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MG MGB Technical - Half-shaft oil leak

I've got an oil leak problem on one of the rear axle half-shaft seals on my '73 BGT. The seal was replaced in January and again I replaced it in June of this year as it was still weeping. I now notice it's leaking again.

The car has only 33,000 miles on the clock and the transmission is otherwise quiet and clonk-free. Is there likely to be a problem with the half-shaft that's causing this and if so what's the most cost-effective way to resolve this - replacement half-shaft or complete replacement axle? I've read elsewhere an axle oil leak can also be caused by a blocked vent - how likely is this and where do I find this vent?

Thanks in advance for any help or advice.
Mike

The vent is a mushroom type device on the top of the axle tube near the diff.

Is the leak coming from the seal or is it getting through the coned collar - I always refit the collar using Loctite to ensure it is oil tight.
Chris at Octarine Services

You may need a new collar e.g. http://www.leacymg.co.uk/index.php?product_id=538322&option=Prod_detail&category_id=88208 as well as seal as the lip of the seal runs on the collar not the half-shaft. The end of the collar is pressed up against the inner of the bearing by the hub being tightened down onto it so it shouldn't really leak past it unless the face of the bearing or collar is damaged.

The vent is on the right-hand side of the diff. Some years ago a friend with a TVR had a long and messy court case with his dealer when TVR started fitting non-vented vents (I kid you not) that blew the seals, lost the oil and wrecked the diff and bearings. There was a recall, but his dealer hadn't done the necessary.
Paul Hunt

Yes - it shouldn't leak but sometimes they do - whether damaged or not sufficiently tightened (have found hubs nuts loose!)
Chris at Octarine Services

Thanks Chris & Paul. I'm thinking it might be the collar seal as this has a lot of surface rust on it from where the car has been stood for so long without movement. It didn't appear too serious, but I suppose it's possibly enough to abrade the inner seal lip

I think I'll order a new cone & seal and give it another go this weekend.

Cheers.
Mike

Well hopefully it's sorted now. I've fitted a new cone and seal, it looks like riust pitting on the old cone was probably the problem.

Here's the leaking seal as it was, clearly leaking from the inside mating surface:

Mike

...and here's the condition of the cone that was removed. the pitting is actually only along an inch or so of the mating surface but this was at the bottom of the cone which is why I overlooked it previously. I guess it was on the lower edge as this would have been where moisture collected whilst the car was stood for so long. The pitting is actually up to .5 mm deep from a visual inspection so it's not surprising it caused a leak. I checked the breather and this seems to be clear and there's no oil leak on the other side of the car.

Thanks once again for your help chaps, I'm fairly confident this will now fix the problem.

BTW Paul, I ordered the part from Leacy MG as they came out a at least £3 cheaper for the cone that other suppliers, their service was excellent too. £24.38 for the cone and a new seal including next day delivery. Can't fault them!

Mike

If you hadn't driven the seal so deep in the casing it probably wouldn't have leaked! Normally the seal should sit flush with the outer end of its recess.
Chris at Octarine Services

Oh yes, that cone will leak, well pitted :o)
Paul Hunt

Chris, I don't see how the seal can sit flush with the outside of the bearing cap as the cap has a lip which is there to presumably stop the seal from popping out. As it is the seal seems to sit squarely on the rim of the sealing cone and is tight in the bearing cap.

Haven't done many miles so far, but so far it seems to be oil-tight.
Mike

Flush with the outside face of the cap is how I found and replaced mine on two axles:

I don't think it's an issue, just that the previous seal may have been running on a good part of the collar had it been flush instead of recessed.

Paul Hunt

Should be no lip - seal sits flush with the end of the cap as per Paul's pic.
Chris at Octarine Services

This thread was discussed between 14/10/2009 and 21/10/2009

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