Rear Main Oil Leak

[SimonBrown]

My S2 OTS has been plagued with an oil leak from the rear main for years now.
It leaks only when thoroughly hot after a motorway run but is dry in normal day to day use.
The crank has been ground to fit the Terrys oil seal conversion, and checked to be dimensionally correct, also fitted with a new Terrys seal, still the leak persists.
I have always run it with a quality 20w50 oil

I have checked actual oil pressure at motorway speeds and for crank case pressure. It does not appear crank speed related as it will start to leak after about 20 mins constant speed driving at 50-60mph.
As the leak only starts in these conditions (and to avoid pulling the engine again and obtaining another crankshaft) would anyone have any suggestions?

Would it be worth trying a 20w60 oil that may remain more viscous at higher temperatures?

Appreciate any help

Simon

[abowie]

No harm in trying, but it probably won't work.

Regardless of what rear crank seal option ( factory, various "upgrades") some cars leak.

As long as it's tolerable I'd leave it alone.

[mgcjag]

Hi Simon...are you really sure its not the rear sump seal..endoscope in the bellhouseing to see oil down behind the flywheel...and double check you oil level...drain and refill with a measured 8.5lit...youv probably done all this anyway....Steve

[swindler]

Check your breather assembly isn't blocked

[mtnjag]

Per mgcjag - you sure it’s not the rear sump seal? Mine was.

[bitsobrits]

Have you also ruled out leaks at the banjo bolts (cam oil feeds) running down the back of the block?

[SimonBrown]

Checked cam feeds, crankcase pressure and thank you.
It is possible it is sump, but I assembled it very carefully with new gaskets, seal and sealant.No change in symptoms since before stripping.
Today, I have used Talcum Powder to cover the inner flywheel face, and all accessible areas at the rear of the engine. I then ran it for around 45 mins at varying speeds including stationary at 2500rpm for 3 minutes.
After all this it is bone dry, not even the start of a leak.
BUT, If I take it for a gentle motorway run for half an hour, at 55-60mph it will then leave a puddle on the floor of around 15cm and be all over the exhaust.
Very frustrating!
Simon

[mtnjag]

If it is a rear seal leak the oil will be spun off of the flywheel from the center. Dead giveaway.
A rear sump leak will not exhibit in that way.
You should be able to see that area through an inspection hole.