How do you know when a master cylinder is going out/bad? Help.

[KKell83]

As some of you know I just installed a new clutch yesterday. Prior to that I was on the stock clutch and it seemed to go out pretty quick once I added on my Procharger at roughly 24k miles. Well, being the second owner to my car (got it at 20k) you're never too sure how the previous owner took care of it or if they beat it to death. Well, nevertheless, when it was NA I experienced some transmission funkyness - some days it'd shift like butter other times or even in the same day it'll fight me to go into gear; anything from cruising to spirited.

To expand on this a little more, you can come to a light (downshifting if you wish) and it was fine, hold the clutch at the light for a minute or place it in netural, when the light turns green I'd put it in gear with a little effort add accerateration and the grab point changes... instead of mid it was at the very top of its travel. I never really though much about it since I was just a new car to me. But after the Procharger -canned tune- you could feel it more and more not to mention the transmission just felt notchy so I tried a few different brand MTF or DCT and it did get better but nothing life changing, BUT on certain mornings for whatever the reason the transmission would run SUPER smooth. So much so that I'm talking about how nice it is on the way to work but by the time I jump back into it the clutch feels like sh*t again. But here's the craziest thing, when if feels bad I could "beat on it" and it goes back to feeling good - shifting smooth and proper engagement.
Obvisually with all these issues I figured my TOB was my corporate, then once I got my car retuned and started shifting at 7500 my clutch started to slip. Well BINGO! It's just a bad clutch but I'll replace everything asap, so I did!

I swapped it in a Centerforce twin disc SST clutch and billet steel flywheel. Granted, I only have 50 miles on it and installed it yesterday (8/21) but I'm not sure if my brain is playing tricks on me but the same things are happening here as they once did!!

So, as the title says, how do you know when a master clyinder is going out or bad?

Thanks,
Kenneth K.

Sponsored

 

[djcodeman]

I'd like to know as well...

It seems after a couple of hard pulls the pedal feels less stiff, but a few minutes later goes back to normal... I was assuming its just the brake fluid heating up and cooling down?

 

[17MagMetal]

Are your brakes acting up? A bad master usually equates to the internal seals going kaput and letting brake fluid behind the master cyl pistons.

In both your positions I’d completely flush brake fluid to start. Use a cheap DOT 4 and try the drives again. Well worth the $20.

 

[Snakebyte]

Are your brakes acting up? A bad master usually equates to the internal seals going kaput and letting brake fluid behind the master cyl pistons.

In both your positions I’d completely flush brake fluid to start. Use a cheap DOT 4 and try the drives again. Well worth the $20.

I think I made the same initial observation. I believe the OP is speaking of a hydraulic clutch master cylinder, not a brake master cylinder.

 

[Adam the Lighting Guy]

It could be either the clutch master cylinder, the slave cylinder or even the hose between them. You're not getting full disengagement at times it sounds like. That's why it's notchy or you have difficulty sometimes just getting into gear from a standstill.

I don't know how physically close slave cylinder is to the exhaust you have running or even if you have a clear view of the slave. If you can get under the car, look for weeping or moisture from the slave cylinder first.

How does the fluid look ??

 

[ORRadtech]

I think I made the same initial observation. I believe the OP is speaking of a hydraulic clutch master cylinder, not a brake master cylinder.

I thought some cars shared brake fluid with the clutch. IDK if that pertains to the Mustang.

My first thought was that the clutch had not been bled well.

 

[Adam the Lighting Guy]

I thought some cars shared brake fluid with the clutch. IDK if that pertains to the Mustang.

My first thought was that the clutch had not been bled well.

If that were the case, typically the "action" of.the clutch would be consistently bad without fluctuation. It's worth a shot bleeding it.

Sponsored