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Clutch master cylinder problem?
Charlie C - 22/3/19 at 10:56 AM

I’ve a problem with my clutch and I think its the master cylinder but would like your opinions and/or advice as there is a vast pool of knowledge and experience on here.

The engine and box are mk1 mx5 1.6 the clutch is a new 1.8 light weight fly wheel and performance clutch, with hydraulic actuation. The slave cylinder is a new standard mx5 item and the master cylinder is an OBP item with remote reservoir.

The systems are:
After bleeding clutch cylinders there is more than desirable pedal movement which goes away after 5-10 pumps on the pedal, after which the slave cylinder reaches maximum extension before the pedal bottoms out. If left standing for some time this has to be repeated

Start driving gear change is ok and get steady worst for about 3 miles to the point gear selection is near on impossible but I can just disengage the clutch enough to stop the engine stalling.

This was first notice of the rolling road when the clutch started dragging the push rod was adjust and the clutch pedal pump a few times to test but on the next run the clutch start slipping. I think the slipping was caused by the master cylinder being to big 1” and pumping to much fluid in to the slave cylinder, I have a 0.75” master cylinder which a can try.

The master cylinder and slave cylinder do not show any signs of leaking, I’ve checked under the dust seals and both are dry.

My conclusion is that some crud has got into the master cylinder and fluid is leaking from the high-pressure side back to the low-pressure side. In driving conditions, the peddle is not moving back enough for the master cylinder to top up the high-pressure side so getting worse the more I drive.
I have tried pumping the clutch when driving but it didn’t help.

My plan is to replace the clutch hydraulic system I’ve got a new spare master cylinder, ordered a new slave cylinder and hydraulic hose. Also the current hose has a bow’s up a lot higher than the cylinders which does help with bleeding the new one will bow horizontally)