcohol or some other solvent on my seals, even temporarily.

Paul