Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Clutch sticking ?

My 2011 +4 Supersport has developed a knock on the clutch pedeal when i release it , there is no knock when pressing it in. On the odd occasion , usually when setting off in 1st the clutch doesnt engage until the end of the pedal but then grabs and stalls, The knock i can feel is near the end of the travel on the pedal.

Any views/ideas most welcome.

which gearbox have you got Hugo, 2011 could be the Ford MT-75 or the Mazda?

Mazda box

Do the easy stuff first Hugo. Bleed the clutch fluid. Lubricate the end of the pushrod where it passes through the release arm at the bellhousing.

Then watch the movement of the pushrod as a helper presses the clutch down and up. The action should be smooth. If there's a physical "click" it should show. It might be stiction in the slave cylindr, but a fluid change and lubrication of the pushrod is the best start.

Also check the condition of the clevis pin at the pedal. The pin is soft metal and is known to wear, sometimes drastically.

I think i have found the problem, i think it is the master cylinder, when the pedal knocks you can hear fluid going back into the reservoir,so i guess the seals have failed.
Anyone know the part number for the master cylinder,is it a Ford part £151 from Brans Hatch

All the symptoms suggest the clutch master cylinder piston or fluid is not returning smoothly. A strip and overhaul will doubtless provide the reason.

When a heavy footed gent operated mine whilst on a rolling road it was left with a lot of pedal return play although clutch action not effected. At first I suspected a broken external pedal return spring but there isn't one on my car. In any case by the end of the 50 odd mile return journey it had corrected itself. Can only assume the extraordinary travel placed on clutch pedal had left the m/cylinder return spring coils jammed temporarily. Not happened since

That's great Hugo and all the above applies.

The Mazda box has an external slave so that's better than the MT-75 which has an internal concentric item. Is the knock you describe like the peddle suddenly springing up under your foot when you are releasing the clutch peddle. If so this would indicate a mechanical issue. so everything Dave has said is spot on --the way to go!

! is it sticking/jamming on the clevis pin at the foot peddle. notoriously soft and wear unbelievably!

2 check the links and actuating rods at the master cylinder and the slave cylinder.

If all is well there then it could be wear in the slave cylinder/master cylinder or just cruddy brake fluid and or possible seal issues on the piston, one seal can degrade and cause jamming!

3 next would be to actuate the clutch using the arm which goes into the gearbox and see if it is a problem there . this would indicate something closer to the gearbox.

First check the actual slave rod to clutch release arm function, they have been known to bend. Use your hand or a piece of wood to push the release arm on the gearbox throughout its range; if that's smooth and consistent then you're in luck as the gearbox can stay where it is! Fortunately the mazca box is fitted with the slave mounted externally'
Bleeding is a simple process here and you could try that as a first option, see if there is any difference as this will help diagnosis to the master cylinder.

You might be able to get a repair kit for either master or slave cylinder if its not to far gone and when you have identified what the fitment it.

This is the master cylinder internals, the shaft has a plastic coating that has started to peel , there was bits of plastic trapped on the seals and were badly scored, the oil was also very dark

Hi Hugo,

Think you'll have to ask BHM, Melvyn Rutter Or Williams etc. as its not very clear by part no. External slave shows as part MBH0676 for left or right hand drive 06-12 M/Y

Yet it also lists MBH0675 and diagrammatically shows the external slave although doesn't mention the concentric slave of the Ford MT-75 box fitted from 06-11 M/Y.

If you have the Mazda box these were fitted by Ford, Volvo and Mazda. £151 sounds about the stupid price a Morgan fitment would be but I'm sure if you could ascertain where else its fitted the price would plummet! perhaps others will know more as you surely can't be alone here!

What's the internal barrel like? Smooth and unmarked or perhaps scratched and or stepped?

Paint or plastic coating not a great idea especially if it can fail! I must admit I have never seen that before. Dirty fluid is very common in a clutch as it holds a small volume and gets used 1000's of times more than the brakes! That micro graining then wears the seals and believe it or not the barrel too. fortunately a clutch with an external slave is usually easy to bleed so a regular bleed is recommended. I tend to change clutch fluid on colour rather than time. looks in this case like the debris had started to jam the piston and that was why the piston was hanging up in the barrel, on sudden release it would knock and feel like the clutch was snatching.

When it comes too the concentric clutches, well that's an whole other ball game. If it fails then that's a gearbox out job and when bleeding they are very susceptible to damage. so real caution needs to be applied if pressure bleeding them. Personally I like the back bleeding technique as you have full control and can also empty the reservoir first and fill as you feed from the bleed nipple. some concentric slaves do not have access to a bleed nipple and the ones that do, will require extreme care when loosening and tightening them or setting the stop to the correct position as they are quite fragile and often not supported where they exit the gearbox. If you really don't want to go there just syringe out all the old fluid from the reservoir and refill with new clean fluid of the correct grade. Dot 3 and 4 are compatible with each other, 4 has a higher temp rating 5.1 is a silicone based variant and don't ever mix them or use it in a 3 of 4 system that has previously been used.