Rear Crankshaft Oil Seal Query

[david.g.chapman]

Last autumn a year ago I pulled the engine and changed the rear crankshaft oil seal, among other things like a new clutch.
Unfortunately I forgot to lubricate the oil seal prior to running the engine and there has been a small to medium engine oil leak coming from the bellhousing throughout the summer. Hmmm - must be the oil seal.

One year on I'm feeling keen and have decided to pull the engine again and set things right. I've reached the stage of removing the starter motor and the separate plate (for my Mk2 twink), so I can see the back of the flywheel. There is no sign of oil on the flywheel (it looks dry and clean), but I can see oil lining the inside of the bell housing, probably supplying the leak as the engine runs. There is no oil leak above the bellhousing at the back of the engine and head.

My question is - for a leaking oil seal, is oil thrown onto the inside of the bellhousing without touching the flywheel? Or does it just trickle down from the bottom of the seal?
Also, is there anything else at the back of the block covered by the bellhousing that could be the source of the leak?

Dave Chapman.

[types26/36]

Also, is there anything else at the back of the block covered by the bellhousing that could be the source of the leak?Dave Chapman.

Left lower bell-housing to gearbox bolt (viewed from front) can leak if not sealed as it goes into the gearbox while the other three are “blind holes” but doubt the oil would be thrown about as most likely to trickle down.

[david.g.chapman]

Yes. I suppose the oil could just trickle down to the bottom of the bell housing and wick sideways up the sides as well as dripping out the bottom.

I was wondering about that penetrating gearbox bolt, but it looks like engine and not gearbox oil. I might find out more when I pull the engine but the back of the block is likely coated in oil. I'll just change the seal, check for any grooves on the crankshaft seal surface and check any oil gallery plugs etc.

Cheers,

Dave Chapman.

[miked]

Smell it!

[david.g.chapman]

Ah! The sweet smell of sulphur! That means you have gear oil. A good tip!

[elancoupe]

Check carefully that your cam cover isn’t leaking at the back. I had a regular puddle under the bell, and I was convinced that it was the rear main. In fact it was the cover gasket.

[miked]

I agree with Mike. I have encountered that several times. Curtaiining down from the cam cover. I concluded it was not the rear oil seal as the back of the flywheel was bone dry.

[david.g.chapman]

Thanks for the heads up, but I checked above the bell housing and the cam cover, head gasket and rubber oil transfer tube are fine. So the leak has to be coming from inside the bellhousing?
Slightly surprised that the back of the flywheel is dry, but I'm holding on the the oil trickling down theory.
I will have one more brainstorm to find another source for the leak, then I'll pull the engine. I'm nearly at that point anyway.

Dave Chapman.

[rgh0]

A cheap borescope should be able to examine inside the bell housing to tell where the leak is coming from.

cheers
Rohan

[2cams70]

Suggest you remove the backplate lower inspection cover and have a look. It's held on by a couple of small easily removed bolts. You could even have a look with the cover removed and engine running to see if you notice anything dripping.

Note that if you smell sulphur in gearbox oil then you are using the wrong gearbox oil. There will be a difference in the odour between engine and gear but it should not be the strong smell of sulphur.

[h20hamelan]

Did you use some small amount of thin sealant around the outside or rear main?

[david.g.chapman]

Thanks for your replies.

The gearbox oil is the right GL4 spec. Just a slight sweet "sulphurous" (to my mind) smell.

A bit of history... After replacing the seal last year, after only about 50 miles the leak was apparent, 3 or 4 drops per trip of 40 miles after leaving the car. With the engine running, there is one drop of black oil falling about every 80 seconds. This has remained consistent over the year and 1500 miles.

I don't understand the comment about the main bearing. This could be important - can you expand h20?

Dave.

[mbell]

It could also be the sump gasket, or crank bearing carrier and block gasket.

I ve been trying to deal with leak in this area. Looked at it with a scope and no oil on flywheel. Done the sump and cam cover gaskets which think have improved it, but still leaking.

Imo it's live with it or pull engine.

[david.g.chapman]

Found a link on the main bearing.....

viewtopic.php?f=39&t=51001

It could be the oil seal carrier leaking...I will check.

Thanks everyone. After 20 years as a member this forum continues to deliver!

Dave Chapman.