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MG Midget and Sprite Technical - Rear hub leak

Hi I have slight leak from between the half shaft flange and hub . I replaced the paper gasket and O ring a couple of weeks ago but still seems to be there . Should oil actually get to that point or should it not get passed the hub seal ? . I did try on the wheel and torqued it up to ensure it was tight fit then rechecked the cross head screw.
Mike Fairclough

When parked level the oil does just about get to the hub, indeed it has to to lubricate the bearing. The lip seal is to stop leaks from the back of the hub. There are of course 3 crosshead screws, one for the hub flange and two for the brake drum. If even one is not quite home the flange might not seal. If you are sure they are all OK, then the gasket and O-ring are the only other items that can be at fault.
Les Rose

One possibility that's not common but does happen is the flange is cracked allowing oil to leak DAMHIK. This is typically a crack around the bump in the flange and more common in race cars but I had a halfshaft fail completely in my road car at that point.
David Billington

When I had my hubs apart I discovered that they were no longer flat. Years of tightening the wheel nuts had distorted the flanges. I ended up removing the studs and carefully filing the flanges flat (checking with a straight edge). I didn't measure the distortion but it could easily have been enough that the gasket was compressed where the studs are but not compressed much at all between the studs.

Once you are satisfied that the hubs are flat, measure everything very carefully and make sure you have gaskets the right thickness or make some from the right gasket paper. It is not difficult to do if you have a sharp scalpel or modelling knife.

Jonathan Severn

Also worth checking that the breather on the diff case is not blocked.
It's a plastic widget on the side of the diff case a little higher up than the filler plug
In theory you can unscrew it, in practice it will resist you doing this but will let you pull the cap off and poke something in to remove any build up of muck.
If blocked then pressure builds up which can help to force the oil past the seal into the brake.
Richard Saxton

Thanks for all your comments. I hadn’t run the car with new gasket it had happened while standing . I’ll leave the car level for a few days and see if it weeps after retightening the cross head screws . If so I’ll have the shaft out and check flatness etc of the flange . Whilst under there I will have a check of the breather thanks
Mike Fairclough

I find the gaskets supplied by the likes of MOSS etc are too thin. Also the bearing is meant to be pre-loaded which means in some circumstances the thickness of the paper should be chosen to provide this preload. Malcolm LeChevalier is the expert.
Rob
MG Moneypit

Worth some very careful investigation to distinguish whether the leak is indeed the hub flange, or the lip seal at the back of the bearing. You could spend a lot of time trying to cure the wrong leak!

When I replaced my rear wheel bearings I fitted ones with a built in seal at the back face, plus used the normal oil seal for double protection. I did wonder if the lip of the seal would overheat if it ran dry but at last inspection that didn't seem to be happening.
GuyW

Are they pre loaded? I hadn't thought so. The inner race is an interference fit on the axle shaft, and the outer, which should be an interference fit in the hub, is also clamped in by the halfshaft flange, if the correct thickness paper is used for the gasket.

I wondered about the oil seal running dry if the rear face of the bearing is sealed. But several people have said that doesn't happen.

The other option is a speedy sleeve to restore the shaft surface.
anamnesis

Speedy sleeves are pretty expensive items these days, as I think you found?
GuyW

Yep it was a tad, but much cheaper and easier than a new or weld/grind on the crankshaft.

Did I read some people have used fully sealed rear bearings?

As long as the grease isn't contaminated/diluted by axle oil, they should last yonks, and I guess the oil seal could be omitted, or the inside face of the seal could be loaded with grease too.

Hopefully, I'll never need to find out, as I expect mine to last me out now. Lol.
anamnesis

I always start sweating when someone calls me an expert! ;-)

Anam is correct, gasket thickness is key for ensuring the correct clamping of the gasket between the hub and half shaft. Too thin is better than too thick IMO.

Lots of people have reported using double sealed bearings. For me, they are a bit of a bodge. I don't think there is much wrong with the original system if built well with good componentry and a 2RS bearing is designed to keep grease in/dirt out, not nessecarily as an oil barrier. But if they work and people are happy with them, so be it.

The one thing I would like would be a double race bearing for a bit more control... but that's a whole different kettle of fish!

Best of luck.

Malc
Malcolm

Malc, mine aren't double seal bearings. Or rather they are, but I removed the inner seal so the bearing still gets lubricated with the axle oil. It of course makes no difference to the half shaft flange seal and bearing clamping arrangement.
GuyW

mine was the rear seal so fit speedi sleeve found them for less than £20 each so not that bad this could be useful
https://www.mgexp.com/article/mg-midget-and-sprite-rear-axle-knowledge.220
mark heyworth

Typo in what I said above...

Anam is correct, gasket thickness is key for ensuring the correct clamping of the gasket between the hub and half shaft. Too thin is better than too thick IMO.

should read...

Anam is correct, gasket thickness is key for ensuring the correct clamping of the BEARING between the hub and half shaft. Too thin is better than too thick IMO.
Malcolm

This thread was discussed between 30/04/2022 and 04/05/2022

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