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MG MGF Technical - Clutch problem?

As I was de-clutching last night just drawing up at home (fortunately!) the clutch pedal 'jumped' and hit the floor. (It felt exactly like a clutch cable snapping). P reg VVC was stuck in gear with the clutch semi-engaged and I had to switch off quickly. Quick look over confirmed clutch pedal was stuck (didn't pull too hard) about an inch off the floor so I duly called the RAC to give then a bit of a challenge.
RAC turned up about 45 mins later to find everything A OK! All works and feels like normal. Confirmed no leaks or apparent problems with the clutch cylinders etc. Driven about 15 miles in light traffic since.
Ideas / suggestions anyone?
Jon Francis

Two aspects here, 1 the reason for the sudden loss of pedal pressure and 2, why didn't the pedal return to it's rest position.

1, this could be an indication of low fluid level in the reservoir, but I would expect this to have been checked by RAC. This then points towards a loss of internal sealing action within the master cylinder. This may be due to ingress of a little dirt which is able to lift the sealing edge of the main seal and thus allow all pressure already built up to escape back into the resevoir. Additionally the foot pressure will slam the pedal to the floor as all the remaining fluid in front of the piston will simply be displaced via this 'internal leak'.

2, follows on from 1 in that the sudden extra force pushing the pedal into the carpet will have jammed it there. Ovcer the following minuted waiting for the RAC the pedal return spring slowly overcame the jammed pedal and returned it to it's norma position. In doing so the offending dirt was displaced and the operation of the seal return to normal.

I suggest that it is worth considering bleeding the clutch hydraulic system and if the problem re-occurs then several rapid operations of the pedal (pull it back by hand if needed) will restore operation. Under these circumstances though re-occurance indicates the need for new seals on the master cylinder or new cylinder whichever isd the preferred route. Seals are cheaper, if more work to fit!

A couple of additional thoughts are to check that the master cyl cap vent hole isn't blocked and check the pedal return spring is not broken, although this is usually very obvious in a floppy pedal above the normal pedal pressure start point.

Master cylinders are found under part number GMG 901080
seal kits are found under part number GRK 3006 and new caps are found under part AUU 8240

Rog
Roger Parker

Thank you!
Jonathan Francis

In addition to Rog's comments the bearing pivots for the clutch/brake pedals can seize up due to water ingress ,it is adviseable to give the pedals a squirt of your favorite penetrating lube eg WD40 or similar every 5k and work the pedals at the same time, this also stops any iritating squeaks, HTH.
Mike.
Mike

This thread was discussed on 06/12/2001

MG MGF Technical index

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