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MG Midget and Sprite Technical - Heavy Oil in the Drum AGAIN

On top of my bleeding problems, here's a depressing but familiar sight - a lovely black mixture of brake shoe and EP90 all over.

I recall from the last time that the halfshaft endplate clamps the outer casing of the bearing, and the gasket and O-ring have to fill the gap from endplate to hub face. I think it was about 11 thou. Current gasket offerings are miserably thin, and I don't want to use the safe but sad sealant solution.

Does anybody know of a gasket of adequate thickness?
Nick and Cherry Scoop

Malcolm to the rescue with one of his gasket kits? If he has any left that is.
GuyW

I thought the gasket was supposed to be thin and that the gaskets supplied today are too thick?

The ones I have in the kits from Rimmers look too thick to me, I’ll measure them if you like and let you know.

Nothing wrong with gasket sealant, I use it on every gasket apart from the cyl head.
John Payne

Nick
I had a supply of NOS BMC gaskets and the latest offering do not seem that different. The procedure I use for the hub is:
1. clean all mating services ie the half shaft and the hub carefully, I rub them over with coarse wire wool to make sure and then wash with clutch cleaner.
2. Use a new gasket and O ring.
3. I use blue hylomar on the joint faces so carefully coat the hub and the halfshaft thinly. Fit the gasket.
4 Install the halfshaft. Clamp up with the set screw.
5. Put on the drum (brakes slacked off) and tighten the other two set screws.
6. Retighten the halfshaft set screw through the hole in the drum. I find the set screw can often go up a further 1/4 turn.
7. Check the drum set screws again are tight.
8. Adjust the brakes.

Using this procedure I have not experienced problems. I even have a slightly loose bearing fit one rear hub but it all seems to pull up ok. I also makes sure the set screws are in good condition and the screwdriver fits snugly.
Bob Beaumont

I *never* use any sort of sealant or mastic or goo on gaskets. If the parts are all clean and correct it is not needed. Ergo, if it's needed then something is wrong.
With the rear hub seals I always go as far as refitting the road wheel and tightening all 4 wheel nuts up evenly, then leaving the car on the jackstand for an hour or two for everything to settle. This is a good way (possibly the only way?) to clamp the seal and gasket evenly.
David Smith

Yes, I remember now. It was Malcolm who did them. Thanks, Guy.
Thanks all. I will try your beauty treatment, Bob, and hope that, in conjunction with a correct gasket, I manage to get a seal. The gasket that's come off is uncompressed, I would say, and it's 0.004" thick. It was new from one of the usual suppliers.
I'd be interested to know the thickness of your Rimmer gaskets, John. I make the step between hub face and bearing case 0.010"

David, I followed the same process as you, and with no oil in the axle at the time, though the wheels have been on and off many times since, with my bleeding problems. I must confess that when I removed the drum all three screws were at least a quarter turn slack. I should have checked them every time the wheel came off.

I would prefer not to use sealant.
Nick and Cherry Scoop

I make it about 0.030”

If they are too thick then the hub doesn’t clamp the bearing leading to wear in the hub. I think 0.010” is the preferred thickness.


John Payne

Its an odd combination. I do understand the relationship betwen paper gasket thickness and the necessary clamping action of hub flange onto the bearing. But one might reasonably expect that the design with the large squishy O ring would on its own retain the axle oil. So why both paper and O ring?

Can anyone give a logical explanation for the design?
GuyW

Originally there was no O ring just the gasket. it changed with Morris Minors around 1956 or so I gather presumably because there were oil leak problems.
Bob Beaumont

Ah, OK. But why then continue with the paper gasket? Belt and braces?
GuyW

Couldn't agree more, Guy. I've always thought the O-ring should do the job.
Nick and Cherry Scoop

I assume so. The O rings does put pressure on the gasket to maintain the seal. The gasket I assume remains to ensure the end float on the hub is maintained as the bearing does sit slighty proud. Perhaps open bearings were only available then. A sealed bearing would probably do the job without all the malarky
Bob Beaumont

Thanks Guy! Hello! :-)

Let me catch up. Hang on....
Malcolm Le Chevalier

I’m sure I measured my NOS gaskets at abou .011”, but would need to check. .030” sounds a bit on the thick side.
Dave O'Neill 2

I am not "officially" doing rear bearing kits right now, but if you are in a bind for a gasket I still have some materials and can sort something out.

