427 Oil Leak Mystery

[Paul Sutphen]

STARLINER,
I spoke to Dave recently and after trying several fixes he's come to the conclusion like yourself that the block is faulty and will be replaced. Thanks for the insight and suggestion. Everyone has been very helpful.
Paul

[Cobranut]

Paul,

Check the tapered pipe plugs on the back of the block.

I had a pesky leak on a C-Series Cummins in my motorhome after replacing the head. There was a 1/16" npt oil gallery plug in the rear of the head which leaked in a steady stream when under pressure.
I pulled and replaced the plug numerous times with different sealers and it still leaked. I was concerned that the new head had a hairline crack at the hole, as the tighter the plug was torqued, the worse the leak. (If you've ever swapped heads on a large diesel in a pusher motorhome, you'll understand my reluctance to having to swap the head again.)

I finally got a 1/16" pipe tap, coated it with grease, and chased the threads. Then I flushed it out by cranking the engine over until I got a good flow of oil out the hole and reinstalled the plug w/sealer. No more leak.

Good luck,

[ERA Chas]

Cobranut,
WHICH BRAND SEALER?
Thanks,

[Cobranut]

Chas,

I used standard pipe thread sealer with teflon, which is what I use on most pipe thread fittings.