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MG Midget and Sprite Technical - Bleeding Clutch

Seems a popular thread at the moment......
OK, having had clutch go bang on me whilst on way to holiday (grrr), got car back home, engine & gearbox out, new clutch, plate, needle roller thrust bearing and other parts.... sorry getting off thread.
I got a new slave cylinder and hose. Went to bleed clutch with Eezibleed. Closed bleed nipple when no bubbles, but no pressure on pedal still. Put front offside wheel onto car ramp to assist angle of bleed nipple. Still same sympton. Firstly bubbles, then clear, but no pressure on pedal. Swapped the new slave cylinder for the original one (the clutch pedal still had pressure after the breakdown with the original slave cylinder). Tried again, same sympton. Tried the old way - open nipple, press pedal and hold, close nipple, release pedal etc.. No different. Fitted a new master cylinder. No different.
(I even tried removing the 2 bolts on the slave cylinder and uncoupling the split pin, so that the bleed nipple could be totally upright, feeling confident I could get back under car before the pressure got there. WRONG.
Don't try that one.)
Am totally flummoxed - any ideas???
(Have decided to start calling the car Christine. Those of you who saw the film will understand why)
Geoff Mears

did you push the piston all the way into the cylinder of the slave to remove any trapped air there? Sometimes works
Bob Beaumont

No, but I will point out that you can remove the master cylinder, pipework and slave cylinder, tinker with the thing on the bench until it works and then refit as a unit which is what I ended up doing last time mine played up. It's a whole lot less annoying that way.
AdrianR

Check under the car to see if the lever arm is moving fully as someone else presses the pedal. If it isn't moving fully then it's an hydraulic propblem. If it is but still no pedal, then you have a problem inside either with the thrust bearing or the clutch itself.
GuyW

Bob, No I didn't. Do you mean disconnect the piston and manually push it in whilst in situ?
Adrian, May have to go that route if all else fails
Guy, Will enlist the help of an attractive assistant to check. Thrust bearing and clutch are brand new. I'm thinking that it must be a trapped air problem. Up to when the clutch/bearing and gearbox front cover (one of the 2 fixings that the release arm is bolted to snapped clean off) gave up the ghost I never had any problem with pressure in the hydraulics.
Geoff Mears

Geoff,
Had same problem, fixed by bleeding the master cylinder using positive pressure through the mc cap then cracking the mc outlet pipe nut whilst glam assistant puts pressure on the pedal....satisfying release of air resulting in a firm pedal.
Good luck,
John
J Sloan

Yes Geoff. It is most probably a hydraulic problem but it is still worth checking the lever arm movement if only to eliminate the possibility of an internal clutch issue. Else you could spend a lot of time chasing round the hydraulics and still not resolve the problem!
GuyW

Yes, Geoff - as Bob suggested, I would get a lassoo around the slave, rod and fork end, and tie it off with the piston right in. Then bleed.
Remember to untie it before you test the pedal, and if you doubt your memory (as I do mine), use twisted garden wire or something else that will let go when you forget.
Nick and Cherry Scoop

Thanks all for suggestions.
John, not sure I quite understand. How do I put positive pressure on mc cap?
(If you mean use Eezibleed I'll need to get another as mine only fits small cap mc and the new one is large. Alternatively I can put the old cylinder back on - grrr).

Also,mc outlet pipe nut - I assume you mean the one that goes into the top of the mc into which the hydraulic pipe fits.
Should glam assistant press and hold, or pump?
Should the bleed nipple on slave be closed?
I assume air comes out by outlet pipe nut?
Geoff Mears

Geoff,
I had assistance from a 'proper' mechanic who had a pressure vessel like a garden sprayer...but bigger.He had a range of caps to fit.MC was filled to brim and pressure applied with SC nipple closed.He applied the pressure and cracked open the outlet pipe connector to the MC whilst I (err... the glam assistant in this case) I tried the pedal a couple of times....did not pump it as there was a hard pedal almost immediately.You are correct that the air came out of the outet pipe where it had been opened a litte...put wad of paper underneath and lock it back up if/when air is released.I had been bleeding the SC endlessly via a remote so it was OK but you may then have to go back and bleed the SC.
Good luck,
John
J Sloan