Two things from my messing with rear hubs and bearings:

1. From hubs I have had chance to measure the bearing sits in the region of 8 thou proud, 11 seems a little high, maybe this is reducing the compression on your o-ring?

2. A paper gasket will compress to approx' half it's thickness under load. So, for the above example, the 30 thou will compress to approx' 15 thou, thus leaving 7 thou float in the hub/half shaft. Not good, and I believe (although I have no empirical evidence) this is one of the contributing factors to failing half shafts. 30 thou is way too thick. What brand of kit was it John?

Whenever I have done the job I have done what others have already said. Tighten up some nuts onto the studs, then do up the retaining screws. The wheel nuts provide the real clamping force, the screws just stop things falling apart when the wheel is off. I still get a bit of a leak if I have the drum off and the screw is at 12 o'clock, not 6 o'clock.

Cheers,
Malc.
Malcolm Le Chevalier

good info in here. Worth checking, though, that it is indeed the gasket/O ring that's leaking and not the hub seal itself.

as a veteran of oil on the rear brakes (usually due to track day stresses) I've never actually had a gasket/O ring fail, even though I've spun bearings in the hub. It's always been (for me) the rubber seal on the axle casing.

If it is that, then there are things called SpeediSleeves, which are very thin stainless rings that press (tap/force/belt) on to the axle and give a clean smooth surface for the seal to run on.
Rob Armstrong

Good point, Rob but I'm struggling to envisage a cross-section through the hub assembly. If the oil seal is leaking, what's the path of the oil to reach the inside of the drum?

Malc - my last gaskets overlapped the O-ring, so no chance of reducing the clamping. Should they overlap? I would be very glad if you could let me have the correct thickness gasket material, or point me towards it.
Nick and Cherry Scoop

. . . . and another thing:- I was disappointed to find that adjusting the shoes to kiss the drum took up most of the ratchet on the snail. Not much left for later.
I measured the drum, and made it 7.022" after 300 miles over the Wroxall weekend from new.
Nick and Cherry Scoop

Malcolm's ya man for gaskets.

Oil path is along the axle next to the half shaft, where it goes through the gap between the inner race and the shaft, filling up the dish in the end of the shaft sad doing the job of lubricating the bearing. From there, it runs backwards through the ball race itself and gets 'held in' by the seal.

Other thing that's not been mentioned is the breather on the axle - this has got to be clear. With mine, When I let the diff oil out I can hear a hiss as the air going into the axle goes through the breather.



The (best?) failure I had was stressing the single row bearings so much that the bearing wore, the hub flexed on the end of the halfshaft, knackering the bearing more, and lifting the seal off the axle. there was so much flex in the hub the drum had scored a line in the backplate. Oops.

Mine appears (touch wood) to be OK now - double bearing hub with an upgraded double lip seal, speedisleeves, sealed bearings in the hubs, plus a set of decent gaskets from Malcolm.

Oh, and so it's here - Speedi sleeve for a Sprite MG midget rear axle (there you go google for future searchers) is SKF CR99174 Hardened Stainless Speedi Sleeve for Shafts 1.747-1.753 inch. I got mine from Simply Bearings.com
Rob Armstrong

Third in a row - not good.
But I had to confess that I haven't told the truth: I measured the gasket with the caliper set to mm, and as you know I have no engineering instincts. So it isn't 0.004". It's 0.016", and it laps over the O-ring.
The O-ring snugly in its groove is 0.030" proud of the hub face.
The bearing case is 0.011" proud of the hub face.
So, for the endplate to clamp the bearing, it must try to compress 16 + 30 - 11 = 35 thou.
The picture below shows the result.

