Brake fluid mix up
 

About 4 years ago I got some "Motul" Dot 4 brake fruid from PFS. I was told to just add it after I changed my brake lines. I did a pretty good flush, but did not rebuild my calipers. I just read that it is synthetic and is not compatable w/ mineral based fluids (stock Mazda DOT3). That was 4 years ago and the only problem I've had was that the first press on the pedal is sometimes a bit soft, but the 2nd press is tight and stops great. Any thoughts on this matter? I thought the incompatable fluids would have caused many more problems by now.

That first soft press is due to incomplete bleeding. The first press should be as firm as it gets if it was all done right.

When was the last time you changed your brake fluid. Motul usually needs to be changed at least once a year (which is why more people use Super Blue instead).

911,
Not necessarily true.

I'll forget the details and just provide a url on pad knockback:

http://www.stoptech.com/whitepapers/knockback.htm

To test this:

Drive car in straight line, double-tap brakes to verify firm pedal on second application.
Directly following this, (do not change direction of front tires or steering!) accelerate and brake in a straight line seeing if brake pedal on first press is as firm as it was on previous stop second-press.

Also the issue is not that it is synthetic or not - but more so if it is silicone-based or not (DOT 5 = no-no, DOT 5.1 = ok). Motul DOT-4 and 5.1 fluids are not silicone-based.

Very interesting. Thanks for the info clayne.

where do you get the super blue?

thanks majik. i also found it in the summitt racing catalog. Man i swear you are better than the search button :)

We're going to have to tell noobs to use the Mahjik instead. :p:

Oops, haven't changed fluid in 3 years. MIght switch over to Super Blue and do a complete bleed. Thanks.