Clutch Fluid type

Hey gents,

Is there a way to tell what fluid was ran in the clutch master cylinder?
or could I just run a full load through to get most of it out?
Any recommendations on which one to use?
Will the DOT4 fluid be fine? I’ve had my 2nd slave go bad now. This one only lasted 5 years with very minimal use. Or could the lack of use be causing a problem?

thanks for your time
For clarity I'm more asking whether synthetic or mineral would cause any problems. I think it may have had synthetic in it but silly me forgot to make a note of which one I used.

Bill Kearley

A flush is for sure but with what I don't know. I haven't heard about any other problems.
Others please weigh in on this!
These various "DOT" fluids have caused lots of confusion. Typically, I think the debate is between DOT 3 and 4, and a good recommendation I received was to use Valvoline Synthetic DOT 3/4. Somewhere I also read that this Valvoline Synthetic was for persons who couldn't decide between 3 and 4! As originally pointed out, lack of use of the system is probably the biggest problem contributing to the leaks.

/s/ Chris Kennedy

Bill Kearley

DOT numbers 3 - 4 and such are about wet and dry boiling points and 3 will absorb less water over time. Some after market and race reservoirs are vented, that's why I use DOT 5. The clutch area won't get as hot as breaks but it's just easy to use one type of fluid.

Howard Jones

First, if the clutch system has had silicone fluid in it you can either drain and refill with new silicone, or second, completely decontaminate the system and change to normal modern dot 3/4 synthetic brake fluid. My cars use the same fluid as the brakes in the clutch system. This keeps things simple.

A word on mixing silicone and synthetic (normal) brake fluid. All brake fluid is synthetic unless it is silicon. They cannot and should not be mixed. Decontaminating means disassembly and rebuilding the master and slave with all new seals and flushing the tubing with isopropyl alcohol.

I have been using Redline RL600 for a while now and report no issues. I pump out the old stuff each winter along with the other annual fluid changes. Engine oil, Grbx oil, coolant, and brake & clutch fluid. RL600 is a good value and the boiling point is above 400F wet and 600F dry. This is what I consider a minimum performance for a track car.

Here are couple of pages on Brake fluid specs/costs:

awesome response guys, thanks so much for your time. i ended up putting the DOT5.1 in it. havmt had a chance to properly bleed it all yet but i flushed 3/4 of a bottle through hoping it would clean any contaminants in the line.