The leak pattern showed that the oil has almost certainly passed across the outer face of the gasket. I think the hub seal is OK. Sorry about my earlier inane question, Rob: I was full of breakfast and hadn't taken a look.

Edit:- thank you Rob. Good of you to answer so comprehensively.



Nick and Cherry Scoop

No worries :) sounds like it's the gasket - get a thinner one and see how it goes.

Another trick I employed is to put another screw in to the half shaft, so instead of 1 there are 2. I was kindly supplied with some countersunk Allen ones. I seem to remember I needed to countersink another hole in the halfshaft.

I like the gasket looking forlornly out of the window.
Rob Armstrong

Yes, that would be sensible, and while it's all apart, I might try it.
I've been through all my gaskets, and found one of 0.025" and two of 0.013". Same part number, of course, and same supplier. Also two O-rings which are thinner than the one that came out. But perhaps oil swells rubber?
Nick and Cherry Scoop

Another one of my tricks - the decent countersunk Allen screws ;-)

Nick, drop me a mail on chevalierclassics at gmail dot com and we can sort something out. It will probably be the end of the week before bits are with you though, so not good if you are in a rush.

Cheers,
Malc.
Malcolm Le Chevalier

I do need to get on the road, Malc. What do you think of using the 0.013 new gasket, which I've found? I may as well, and if it goes quickly I'll be in touch.
I will be in contact about rear dampers, though.
Nick and Cherry Scoop

There are some thin O rings around. I don't like them as they dont fill the groove in the hub and may leak. I got my last lot from AH spares and they were the correct diameter.
Bob Beaumont

Is it just one side you need? If so, email me on the aforementioned address, you might be in luck ;-)
Malcolm Le Chevalier

Done.
Nick and Cherry Scoop

Bob - can you tell me what the correct diameter should be? I have two quite different options but, as you see above, the fat one wore through the gasket, so proud was it.
I think that particular one would be a good candidate for Guy's idea of O-ring on its own.
Nick and Cherry Scoop

Nick

Will have to check when I get back home tonight. But the O ring should sit snugly in the groove so that when the gasket goes on top it all squeezes together and is oil tight. The thin O rings I have seen do not properly fill the groove in the hub and therefore increase the risk of an oil leak.

As I mentioned the ones from AH Spares are correct.
Bob Beaumont

Thanks Bob. I see from my invoices that the fat O-ring that destroyed my gasket did come from AH Spares. But then, the gasket was 0.026 - much thicker than it should have been.

It was a bit urgent, so it's all back together now, and I have used the thinner O-ring, so we will see what happens. Otherwise I followed your cleaning regime almost to the letter.

Can anyone explain why, after our 280 mile Wroxall adventure, all 8 wheel nuts on the nearside were 45lbs spot-on, and all 8 on the offside were a few pounds down?
Nick and Cherry Scoop

Corriolis force, travelling west to east before noon and then back again in the evening.
GuyW

O-ring is a 3" x 1/8". Or 76 x 3mm metric equivalent.

Malc.
Malcolm Le Chevalier

Old discarded oil rings are quite good for fitting round the tacho or speedometer when fitting to a dashboard.
GuyW

You've hit it, Guy. Your explanation is perfectly satisfying.
I also admire your recycling force.

Wouldn't you just know it:- tomorrow morning's event has been cancelled. I could have waited.
But then again, Laura has just said, "where shall we go then?" so it was worth it.
Nick and Cherry Scoop

Just measured the O-ring that came out, and it's 0.125".
The new one I used this morning is 0.113", with a 0.013" gasket. So that might not work.

But it might.
Nick and Cherry Scoop

This thread was discussed between 01/09/2018 and 03/09/2018

MG Midget and Sprite Technical index

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