MX5 Clutch Master/Slave Cylinders

[sleepyhead]

Problem:
Pedal will go very light if driven for a given length of time without changing gears. Pedal regains firmness when pumped vigorously.

First diagnosis:
Clutch Slave Cylinder.

Result:
Slave cylinder is NOT leaking. Bled air out of system. Pedal still soft.

Inspection:
Investigated master cylinder and found brake fluid to be very murky.

Question:
What could have made the brake fuild murky when it's a sealed system? Could the Master cylinder be at fault? There are no leaks as the level remained the same.

Net result:
I may not be able to go visit my mum for mother's day.

[Howard]

It's possible if some moisture has got in somehow but it's hard to say. Tried replacing the fluid and re-bleeding?

[sleepyhead]

We wanted to drain it tonight but the weather is very windy.

Unforuntaley the car mechanic mate is not available the weekend I don't trust the local garages up here either.

Last time I bled the clutch system I sucessfully locked it with a load of air and bust a seal!

The pedal is back to how it was but I will find out tomorrow if it stays like that or if it goes soft over time again.

Any and all suggestions are welcome. I really can't think straight, really annoyed.

[filbert]

I don't know about the mx5 specifically, but I've not known a sealed clutch hydraulic
system, that's why brake fluid should be changed every 2 years.
It does sound like the master cylinder faulty.

[dave87]

If the brake fluid has water in it, then as the brakes heat it, it expands, allowing greater travel with no stopping power. I'd try changing the brake fluid before you replace either the master or slave cylinders.

[SilentDeath]

In my car, no idea about mx5's... the clutch and brakes are seperate systems, the only thing they share is the resevoir.

Yours sounds like the master cylinder, with a small leak sucking air in. no idea how sucsessfull they are but you can buy seal kits to rebuild it.

When I bled mine the brakes looked like almost new fluid, however the clutch slave had a huge amount of particles in it. I left the fluid to settle for a week and the bottom inch was almost solid particles

If you are pressure bleeding it, make sure you have somone push the pedal down, pump it several times to help bleed, and then keep it pressed untill finnished.


no idea whats causing it, but occaisonally my clutch pedal decideds to stay down a little, and then spings back into my foot when Im not expecting it.
I have a new clutch and slave ready to go in though.

[sleepyhead]

Brake and clutch have separate systems and reservoirs.

I'm sayign sod it, already ordered a replacement master cylinder, already have a replacement slave and plenty of brake/clutch fluid.

Drain, replace units and see what happens. With MOT close by and Nephews 4th birthday, I need the car to get around.