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MG Midget and Sprite Technical - Rear Hub Oil Leak

I've got a rear brake assembly covered in black oil with added grease.

Is the probable leak between hub face and halfshaft endplate the only possible route? I can't think of another, but then my engineering memory is less than tenacious.
Nick and Cherry Scoop

Not sure of any other leak paths, but perhaps pull back the rubber covers on the brake cylinders to check they are not leaking as well.
Jonathan Severn

Either there, or the oil seal behind the wheel bearing?
John Hutton

Thanks. It isn't the cylinder, though that's a miracle these days. John, isn't the inboard oil seal to stop oil climbing out over the shoulder of the tube?

Presumably that black mixture of oil and brake dust lubricates the bearing: what a horrible thought.
Nick and Cherry Scoop

There is a a lipseal at the back of the hub to stop oil from the axle which also lubes the hub bearing, escaping everywhere!Easy to replace as long as the surface it runs on isn't damaged.
Graeme Williams

I think the early cars like yours, Nick, used a felt seal at the back of the bearing rather than a lip. If it hasn't dried out I think they work better as they don't wear grooves in the contact surface.

I would suspect the hub flange rather than the bearing back seal.
GuyW

I.m pretty sure you're right, Guy. A back seal failure would presumably let oil out onto the wheelarch and the road (everywhere, as Graeme says) but not into the drum.

I hate this job, because I don't understand the components. Haynes tells us to ensure that the paper gasket is at least 0.2mm thick, which surely might undermine the efficiency of the o-ring by reducing the clamping pressure on it. And the last gasket I bought actually overlapped the o-ring. How can that be a good thing?
Nick and Cherry Scoop

Nick, my understanding is the gasket is there to take up any irregularities in the machined faces of the driveshaft and the hub. The O-ring sits partly in a groove and partly proud, thus forming a circular pressure point on the gasket which provides the oil seal. It's a bit like wire-ringing a head gasket.
davidsmith

Hi Nick.

What David says, plus the gasket acts as a sort of shim to ensure the correct clamping of the bearing.

The gaskets in kits I have seen over the past few years are way too thick, which results in a gap between the bearing and the halfshaft once everything is tightened up. This can result in play and wear.

I do a gasket kit with a selection of thinner alternatives in order to resolve this issue.

Give me a shout, chevalierclassics@gmail.com if you want more information, or you can find my kits for sale on eBay.

Cheers,
Malcolm
Malcolm Le Chevalier

Thanks David, thanks Malcolm. Does anybody use sealant?
Nick and Cherry Scoop

I never do. It shouldn't need it if all is well.

Malc
Malcolm Le Chevalier

Nick, in my experience a back seal failure can definitely let oil in to the drum on a Frog.
Simon Wood

X2 Simon
Dave O'Neill 2

Simon, I suppose it could flow outwards along the outside of the hub, and into the drum that way, on the basis that the worst that can happen will. I can't remember exactly how it's put together, but I guess the backplate flange overlapping the drum flange keeps the escaping oil within the assembly?

Well, I'll see what condition the bearing seems to be in, then try the easy fix first.
At home, unfortunately, the car always sits on a cross-slope, so the offside gets a continuous little extra pressure of axle oil.
Nick and Cherry Scoop

Long long ago this was written on our BBS:
Growler, South
And I shall start raving about fully-sealed bearings (you know, the pre-lubed type with integral oil seals)
They're lovely. Last forever and supplement the existing oil seal- no more leaks, and no more damaged bearings from differential metal flakes.
SKF part# 6207zz
NSK part# 6207vvc-mav2


I also use Hylomar blue, on both sides of the paper, and I am not the only one. After assembling it is important to put pressure on the gasket with the wheel nuts (and screw)
Flip



Flip Brühl

I clean the axis end



Flip Brühl

here you see the pressure construction, cut the protruding paper gasket.


Flip Brühl

oooh rear hub leaks. An extremely common scenario round these parts, running wide sticky tyres and driving like a lunatic on track.

I have had a leak from the gasket between the shaft and the hub. As has been said before, the gasket only sets the distance between the hub and shaft, there's an O ring in there that does the actual sealing. I've modified my shafts to have 2 retaining screws into the hub so I can get it proper clamped up - this probably won't work if you still have drums, but as there are 2 retaining screws for the drums that's not so much of a issue. Since that, never had a leak from the gasket. Do it up well tight like Flip says, with wheel nuts.

The hub seal is a different beast though. I'm currently on the fourth major leak (with a variety of effects). Leak 1, hub seal leaked, oil fell out, diff died. Leak 2 all fixed, rinse and repeat. Leak 3, after an upgrade to double bearing hubs (the seal runs in a different location so this requires a thing called a speedisleeve on the axle for the seal to run on) - seal failure - seal replaced by frontline. Leak 4 - as above, but with no obvious failure point this time.

next stop is sealed bearings, then run out of ideas.

Leak 1 is most appropriate to your issue here Nick. Simple failure of the hub seal due to age/tired bearings etc.

For interest, Leak 2 Failure mode was massive loadings into the hub, flexing the halfshaft like a banana and opening a gap between the axle and the seal. There was so much hub flex that the drum was hitting the backplate, and the hub was belting the wheel cylinder. Big leak, oil everywhere, shoes ruined (it was *definitely* in the drum!) and differential blued up and ruined. REar hub bearings (not Malcolms - cheapy cheap ones) also dead after 22 miles.

What you can do to fix that is not to drive as hard. For your car, it'll not likely be managing to corner like mine so shouldn't exhibit such dramatic hub flex.

When you have the hub off, check the axle land carefully with a micrometer for ovality, dents, wear grooves and so on. If it exhibits such features, either a bit of emery paper, or a speedisleeve onto the axle to provide a new surface for the seal to run on. Once you've micrometered the axle you'll know what size to get. Fit it carefully, remove the flange on it (it'll be clear with it in front of you), fit Malcolms bearing kit with his decent seal, and carry on motoring!
Rob Armstrong

Just a thought while discussing oil leaks from axles - check the axle breather is clear otherwise the build up of pressure will force oil past the seals.
Chris at Octarine Services

This thread was discussed between 24/04/2017 and 26/04/2017

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