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MG Midget and Sprite Technical - Intermittent clutch?

Driving to the granddaughter's soccer game today, and all started out just fine. Then I needed to down shift about 8 miles from home, and the clutch pedal just went to the floor with no resistance. I presume based on what I've read in the archives here that only the pedal return spring brought the pedal back up. Pumped it many times. Sat a while. Pumped it some more, no resistance, no disengaging the clutch.

It's all new, and I mean all new: master, clevis, hard pipe, rubber hose, slave, other clevis, release bearing and clutch. I'm one of those mechanics that compensates for lack of insight by enjoying the thrill of ordering parts and having packages delivered.

Actually had the car towed home on a flat bed. Haven't done that since the car was first acquired in 2001.

Went out this evening and expected to find either the master or the slave had failed. I bought the inexpensive packaged kit from Moss back in April, and I'm sure they'll stand behind it.

Started by asking the lovely assistant to push the pedal while I was holding the rubber hose to see if I could feel it "bulge", and it did. That's when the lovely assistant pointed out that it felt like there was a working clutch.

Yup.

Not certain it catches as high up as it did this morning, but I started it and put it in first gear with no noise at all, seems to be working fine.

Now I'm nervous. I've got a car I don't trust, with no problem to solve.

I've read of others with similar experiences in the archives. I don't think it's the release bearing (maybe it's wishful thinking), but more likely the master or the slave. The fluid in the master looks dark down low, but fine up high.

I'd appreciate any advice as to where I should focus my efforts. I plan to call Moss on Monday as they're often helpful and maybe there's been a pattern with customers of the inexpensive kit. I'd rather not pay the Lockheed prices if I can avoid it.

Thanks for reading.
Mark 1275

Sounds to me like there might have been a bit of rubbish got in the wrong spot in the m/cyl
Interesting that the fluid is dirty if it's all new
I'd be tempted to suck what you can out of the reservoir and refill with clean and give it a good bleed through till it's all clean and i'm fairly confident it will be fine then

willy
William Revit

Thank you, Willie. I'll remove some fluid to get a better look at it.

Not sure what it will take to restore trust that it won't happen again.
Mark 1275

Well, I found the source of the problem, and it wasn't what I expected.

It was a winding path to get there, but a series of problems led me to open the inspection port in the bellhousing and take a bunch of pictures with my phone.

I'm glad the problem is as obvious as it is, and I already started the process of pulling the engine and gearbox last night.

I'm anxious to see how much damage was done. I don't yet know if the lever bolt snapped, or maybe I bent the locking tab washer one too many times and it failed and things just vibrated apart from there.

I'm glad the inspection port is there and gave me the chance to see this.


Mark 1275

Could have been a lot worse. The bolt now looks more like a drill bit, and the nut and tab washer were just neatly nestled in the rubber boot for the lever.

I'm hoping the damage to the pressure plate isn't excessive, and I'd sure appreciate any opinions about that.

Thank you.

Mark 1275

Here's a view of some more of the pressure plate.

Mark 1275

Well done in finding it.

Certainly not something I would have expected, either.
Dave O'Neill 2

It was a strange set of symptoms, Dave, and I'm relieved it turned out to be one, obvious thing.

I'm guessing I must have been lazy when forming the locking tab washer into place. I remember thinking it was hard to get at the part that locked to the bracket. The part that went up against the nut went fine.

I think my gearbox vibrates more than before I tried to improve it, and the tab washer just vibrated off, with the nut, and then the bolt vibrated out.

I've bought a center lock nut, as well as a version of a locking tab washer from McMaster. And I'll use Blue Loctite. Keeping the clutch and pressure plate I've got.

The bolt is toast, so another new one is on the way.

With help from the wife and son we got the engine out in two evenings. We're getting good at this.


Mark 1275

Mark, I am pretty sure you shouldn't use a spring washer directly under the head of the bolt, just the tab washer. Spring washer goes under the locking nut after you have adjusted and locked the bolt. Or use a self locking nut.
That may have added to the problem.
GuyW

It's almost exraordinary that the bolt could work its way out given there's a locknut and tab. I'll double check mine before I install it!
Bill Bretherton

The thread in the cover plate which the bolt screws in to can strip. A self locking nut as Guy suggests will help.
Bob Beaumont

I think Guy is saying that he thinks the spring (split) washer might have been placed after the tab washer so that the depth of the spring washer took away from the effectiveness of the tab washer by 'raising' the bolt head against the tab.

