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MG MGA - Holmes needs help sleuthing

I've never had this happen before and I can't figure out the cause. I hopefully can't replicate it either.
I was backing out of my garage and up the driveway which is quite narrow and had to stop, put it into 1st and pull up a bit to readjust. When I put it into reverse and started backing up again I put in the clutch but it did not disengage. The clutch was fully depressed. I had to pop the tranny out of reverse to stop. Now, being 100% male, I thought to myself, "That was weird" and I re-engaged into reverse, backed out the drive and went on with my beautiful Santa Barbara drive-about. Perhaps, I should have just put the car back into the garage to sort things out and be safe. But, no, I figured I'd just drive a while to see if it happened again. It did not. MGA 1500 all stock. I look forward to your wise counsel.
David Holmes

David,
Sounds like the clutch plate may have stuck tempoarily to the flywheel disc due to oil, rust, dirt, or some other issue. If the car had been sitting for a while previous to this it might cure itself. I wouldn't expect that you would harm anything by driving it, but you would have to be mindful that it could stick again. I wouldn't follow anyone too closely for a while! Parallel parking might not great either:>) Good luck.

Ralph
Ralph

David,
About the only thing that would stop the clutch from disengaging, barring a mechanical failure, would be loss of hydraulic pressure. I would start by checking the motion of the slave cylinder. Did the clutch force seem normal? Still, an "intermittent" loss of hydraulic pressure would be quite unusual. You sure it was the clutch you pressed?...:)
Quite curious.
GTF
G T Foster

David, try putting the car into gear and holding the clutch down. Now just wait and see if, after a while, the car begins to creep (as if you lifted the clutch pedal slightly). If it does, raise and depress the clutch to operate it normally again.

If you have these symptoms it's most likely time for a new master cylinder seal kit! (It could also be the slave cylinder, but then you will find fluid leaking from there.)

The master cylinder may not be leaking as the primary cup seal is leaking, but the secondary seal is still ok.

Neil McGurk

I had this happen to me with the brakes on a Fiat 600 back in the early 1960's. Stepped on the brake pedal at a stop sign and it went to the floor without applying any brakes. Quite a thrilling moment. Lucky for me there was no cross traffic. The next time I stepped on the brake pedal all was back to normal. It never happened again but I drove like a little old lady for a long time after that.
Ed Bell

It sound like there was enough friction even with the clutch "disengaged", to still feed drive to the gearbox. If the clutch friction plate had been stuck to the flywheel the pedal I would have thought that the pedal would have felt as if it was jammed also with very little movement apparent.

Also, if you had mistakenly pushed the brake pedal as hard and as far as the clutch pedal would normally go, then your car would probably not have been able to move at all.

My guess is that there was some corrosion or crud on the plate and flywheel which caused the problem and which has now rubbed off with use.

Next time you start the car in the garage I would start it in reverse with the clutch pedal pushed down and if the car lurches backwards on the starter it will at least pre warn you and prevent a repeat of your runaway reversing MGA experience.

If it happens often then it looks like a new clutch and/or a refinished flywheel may be needed.

On the subject of clutch-brake pedals, I had a frightening experience years ago when I was looking at a Trident Venturer in a backstreet garage forecourt.

The car was a Kit car of the 70s based on a Ford three litre straight six engine, a sort of wedge shaped fibre glass sport saloon 2+2. Lots of power for its weight and a bit different from my Hillman Imp of the time.

The salesman came out without prompting and handed me the keys for a test drive and sent me off in the car on my own. So with a nervous grin I floored the throttle and few out of the forecourt. I zoomed off down a long but quiet side road that joined a busy main road about a mile away.
So I kept my foot down and got up to about 60mph before I hit the brakes to slow for the main road.

I was more than a bit shocked to find that the brake pedal just went straight to the floor with no effect on the speed and I hit the main road at over 60mph!

I recall just having time to say "Oh s**t!" or its equivalent before flicking the steering wheel left as hard as I could to get the car to slide sidewards onto the main road "Dukes of Hazard" style.

Amazingly the car slid sidewards on the main road and slotted perfectly into a two-car space in the traffic accompanied with lots of blue tyre smoke and much blowing of horns!

So a very sweaty and adrenalin flushed me returned to the car dealer less than 5 minutes after leaving it and I recall the puzzled look on the salesmans face when I said that I dont think its the right car for me!

I realised after my near miss that I was used to driving a tiny Hillman Imp which has pedals "very" offset towards the centre of the car to avoid the wheel arch. The pedals in the Trident were in the normal outside location and when I went to brake hard my foot pressed onto the clutch pedal by mistake!

Not an experience I wish to repeat!

Colyn
Colyn Firth

Check the rubber hose to the slave. It can fail internally without any sign on the outside. Sometimes when the hose is old, the fluid will just expand the hose, ie, no movement of the slave piston occurs.
Peter.
P. Tilbury

Thanks gents for your fine sleuthing.
David Holmes

David, don't forget to let us know what you find!
Neil McGurk

This thread was discussed between 16/11/2010 and 19/11/2010

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