oill seal keeps blowing

Phatman 20 years ago

The crankshaft oil seal on my bro's bus keeps blowing, we're not sure why. The engine, a '74 tp, is in good condition, no blow by, breather pipe is clear and pressure relief valve moves freely. After 3 years of perfect running it's blown 3 in as many months! We've tried black German seals, red Mexican, and now a red German seal (which looks the best of the lot). We've seated the seal all the way back and also flush with case...someone suggested the crankshsft maybe worn oval? Any ideas are welcome now! It's leaking from the inner flywheel bit.

TIA

--Steve

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Speedy Jim 20 years ago

First step: Measure the crank endfloat. Max. spec is 0.15 mm If your play is *much* greater (such as 0.3 mm), the oil seal will not function.

Examine the crank sealing surface closely. It should be mirror-smooth. If you see tiny grooves in the surface, they will destroy the oil seal in short order.

Speedy Jim

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Crusader george 20 years ago

and when installing a new seal, coat the inner lip with some oil. I had a similar leak once , turned out it wasn't the seal, but the block was cracked around the third cyclinder area.

Good Luck !

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Phatman 20 years ago

Hi, engine has no end float, it's a genuine low milage unit. I smeared oil on the lip before fitting this time and fingers crossed it seems to be ok so far. Last time we drove 70 miles on the motorway before it failed on a long hill. I did notice a tiny nick on the flywheel edge which I carefully smoothed and polished off - although I don't think it touches the seal. Anyway, time will tell!

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