Clutch master cylinder?

[GJO]

I had a problem at the end of last year, with my older MGF, that I originally and wrongly diagnosed as a seized clutch release arm. Bleeding the clutch seemed to cure the problem but after being off the road for a while I went to start the car and found that the clutch pedal went straight to the floor with minimal resistance. The master cylinder reservoir was drained.
So where could the fluid have gone? Because the pipe connects to the top of the cylinder, I am thinking that it can only have leaked out of the master cylinder itself. The pedal was damp with what I presume to have been hydraulic fluid.

I have removed the master cylinder (which was new less than two years ago) and dismantled it. The inside of the dust cover or boot was also wet with fluid and the outer edge of the lower piston seal has several small erosions on it - in appearance it reminds me of a spent airgun pellet which bears the scars of barrel rifling. The bore of the cylinder looks good, so I am wondering if the 'new' AP master cylinder could have been old stock and the seal has just perished? Old rubber tyres often crack up in the same way.

I have ordered a replacement master cylinder but would it make more sense to fit new seals?

[RobboMC]

I once rebuilt a master cylinder on a Toyota. They can be very fiddly to build and the small seals are easily damaged.
Was it a genuine part or an aftermarket one?

Most mechanics don't bother as it's faster to just fit a new one.
By all means build one up yourself, you just need to be scrupulously clean and careful and patient.
Oh and get some latex gloves, brake fluid damages your skin.

By the way, can you explain why you have 2 cars?

[GJO]

<snipped>
By the way, can you explain why you have 2 cars?

I like MGFs

[Green Squirrel]

I had this BUT it was the slave cylinder that was at fault.

[GJO]

Just an update - having replaced the clutch master cylinder all seems as well as it can be and the clutch release arm operates nicely so cannot be seized.

I have dis-assembled the master cylinder that I took off and the seals appear to be shot - as can be seen from the close-up image below which shows one of the seals. This is from a Clutch Master Cylinder that I fitted two years ago having purchased it "brand new" from a trusted supplier. The lesson learned is that many MGF/TF spares are no longer "brand new" and may have been in storage for ten years or more. In future I will always obtain and fit new seals - the cylinder bore is 0.625" and the seals are probably common to a wide range of vehicles . . .

[talkingcars]

By the way, can you explain why you have 2 cars?

Until Christmas I had a TF135, a mk1 VVC and a mk1 1.8i, now down to just the mk1's.

[GJO]

Just worth adding that when bleeding the master cylinder it is a sensible precaution to wear protective eye glasses. I managed to shower myself with fluid!