Rear hub oil seal problem

[alex_holden]

Fenchurch's rear nearside hub oil seal started leaking badly at the weekend and soaked the shoes. I bought a pair of hub rebuild kits (bearing, seal, gasket, O ring, and washer) and fitted them on Tuesday night. There was no discernible groove worn into the stub axle, just a smooth shiny band - I tried rubbing my fingernail across it and couldn't feel any kind of a step or bump. I also checked to make sure the breather wasn't blocked. This morning I discovered that both sides have started to leak, the nearside worse than the offside. Luckily I caught it before the new shoes got wet.

The first problem is that the halfshaft gaskets don't seem to have sealed properly. If I look carefully I can actually see a slight gap between the halfshaft and the hub even though the shaft is screwed down tight. I noticed when I fitted them that the paper overlapped the O ring but I didn't trim it back because I figured it must be deliberate, but now I'm wondering if that might be what's stopping it clamping down properly.. The old gaskets were ones I made myself from thick gasket paper and they sealed fine, but I did apply a film of liquid gasket to both sides to assist the seal (I didn't bother this time because it made them harder to remove).

The second problem is I think the nearside seal is probably still leaking and I suspect the offside one might be leaking slightly too. It's a bit hard to tell whether the oil is coming from the halfshaft joint or the seal, but I don't see how oil from the halfshaft could make it to the backplate.

Any suggestions what I should try next? Is it worth trying to replace the seals again (because if so I need to get the order placed ASAP)?

[bmcecosse]

Sure the axle isn't overfilled with oil ? Otherwise - I would revert to your old way with thicker gaskets and some goo - it worked!

[IslipMinor]

Alex,

Have you fitted the wheels and still got a leak? The wheel studs clamp the half shaft up tightly.

[alex_holden]

Sure the axle isn't overfilled with oil ? Otherwise - I would revert to your old way with thicker gaskets and some goo - it worked!l

I filled it to the bottom of the level plug. I'm sure I can fix the problem with the half shaft gasket as you say but I'm more worried about the seals.

Incidentally the diff input seal has developed a slight leak too but I'm not too bothered about that for the time being.

[alex_holden]

Have you fitted the wheels and still got a leak? The wheel studs clamp the half shaft up tightly.

Yes, I only noticed the leak after driving it for a couple of days. There's oil both on the backplate and the front of the drum so I think both the halfshaft gasket and the seal has been leaking.

[Orkney]

If you make a thick paper gasket you can apply with a brush a few good thick layers of instant gasket and let dry before fitting - so long as the coats are relatively evenish it compresses nicely and doesnt present a problem for removal at a later stage.
(obviously only any good for upto low or no pressure seals)
Works a treat on flattened cork rocker cover gaskets when applied as a bead and let dry - maybe not a long term fix but liquid gasket is a toolbox must have - hylomar blue takes some beating !

[DaveC]

Is the axle air breather clear Alex?

[alex_holden]

Is the axle air breather clear Alex?

Yes, definitely. I even unscrewed it from the axle casing so I could have a closer look at it .

[Willie]

The thickness of the halfshaft/hub flange gasket is very important as its job is not only to seal the joint but also to ensure that the outer of the hub bearing is firmly clamped. If the rubber ring is fitted correctly there is no way that oil could escape past it unless the half shaft is not securely clamped in position. with the drum off there is only the single screw holding it and, if it is not tight you could get a leak
but then refitting the brake drum will add another two clamping screws.
When you fit the road wheel you clamp it even more securely. There was no noticeable wear on my axle when I replaced the inner oil seals but it persisted in leaking until I fitted new one about 1/16" proud of their original position. i.e. they are running on a virginal area of the axle.

[alex_holden]

The thickness of the halfshaft/hub flange gasket is very important as its job is not only to seal the joint but also to ensure that the outer of the hub bearing is firmly clamped. If the rubber ring is fitted correctly there is no way that oil could escape past it unless the half shaft is not securely clamped in position.

Do you know if it's correct for the gasket to overlap the O ring? I think the ones I made myself didn't but the ones that came in the hub rebuild kit do. You would have thought the new gasket would be the right thickness. The manual quotes a figure for how much the bearing is supposed to be proud of the hub surface - I'll try measuring it when I take them apart again tonight.

There was no noticeable wear on my axle when I replaced the inner oil seals but it persisted in leaking until I fitted new one about 1/16" proud of their original position. i.e. they are running on a virginal area of the axle.

Aha. I'll try that. I'm hoping it'll be possible to move the seals I just fitted without damaging them, but if not I ordered another pair today. Annoyingly I actually considered assembling them like this when I changed the seals but decided not to bother because the shafts didn't appear to be worn!

[dunketh]

Do you know if it's correct for the gasket to overlap the O ring?

This is not correct and I'll bet you a pint is the source of your problem.

The rubber can't make a tight seal between the metal parts if there's a bit of paper in the way. Paper wont compress the same way as rubber.

Time for some blue-peter scissor-alteration!

[Willie]

Well, I may be going senile but as I remember the gasket DOES overlap the rubber sealing ring.

[bmcecosse]

Not entirely sure you are supposed to use both gasket AND O ring. Is the O ring not a later improvement that was instead of the older gasket idea ?

[Willie]

Yes, the o ring was added to the gasket on later cars and can only be retro fitted to earlier cars if the later hub is also fitted.

[alex_holden]

There's definitely an O ring groove in the hubs. I decided to wait until the new seals arrive before dismantling them again because I suspect I probably won't be able to get the nearly-new seals out without damaging them.

Personally I think not overlapping the gasket and the O ring seems to make more sense.

[dunketh]

Well, I may be going senile but as I remember the gasket DOES overlap the rubber sealing ring.

I had both paper and O ring gaskets. The gasket doesn't overlap.
Of course they could have been DIY'd from gasket paper in the past.
Pint bet's still on though.

It makes sense not to overlap. Paper and rubber would compress at different 'rates' if thats the right word.

[Willie]

You owe me a pint then. I have just checked my new spares kit and the gasket DOES overlap the rubber ring. Thank god I'm not yet senile!
I think that on early cars they found that the gasket alone was not good enough, especially when the drum was removed which left the joint relying on one little screw. Adding the O ring together with the gasket gave some resilience to the joint since the springiness of the rubber would have a limited self sealing effect. There should be a paper gasket as well as the O ring and there should be no need for any gasket goo.
ALEX, very sensible to wait for new inner seals you wouldn't want to have to strip it all down again.

[alex_holden]

But were the original gaskets like that on the O ring equipped hubs? Maybe the current pattern gaskets are designed to overlap so that you can use them with the early hubs too. I'm still not sure why mine leaked but I plan to use plenty of gasket cement when I put them back together - belt and braces.

[dunketh]

You owe me a pint then. I have just checked my new spares kit and the gasket DOES overlap the rubber ring. Thank god I'm not yet senile!

The bet was based on whether removing the overlap cures the leak on Alex's car. That said I'll be at the bar at next years national.
I would 2nd your advice about not using blue toothpaste - it does make a terrible mess of things.

[alex_holden]

It didn't make a terrible mess the last time I used it on the hubs; the only reason I didn't bother using it again was because it glued the halfshafts to the hubs and made them a bit more awkward to remove.