OK, I got a 4 puck and HD hub in. I have a brand new mazda clutch master and slave cylinders. I also have a SS clutch line. Since I got this in the clutch works fine when it's cold but after driving a while it gets spongy. I checked the fluid and it was black so I recplaced it with some fresh dot 3 like the cap said and bleed it out. Now it is starting to do it again and the fluid is turning dark again.

Is my fluid getting to hot from the added pressure? Will DOT 4 fix this? I was curious if dot 4 had a higher boiling point or if there is something abotu it thats bad for the system? It's all tubing or SS line.

 

DOH!! Nobody knows? Come on guru's I know someone knows this.

 

I believe you still have air in your master cylinder. Did you bench bleed the cylinder before installing. The fluid turning black so soon? Not sure about that.

good luck,

 

The slave tends to get pretty hot sitting where it does, but the fluid shouldn't get gunky THAT fast...

I've been using DOT4 forever with no problems (pretty much stock clutch, however).

Even tried DOT5 for a year (I rebuild 'em every year).

It almost sounds like the seals down in the slave are getting mushy after they heat up. I know you said the slave was new, but how long have the seals been sitting on the shelf?

Compressing the fluid in and of itself wouldn't heat it up, because brake fluid doesn't compress (that's the reason we use it, lol). Pushing it through the little orifices at 1000+ psi would, though.

Are you using the clutch at an extremely high rate (autoX, etc...)?

 

I'm using standard prestone Dot3 which I did read just now has the lowest boiling point. But you answered my question that I can run Dot4 since you have been running it. I will try that and see what happens.

Haven;t been autocrossing. It is very stiff and grabs hard so there is alot of clutch work going on in stop and go to keep it as smooth as possible.

Maybe a racing fluid would help AP550 or Motul 550.

 

Come to think of it, the DOT3 I used to use in my 1st gen was always gunking up and killing the slave seals too (that's why I rebuild 'em every year, I'm used to it, lol), so hopefully that's your only problem- you just need better fluid for your application...