DC5R Clutch Pedal Sinking

[ChargeR]

What do you guys think? Is it possible for the CMC to leak internally randomly like this?

It's possible for the DC5 CMC to leak internally, a friend had a similar issue as you and I initially discounted the CMC as it wasn't visibly leaking. It proved to be the culprit though, and I suspect it is in your case too.

[butter]

It's possible for the DC5 CMC to leak internally, a friend had a similar issue as you and I initially discounted the CMC as it wasn't visibly leaking. It proved to be the culprit though, and I suspect it is in your case too.

How do you identify if it is leaking internally? Also, where exactly can it leak internally?

[sleepingperformance]

When you look at the clutch master cylinder there is the square plate on the side. What will happen is the front seal of the cylinder is not holding pressure and fluid builds up in that area. As it is externally sealed and the rear seal is still good, the is where the fluid will build up

[ChargeR]

How do you identify if it is leaking internally? Also, where exactly can it leak internally?

Thread revival, but this question bugged me so I took the master cylinder that you kindly gave me apart to confirm my suspicions. Here's the triangular damper section that often gives people trouble, the bolts or the actual threaded section of the master cylinder casting fail as in this case with the subsequent loss of fluid and no clutch pressure to disengage the clutch.



The other way for the master cylinder to fail is for one or both of the seals on the piston to fail and allow fluid past, by failure of the seal itself or damage to the cylinder bore. The piston that gets pushed in when you push the clutch has two seals and two sections, the first (1) on the left of the picture below is what actually displaces the fluid and thus moves the slave cylinder and disengages the clutch when the pedal is pressed. The second part of the piston (2) is just a seal to keep the fluid in, because when the master cylinder is pushed in seal (1) passes the inlet hole where fluid comes in from the reservoir. The quick sketch I made below illustrates it more clearly.






So seal (1) in the above pictures can fail, and leak under pressure applied from the slave end by the clutch pressure plate spring, and the fluid leaks past it back into the reservoir. There's no external leakage or sign of failure.

[eLtrix]

Quite interesting read tom