If the tab washer was as poor as the tab washers I got for my brake caliper it'd not be good anyway.
Nigel Atkins

The order for the pin should be bolt, tab washer, spring washer, nut. As Guy says the tab washer goes under the head of the bolt, the bolt is then screwed through the cover plate and the clutch fork. Its then tightened so the fork moves freely. The spring washer and nut is then fitted and tightened but allowing the fork to still move. In effect the nut acts as a locknut. The tab washer is then bent to lock the head of the bolt against the cover plate
Bob Beaumont

Exactly, as Bob says.
The spring washer, if used, is to stop the locknut from slackening off. It's not to hold the bolt which screws into the fork of the casting, and is then locked in position relative to the casting with the tab washer.

The nut and spring washer, or alternatively a nylock type nut, is really a belt and braces addition. Properly assembled, even if the nut did vibrate loose, the bolt shouldn't then be free to drop out. I suspect the thread in the pivot fork may be stripped or at least worn.
GuyW

Much appreciate the responses.

I'll definitely change the order of assembly.

Two more questions: I bought both a nylock nut and a center type lock nut. I was a little worried the bell housing might get hot enough to affect the nylon. I was planning to see how the center lock nut felt going on, and if it seems like a good solution I won't have to worry about the nylon. Any reason not to use a center lock nut? I agree, I'm using belt, braces, and even a little construction adhesive.

Second, I do notice more vibration in the gear shift than I remember. I replaced most of the bearings in the gearbox, and then the entire clutch. Is there something I can easily check to see if my work has created the extra vibration? Should I remove the clutch and realign using my plastic alignment tool because it's a possible cause?

(Here's the tab washer I've ordered. I wonder why neither Moss nor VB offers one.)

Thank you.


Mark 1275

Mark,
that tab lock looks to me, I'd guess there is a price difference between that and the one Moss sell (over with you not available from Moss over here).

That's the end of what I know, I must admit I've often wondered about nyloc in hot areas. I try to only use nylocs once then bin but an engineer friend rekons that there good for perhaps reusing once or twice, but like the other engineering I know he's a tight devil (careful with expenditure on such things).
Nigel Atkins

Mark,
I wonder, might your vibration be in the prop shaft, it having been disturbed and very likely refitted to a different position in relation to the gearbox splines? The shaft itself should be balanced, but if the joint bearings are beginning to wear that might create a vibration since being disturbed.
GuyW

Nigel; I agree with your friend about the nyloc nuts. Based on using the things for decades, but with two caveats.
In general they should not be torqued to the same tension as plain nuts as they usually have shorter (I mean fewer) threads and in aerospace applications it is (I understand) a requirement to discard and replace them after removal. Happily we don't need to worry about that too much!

Mark, nothing in your bell housing should ordinarily get hot enough to worry a nyloc, but given their lower torque tolerance I probably wouldn't use one anyway. I'd prefer the locknut approach (do Americans still call them jamnuts?) or a serrated shakeproof washer.
Loctite is also a good solution. But if you want to be traditional you could drill and lock wire.
Split/spring washers have been mentioned too. The only reason I will ever use them is if there are warranty issues requiring me to use them, because they don't work.

I don't know what you mean by a centre type locknut, but I'm curious if you would be kind enough to describe it. Sounds interesting.

HTH
Greybeard

Mark

No need to realign the clutch. The alignment tool is only to centre the plate so that the first motion shaft will go in on first assembly. Once you’ve pressed the clutch pedal, you’ve unclamped it, anyway.
Dave O'Neill 2

Nylocs should be fine in this service as their upper limit is about 120C. All metal locking nuts are readily available if you're worried.

What is a center type lock nut? I've never heard the term before.
David Billington

The prop shaft does get attached to the differential in the same orientation each time I reassemble, but not at the gearbox. Maybe I'll get luckier this time.

Didn't think about the clutch disc recentering on its own. That's the beauty of this forum for people like me.

A center lock nut is a regular nut, but someone hits it really hard with a punch so the threads are slightly distorted. That makes it harder to get on, so hopefully harder to vibrate off.

This picture isn't what I expected to find at the hardware store, but it's what I bought. It's all steel.


Mark 1275

This is what I expected to find at the hardware store.

Mark 1275

Ah! Thanks Mark - I get what you mean now.
Greybeard

Mark,

The first looks like it might be a Philidas MKV nut, often referred to as a Philidas mk5.
David Billington

This thread was discussed between 08/09/2019 and 03/10/2019

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