Clutch hydraulics issue

[Rich_NYS]

This past Winter I replaced the clutch slave, rebuilt the master, and pressure-bled the system. It has a braided steel line.

Everything has been working perfectly, then the pedal went straight to the floor....felt like the line was cut.

-Zero resistance in the pedal.
-No leaks.
-Fluid in the reservoir is at the proper level
-Fluid rises in the reservoir when the pedal is pushed.


I'm thinking it's the MS....any suggestions on further troubleshooting before I take things apart?

Thanks!

[PJ Grady Inc.]

This past Winter I replaced the clutch slave, rebuilt the master, and pressure-bled the system. It has a braided steel line.

Everything has been working perfectly, then the pedal went straight to the floor....felt like the line was cut.

-Zero resistance in the pedal.
-No leaks.
-Fluid in the reservoir is at the proper level
-Fluid rises in the reservoir when the pedal is pushed.


I'm thinking it's the MS....any suggestions on further troubleshooting before I take things apart?

Thanks!
Sure sounds like a leaking reservoir seal. Pull the clutch MC reservoir cap off and apply the clutch...gently. If fluid shoots upward from the reservoir you have successfully diagnosed the problem. If there is no fluid movement perhaps the clutch master inner pushrod has become disconnected. Obviously you should clean any spillage.
Rob

[Ron]

Plug the MC outlet and see if the pedal gets hard as a rock...

[Rich_NYS]

I pulled the MS, I didn't see any issues with it and I had pressure when pushing the piston.

I put a new piston in it and reinstalled it. I haven't bled it yet, but the pedal feels the same.

[Rich_NYS]

I bled the system and it seems to be OK now. I haven't driven it but now the clutch fork moves when the pedal is pressed.

I'm really baffled as to how air got into the system without a fluid leak, and how/why the symptom appeared so suddenly (felt like the line was cut.)

[David T]

If air should get into the system it is no longer hydraulic, it is pneumatic. Any pressure no longer pushes on the slave cylinder, instead it just squeezes the air. Could have been an air bubble in the hose connecting the reservoir to the clutch master cylinder. Check that hose. If it is cracked or "sweating" it should be replaced.

[DMCMW Dave]

When you replaced the slave, what did you use for a seal where the adapter joins the slave? OEM is a plastic seal, and I've seen a couple that would not leak but would somehow let air in. That should be replaced with a copper washer.

Otherwise, I'd agree that you have something gone wrong in the master. The master can leak internally, but a bad slave will leak on to the ground. If the master is bad, a good test is to take the cap off and press the pedal. If fluid comes up out of the filler hole, it's bad internally.

[Rich_NYS]

When you replaced the slave, what did you use for a seal where the adapter joins the slave? OEM is a plastic seal, and I've seen a couple that would not leak but would somehow let air in. That should be replaced with a copper washer.

Otherwise, I'd agree that you have something gone wrong in the master. The master can leak internally, but a bad slave will leak on to the ground. If the master is bad, a good test is to take the cap off and press the pedal. If fluid comes up out of the filler hole, it's bad internally.

I think it was a copper washer but I'll need to check to be sure.

Before I changed anything, I checked and could see the fluid rising in the reservoir. I replaced the piston/seal/spring thing and will test drive tonight.