MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Clutch rattle

When the car is warmed up on tickover an annoying rattle is heard I think coming from the clutch as it disappears once the clutch peddle is depressed. I was informed it could also be crank movement that is stopped when the clutch is depressed. Any ideas on how this could be identified. I am hoping it’s from the clutch and if it is would it be easier to change the clutch by just removing the gearbox rather than taking the engine out. Thanks. Trev
Trevor Harvey

I'm not going to try and diagnose your rattle, but I wanted you to know that you can't remove the MGB gearbox from underneath. If it's a clutch problem you have the option of removing just the engine (which I prefer) or taking both engine and gearbox as a unit.
Mike Howlett

Trevor what release bearing are you using?
Colin Parkinson

How far do you have to press the pedal for the noise to stop? How soon does it restart as the pedal is released?

If hardly any distance it could be the pedal pivot/linkage, if when you start to feel the 'weight' of the clutch it could be the release arm/bearing. But if the latter them you should be able to feel it by reaching under at idle.

The slave cylinder is supposed to have a spring that pushes the piston out and hence pushes the release bearing into contact with the cover plate. This makes the clutch biting point consistent as well as compensates for wear as the graphite release bearing wears down.

The crank and hence the clutch can move back and fore as thrust washers wear, but if significant that should be visible by looking closely at the pulley while the pedal is operated and released at idle.

As it happens it _is_ possible to take a non-OD gearbox out of a 4-synch car, but having read what's involved I don't understand why anyone would bother. Particularly for a clutch when only the engine needs to be removed, and having done it and been involved with doing it both ways for gearbox work more than once on my own car I opted to take engine out first and then slide the gearbox out from under the car rather than take them out together.
paulh4

Colin, I rebuilt the engine about 5/6 years ago and fitted a new clutch with a graphite thrust bearing, the car has only done about 4000 miles since.

Paul, Good information as usual. If I can eliminate the possibility it could be crank movement by looking at the front pulley as you suggest that would be great. I have thought if the rattle is coming from the clutch it would probably be the springs in the clutch plate but if it could be one of the other things you suggest that would be useful.Checking the release arm bearing, do you mean through the hole after the rubber gaiter has been removed.
Trevor Harvey

If it is as you say only after it warms up--maybe-- your gearbox oil level is low----bit hard to diagnose rattles without hearing it but the gearbox noise is a deeper clonky/clatter/rattle type noise that disappears with the pedal depressed from about 1/3 way down onwards when the clutch disengages

A rattly clutch fork tends to stop rattling higher up, more like as soon as you start pressing the pedal, even just resting your foot on the pedal
William Revit

Feeling the release arm where it exits the gaiter, I'd expect to feel a rattle from the release bearing there. Possibly a clutch spring, and you may also feel that in the release arm, either almost certainly means engine out in the longer term at least.

But you can just see the release bearing by pulling the gaiter back, although I've never done that with the engine running! You can just about gauge graphite bearing wear that way, the attached from Mike Dixon. 'A' are the diaphragm springs, 'B' is the edge of the release ring that the release bearing presses against, 'C' is the graphite ring on a new bearing, and 'D' the bearing casting.


paulh4

Thanks William, The oil level in the gearbox was low, Idiscovered the overdrive was leaking from the filter plate, had to put over a litre of oil in it to top up. I have a filter kit to remedy the leak and was intending to do it at the end of the summer but maybe I’ll do it sooner but for now just make sure the oil level is topped up. Thanks for your help. Trev
Trevor Harvey

Nice one Trevor----and easy on the wallet--good result
William Revit

This thread was discussed between 21/06/2023 and 23/06/2023

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now