Experience with oil leak stop additives?

[break23m]

My 3 Litre MK2 automatic is leaking quite some oil. My garage says it's from the end bearing. Replacing the oil seal is a gearbox out job that will take two days. Could an additive like Wynn's Engine Oil Stop Leak be a temporary cure? Any experience here with this kind of additive?
[edit]I had a chance to talk to my Rover specialist this morning. He told me he sells this kind of additive himself. It makes rubber seals to swell a bit. And since the end bearing seal has rubber in it, it might be a temporary cure. I hope so, want to come to Beaulieu in september and I realy want to come there by Rover. [edit]

[lagain]

If it is a rubber seal, the chances are that the rubber is deteriorating, so it is leaking and the best option, unfortunately, is to replace it.
The problem with additives that stop leaks is that they work by bunging things up, which could restrict oil flow where you need it.

[Smallfry]

I expect the bearing is has some play and this will eventually ruin the seal. Replacement will be the best bet by far, as the seal is not really the problem. See if you can move the shaft from side to side.

I have used a Lucas sealer product ( can't remember what it's called offhand) in the power steering pump of a tractor about two years ago, and it worked a treat, and still doesn't leak. I am not sure of how it might affect an auto gearbox though, so I would not try the Wynns stuff, as that's meant for engines.

[enigmas]

I agree with George's assessment of stop leak products for transmissions. Bite the bullet and do the job properly. Band-aid fixes are temporary at best and at worst the product may aggravate the situation and allow decayed seal fragments to circulate with the transmission fluid through the valve bodies and orifices effectively clogging them, leading to other issues.

As an aside a worn "hardened" front pump seal can often groove the nose of the torque convertor creating a small ridge. The fix is to either linish any slight grooving or use a stainless "speedy" sleeve to remediate the scored area.

There's nothing more frustrating than creating a worse situation than you already have.

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Thank you all for sharing your thoughts. I found out that replacing the crankshaft seal is a gearbox-out job, it takes a man who knows what he is doing two days. The engine is running fine, I don't expect the crankshaft bearings to be a problem. So I will give it a go. Hope to tell you soon if it's a succes - or not.

[enigmas]

A bit of confusion here...I presumed that the oil leak was from the front of the transmission where the torque convertor nose drives the transmission pump not the rear main seal of the engine

If you're going to pull the engine/trans unit out as one lump, I'd advise that you replace both the rear main engine seal and the front pump seal of the transmission if an auto. Do remember to lube both seal lips prior to fitting them otherwise you're likely to friction burn the sealing lips once you fire up the engine, if fitted dry.

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The specialist told me the gearbox would have to come out, engine can stay in the car. But a good idea to tackle both if ever it comes to that.