The Stovebolt Site Forums The Shop Area Engine Shop Somewhat odd oil leak

My 49 3100 has the original 216 that I got running approx 6K miles ago. It's running surprisingly well for an engine that sat for 45 yrs...
The bottom end is the same as when I got it (odometer shows 99K miles) but I had the head rebuilt to get it running. It has a bypass oil filter also.
Once I got it running I settled on 15w40 oil.
It's leaked out of both ends since I got it running.
With warmer temps I noticed my oil pressure running lower (around 13-14 psi at speed, perhaps 5 at idle. During the winter it would pump upto 30 when cold, now it barely reaches 15), so I decided to drop the pan and have a look see.
The pickup screen was alittle clogged but other wise the oil pump looked OK
I dropped the main bearings and plastigauged them and got .0025-.003 between them. There were no shims so I put them back as is. While I had the rear out I went ahead and installed a new rope seal in the bottom but decided against dropping the crank to replace the top.

Long story short.
With new pan gaskets the front barely leaks, only a couple drops at shutdown but the rear leak has changed.
Now it only leaks at idle. I can see a slow drip, drip, drip at idle but when I give it any rpm above idle the drip stops. It barely leaks at shutdown if I don't idle it long before I shut it down.
I don't know but I find that sorta odd. I'd think w/increased oil pressure it would drip faster instead of not dripping at all.
I just changed the oil to 20w50 to see if the oil pressure would increase and the results are neglegable but it did seem to slow the drip out of the rear.
I'm leaning on going back to 15w40 on the next change as I didn't see any increase in oil pressure and the oil is much cheaper.

Is it odd or SOP for these Stovebolts?

Dave

Oil pressure does not cause leaks. Once the oil escapes the restriction of the bearing clerarance, gravity takes over and the oil drips back into the pan. Unless there's a scratch in the bearing that squirts a stream of pressurized oil right at a seal, I can't see where oil pressure would change the rate of flow of a leak.

The rear of the crankshaft has an oil slinger built into it, doesn't it? Sometimes the drain channels between the slinger and the seal get clogged with sludge and the oil overwhelms the seal rather than draining away. Some crankshafts also have a spiral groove that pushes the oil back in the direction of the crankcase that can get clogged up amd cause a leak. Good luck!
Jerry

The increased centrifugal force from the spinning crank throws the oil away from the seal.

Good to see you posting again Jerry, hope all is well with you and the Gold Wing.
I did notice a drainback hole in the bottom of the rear main cap and it wasn't clogged. There was a slight wearing away of the top babbitt coating at one small corner of the rear main but otherwise the rest of the bearing looked good. The crank also looked good with no discernable ridges or scratches.
If the engine makes it to the winter I'll be hitting a crossroads of sorts, rebuild it or go for some more performance...
I'm just enjoying the cruising too much now to take it down
You still wanna get rid of one of your late model 235's?

Jim, that does make alot of sense and could be the reason.

The oil pressure you quoted is excellent for a 216. You don't have oil pressure problems for sure.

Jerry,
it is good to see you back online. We all wish you a speedy recovery although you seem to have that mastered!

Fred