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MG MGB Technical - to replace rear oil seal

hi
79 MGB

leak in rear oil seal, the one you get to after you remove the rear wheel, drum,brake shoes----

according to haynes mgb workshop manual the seal would be part # 43, page 144.
moss motor catalogue lists it as #89, part #120-700.

i think i am correct in identifing it.
but asking for verification before ordering parts.

if you have any helpful hints on how best to do the replacement job, please pass them on.

thanks !!

john

john sutter

Hi John,

Try your local bearing shop for a replacement. Take your old ones with you.

Herb
Herb Adler

That's the correct part, in both cases.

Remove the shoes and handbrake cable. The hub is a tapered fit onto the half-shaft so will either need a puller, or you can use wedges between two opposite backplate bolt heads and the back of the hub, once the hub nut has been slackened. This is done up to 170 lb ft so can need a pretty serious breaker-bar to shift. Both sides on the Salisbury/tube axle are conventional i.e. right-hand threads. For Rostyle wheels remove the centre cap and replace the wheel, for wire wheels just remove the spinner, and jack the tyre back down onto the ground. That way you are using the weight of the car to hold the wheel from rotating as you undo the nut. The nut itself is 1 5/16" AF (same as for the crank pulley nut), a 33mm socket may fit. If you have wire wheels then you may find a 3/4" drive and/or impact socket won't fit inside the hub. I bought a 1/2" drive non-impact off the shelf and that fits fine, that is 1.73" outside diameter and the ID of my hub is 1.863".

Raise just the corner you are working on so (hopefully) oil doesn't run out of the axle once the bearing cap is off.

With the hub off remove the back-plate by undoing the four nuts and bolts. You *may* find you can move this out of the way with the brake pipe still attached, but you may need to disconnect the pipe from the slave. In that case put a hose clamp on the hose (single hose for both sides between axle and body) to minimise fluid loss and air ingress. With the backplate out of the way the bearing cap that holds the oil seal is exposed. This has a short length of interference fit to the bearing outer. You may be able to drift the cap off if you have some handy notches around the join, if not replace the hub loosely and use a mallet on the back of the hub to start pulling the half-shaft and bearing. This will open up a gap and allow you to drift the cap off the bearing, but if you can do that without disturbing the bearing in the axle casing so much the better.

With the cap off carefully inspect the surface of the collar (this has the taper that the hub locates on towards the outside) that the oil seal runs on. If there is any damage the collar should be replaced. This is just a push-fit onto the half-shaft, seating against the bearing inner.

Replace the oil seal in the cap, grooved side facing the bearing, flat side facing out. Grease the lip of the seal, even though it will be running in oil once under way. Refitting is the inevitable reverse of removal. Tighten the hub nut to 170 ft lb and the nearest split-pin hole. If you disconnected the brake pipe have someone apply light pressure to the brake pedal once you have the bleed nipple open *before* you remove the hose clamp so any air doesn't run back up the pipe.
PaulH Solihull

This thread was discussed between 15/07/2011 and 16/07/2011

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