Thanks John. Understood. I really must get a remote made up.
In the meantime I have just tried Nick's suggestion. There is only about 5-6mm of play in the fork movement. Pushing back by hand I hear what I presume to be thrust bearing touching clutch, and then pushing forward by hand it will only go the 5-6mm, which I assume to be ok as the release arm can only go so far in the "wrong" direction. Finally the bleed produced no further progress.
Guy, got glam assistant to press pedal. Rod moved towards back of car as I would have expected and then back again when foot off pedal. Probably about 2cm movement overall. So unless you tell me differently it looks like hydraulics.

Looks like I'll be going to Wroxall on Sunday in the Eurobox.
Geoff Mears

Surely wrong conclusion, Geoff. Looks like in-bellhousing problem.
I remember how I laughed after I put the clutch fork in the wrong way round, for example.
Nick and Cherry Scoop

Correct Geoff. Hydraulics. Which may not seem like good news but it is as the alternative would be summat wrong inside and require engine removal!

It's just air in there, reluctant to be wafted away.
GuyW

Tried Bob's idea, which to be fair did produce a few bubbles. I continued until no bubbles and found there was an element of pressure on the pedal, although not enough to engage gears.Inspired by this, I codged up a pressure vessel using my Eezibleed and connected to master cylinder and cracked open the nut. No sound of escaping air so pinched it up again. Pedal has now gone back to totally useless, so all I have achieved is pumping more air into the system and am now back to square one. I didn't have anyone to press the pedal, so I'm sure it is all my fault. Have put car back in garage. Will start again when the mood takes.
Nick, the clips that hold the release bearing in place have the snap on part facing outwards, as is the bearing face. I'd send a photo but have forgotten how to reduce the size.
Geoff Mears

Nick, Remembered how to reduce size.


Geoff Mears

Sorry to be the bearer of bad news Geoff, you have the arm the wrong way round. The clips need to ne at the back and the arm needs to face the other way. The arm is slightly curved so that explains why you don't have the correct spacing and free play. Pic follows.
David Smith

Bob / Nick : When you disconnected the rod on slave cylinder and pushed it right up the cylinder, did you then tie it in that position, and then bleed it, and then untie and reconnect to the release arm. Then check pedal travel.
Geoff Mears

as you look into the bellhousing...


David Smith

rear view if you were a fly on the gearbox front cover plate...



David Smith

and side view showing the slight curvature of the arm, plus the offset of the pivot forks. When installed facing the wrong way the arm hits the edge of the hole in the casing before the bearing touches the thrust plate.


David Smith

David, many thanks for solving the problem. At least I know what I've got to do. A job for next week methinks.
Nick, You get the prize for being right. I'm sure you can hear me laughing, just as you did.
Thanks to all you guys for your imput. Greatly appreciated.
Geoff Mears

Blimey, David got three photos up whilst I was looking for one and amending it.

Even though David has covered it all I'll put it up as a comparison to Geoff's for future reference perhaps.



Nigel Atkins

Nigel where do those funny bent wire clips come from? Never seen them myself, they look horrid compared with the spring steel MG / Borg & Beck ones.
David Smith

They're from earlier Spridgets and MGAs.

Not my choice David either, 'specialist experts' used them as part of their garage clear out of odd left over parts to cobble together a gearbox conversion kit.

They seem to fit the bearing in that photo and as a MGA competition bearing was used as a later replacement I think they went back in but they didn't fit one of the arms that well as IIRC one clip might have been missing at one of the clutch episodes.

