I've had a reoccurring oil leak from the rear main oil seal on the new race car's engine. It happened when I first built the engine and that turned out to be an issue with the cover that the oil seal sits in not having any sealant (my bad!) and I had used a GSF oil seal.

I sealed the cover properly and put a Payen oil seal in and it seemed fine. Then on the dyno yesterday it started to leak from somewhere up there again (haven't had time to get the gearbox off yet).

Any ideas what it could be? I've got Pug and Payen oil seals on the way again in case something is wrong with the existing one but want to make sure I've got all parts ready for the weekend as I'm supposed to be on a trackday on Monday!

When fitting the oil seal I use the fitting cone and put a bit of oil around the outside of the seal then slide it on flush with the crank / block.

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Rallye Race Car

Good point, should order some genuine ones of those as well

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Rallye Race Car

My Dad took the gearbox out yesterday and had a look. The rear main seal basically fell out and we found some gunk behind it, also noticed a score mark of some sort on the crank. Looks like it was the main after all. Put it all back together again and will see how it goes on the trackday on Monday.

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Rallye Race Car

It looks like a mark from where someone has tried to remove the oil seal before, it's not a circular line around the crank. I've smoothed it back so hopefully it doesn't cause any issues in future.

Would like this engine to stop leaking oil!

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Rallye Race Car

Its pretty obvious when you take the bearing cap off Dan, but as others have said, don't rely on the seal alone, get some decent sealant on all the mating surfaces too. Also, my Longman engines have had an round alloy spacer that goes in behind the main crank seal. Its clamped by the bearing cap and I think its there to stop the seal sitting too far back in the cap. I'm not convinced it's essential, just make sure the seal is sat fairly flush with the end of the crank, and a bit of sealant around the outer edges of the oil seal never hurts either!

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Oulton Park in a BTCC 306 vid 1
Oulton Park in a BTCC 306 vid 2
Lap of the 'ring

Yep, quite a common thing.

Proper pain to do right, make sure when you fit them to leave 2mm proud when you cut them down.

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"Supercharged - 454.1bhp/317.5lb/ft"
Peugeot 306 GTi-6
2000 (X), Moonstone