Broken Clutch Master Cylinder

[eddyy]

I tried searching but didn't find anyone else that posted about this issue.

When I pulled my car out of the driveway I pressed the clutch down and heard a loud "pop". Immediately after hearing the noise I lost all pressure on the clutch pedal. It just moved back and forth freely with no resistance either way.

After calling into work and having my girlfriend help me push my car back up my driveway I noticed I had no fluid in the clutch master cylinder reservoir so I filled it back up to the "max" line. I regained pressure on the clutch but lost it again after only a few pumps of the pedal. That's when I noticed a puddle of fluid on the top of my transmission. So I added only a little more fluid into the reservoir and had my girlfriend pump it a few times while I looked at the area.

Sure enough a geiser of brake fluid would spew out from underneath the master cylinder. So I took it apart but didn't find any obvious signs of damage. The black o-ring was fine, there was no corrosion, and the ring lock was securely in place. It was only when I was cleaning the parts to reassemble it that I noticed the metal disk that is sandwiched between the o-ring, a metal washer had a crack on it.

I could not find this disk for sale anywhere on the internet, I even called my local dealer to find a part number for it but they only sell the clutch master cylinder as a unit.

How could a metal disk like this just crack under normal use? Have any of you had a similar failure?

Due to this 60 cent piece of steel I now have to pay $160 to get a new one sent to me... FML

*note I colored the steel with dye to make the crack visible.

[Tcoat]

Have never seen this mentioned before. Stock clutch?

[Fred E]

Originally Posted by Tcoat

Have never seen this mentioned before. Stock clutch?

Yeah, this is certainly a new one... I'd love to see a dealer try and say this is a wear and tear item and not cover it under warranty. I feel that would be a hard sell even with a heavier aftermarket clutch as people even use twin discs with the stock master without this happening (as far as we know, anyway).

[Ultramaroon]

I've wondered what that thing is underneath the cylinder. Are those the only parts? Can you show how they stack together? Nice job with the dye, btw.


I will guess that you are running bone stock. Next, I will guess that your TOB has been binding on the quill.


So my final guess is that, for whatever reason the diaphragm exists, when you stepped on the clutch, this time instead of the fork breaking, the diaphragm popped.


Guesses upon guesses because I really don't know why that thing exists.

[eddyy]

Originally Posted by Tcoat

Have never seen this mentioned before. Stock clutch?

No, Competition Clutch Stage 3 Clutch.

Originally Posted by Ultramaroon

I've wondered what that thing is underneath the cylinder. Are those the only parts? Can you show how they stack together? Nice job with the dye, btw.


I will guess that you are running bone stock. Next, I will guess that your TOB has been binding on the quill.


So my final guess is that, for whatever reason the diaphragm exists, when you stepped on the clutch, this time instead of the fork breaking, the diaphragm popped.


Guesses upon guesses because I really don't know why that thing exists.

I already scrapped the old MC, but it goes like this:

1. O-ring
2. The disk that broke
3. Metal ring/washer (you can see it to the right if the broken disk)
4. Another, larger metal disk
5. Spring lock(idk what it’s called)


As for warranty, unfortunately my car is at 70k miles so I’m out of the standard drivetrain warranty

[Ultramaroon]

In the OP, you asked how this would happen under normal use. It wouldn't. Don't blame the stock master cylinder.


You could've probably just plugged the orifice and kept using it.

[Tcoat]

Originally Posted by eddyy

No, Competition Clutch Stage 3 Clutch.





I already scrapped the old MC, but it goes like this:

1. O-ring
2. The disk that broke
3. Metal ring/washer (you can see it to the right if the broken disk)
4. Another, larger metal disk
5. Spring lock(idk what it’s called)


As for warranty, unfortunately my car is at 70k miles so I’m out of the standard drivetrain warranty

Wouldn't be warranty work anyway. You modified a part of the car beyond the design specs of the supporting system and it broke. Simple.