Nigel Atkins

Same version fitted to the Morris Minor ribcase box I have.
GuyW

Hi all.
I think I'm back to square one, but with a little more information. Did all the things everyone on here has said to do, and to be fair the pedal did feel as though it was "in the zone". But I tried to get into 1st and just got crunchy "you're not coming in here" noise. Forced it into second but when I released clutch all I got were whirry and clunky noises. Same in fourth. Couldn't get third.
I'm thinking that I have another problem as well.
When the breakdown happened I was just pulling out into slow moving traffic and (I think) as I released the clutch there was a bang from the bellhousing area, and I didn't have any drive. I think I could put it into a gear but no drive.
When I took the engine out the thrust bearing was totally worn away, although I did not have any warning screeches or anything - until it happened. I'm beginning to think now that I had two problems, but what!!!
I have a horrible feeling that you are going to tell me it is an engine out jobbie again.
Geoff Mears

Just try something Geoff. Engine off, put it into gear (2nd or third) and try pushing it. Handbrake off of course. You should find it hard to push as it tries to turn the engine.

If it is relatively easy and the engine doesn't turn then the clutch driven plate may have disintegrated, or maybe you have broken a half shaft. Listen for and try to locate the direction of any graunchy noises.

When you had it apart again, did you inspect the clutch plate? Sure its the correct way round?
GuyW

Hi Guy
Have tried pushing car in gear as suggested. There is resistance like you would expect, but it is like the car is trying to lift itself up. Also there are graunchy noises coming from the back end........
Geoff Mears

Geoff, I suggested that test as if it pushed relatively freely, one might suspect that the centre had pulled out of the clutch driven plate, which would result in no drive as you described. But that sounds Ok.

Noises from the back plus loss of drive does rather suggest a broken halfshaft. Jack one wheel up at a time at the rear, and WITH THE CAR IN GEAR and the other rear wheel either firmly on the ground or chocked to prevent it turning. If the raised wheel turns then that would indicate a broken halfshaft on that side.

It remains though, if it won't go into gear smoothly then it seems likely that your clutch isn't disengaging fully. This is most likely a hydraulic problem but you do appear to have given that aspect a lot of attention. Clutch driven disc in the wrong way round would give similar effect though.

GuyW

Geoff, when you say the thrust bearing was totally worn away, was the worn away bit still in its housing? We had the carbon break up completely, and its housing severely damaged, but it didn't go bang. More of a screech.
Can't wait for that half shaft test. No, don't stop for lunch. Get out there.
Nick and Cherry Scoop

Sorry Nick, but I had my lunch first. To answer your question, the thrust bearing was still intact - just worn completely level to the metal surround. No damage to housing). I agree with your sound effects as the norm for a clutch going west. I'm thinking now that perhaps I assumed that the bang came from the bell housing, because following Guy's instruction I jacked up each wheel in turn leaving the other wheel firmly on the ground, put into second gear - BOTH wheels turned freely. There was a bit of resistance, but when I turned the wheel the other way I got graunchy noise and a sense of minor resistance. I stopped momentarily and then continued and it turned freely. From the noise clearly all is not well in that area. But both ? !!!
I expect I'll have to take the engine/gearbox out for a third time, but I'll leave that until I have resolved the problem at the back end. Maybe the new clutch and new driven plate have issues. Certainly some new parts are not all they are cracked up to be. I'll be returning the new (plastic) master cylinder which leaked like a sieve to Leacy, hopefully for a refund.I put my old one back one, which didn't leak. The 2 new clips for the clutch bearing were too big, and could easily spin round! I didn't fit them - I used the existing ones again which were still ok.
Geoff Mears

Geoff, both turning freely doesn't mean both halfshafts are damaged. It will just be one side, but if side A is broken, then when you jack up side B to test it, chocking side A wheel doesn't stop the diff from turning as the shaft is broken.

Cannot remember if there is a way to identify which side had gone though. Maybe the noises will tell you? Or someone else confirm?
GuyW

In closing, it was nearside half shaft which was the culprit, broken in the splines as you would expect.
Again, many thanks to you all.
Geoff Mears

Thanks for posting the answer.
Nigel Atkins

This thread was discussed between 23/08/2018 and 06/09/2018

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