[Guest]

HI,
Seems I am in need of my 3rd master Cylinder. I have a 99 TJ I purchased new in Aug 98. I have 31,000 miles... Now that all that is out of the way...

About 1.5 years ago my Master cylinder went bad. it started getting spongy, when you removed the fill cover the rubber gasket was swelled up and spongy. I put a new (bad) master cylinder on and could not get any pedal. I took it to a local shop (no jeep warranty to old) they found the master cylinder to be bad, an since I purchased it at the local NAPA they we given a replacement at no cost.

The replacement has worked for the last 1.5 years until last weekend, I went to move the jeep and the same spongy pedal I had before was back. I removed the fill cap and again it is so swelled up I almost could not get it back into the reservoir.

Any ideas? I do not drive it much. Could this be the problem? Or is it the fluid causing the rubber to "go bad"

Thanks

Erik

 

[ecamp55]

Sounds like somehow you havea mix of 2 different fluids in the system. I know that once a certain fluid has touched a rubber seal, you don't want to use a different type (even if you clean out the system). It will make the seals get spongy and swell just as you described. FWI, I think that the DOT5 fluid is compatible with all seals these days.....but expensive.

 

[Guest]

So... DOT3 can't be mixed with DOT4?

 

[ecamp55]

Nope, not the way I've been told. I've "heard" that you can mix DOT5 with DOT3 or DOT4 but, I've always been to chicken to try it.
And BTW, before someone else says it, please fill out your profile....it only takes a minute and it helps us help you.

 

[mav750]

It sounds to me like you have had oil or some other petroleum based product added to the brake fluid. I would check the fluid for contamination, there are test kits that you can get at a parts house. If that is the case then all the rubber parts of the brake system are also swelling and will cause headaches. If that isnt the case, put a new master cyl on, and bleed the heck out of the system till you have replaced all the old fluid with new. Good luck.