[lostpilot28]

I've looked through the many threads on the front oil seal, but I can't find anything that specifically states what this oil leak will look like. I still have a fine mist of oil that builds up after several flights on the engine.

Mostly it settles toward the bottom of the engine...but I've noticed that I get some oil pooling in the inlet rings (SJ cowl). It collects apparently inside the plenum toward the front and over time runs down to the inlets. Maybe a teaspoon at the most after a one hour flight and several days of sitting in the hangar.

I've tightened up all the loose nuts, bolts, hoses, clamps, etc. But I started thinking that maybe it's the front oil seal. I only see a very light mist on the back of the crank flange and flywheel. No drips in that area, although I do see some collecting on the starter and alternator.

Any ideas?

 

[jbDC9]

Any ideas?

Oh yes please, I'd love to hear some ideas on this. I've been dealing with the same exact annoying leak(s) on my engine since day one. I've even replaced the front crank seal twice with no effect... I tightened everything down that I can find, even fiddled a bit (lengthened and re-aimed) with the crankcase breather tube. It's still is a wee bit drippy with 730 hours on it. Consumption seems normal though, usually 10 hrs/quart.

Maybe it just wants to be a radial engine when it grows up?

 

[molson309]

Are you using a CS prop by chance?

If so, check that you aren't getting oil past the O-ring that seals the prop to the crank flange. On my RV-7A I had a slight seep through this O-ring, and instead of pushing oil past the prop-to-flywheel flange, it came out on the backside of the flywheel, and got spun in all directions from there. I thought it was the front seal at first but that was dry. Later I discovered oil on the backside of the flywheel and finally figured out where the oil was coming from. Changing the O-ring inside the propeller hub (Hartzell CS) and making sure the flange seal was clean and not nicked solved the problem.

It never seeped all that much oil but I usually found it, in my case, on top of the FAB on my IO-360 (parallel valve, updraft FI in center of oil sump). There was also oil splattered around the front of the engine. A sign it's coming from the prop is that the oil is unusually black; the spinning crank with oil injected into the hollow at the center is an efficient centrifugal separator.

Mark Olson N407V RV-7A
N16XV F1-EVO

 

[jbDC9]

If so, check that you aren't getting oil past the O-ring that seals the prop to the crank flange.

In my case, yes a C/S prop, and no I hadn't thought of that seal. Both times when I had the prop off to replace the crank seal I checked the mating surface and the O-ring and lubed it with DC-4 before putting the prop back on, but who knows, perhaps it has a tiny imperfection in it. One more thing to check out... thanks!

 

[lostpilot28]

Mine is a catto 3-blade, fixed pitch prop. I'm just wondering if there's a sure-fire way to determine if it's the front seal that's leaking.

 

[Frank Smidler]

oil with front seal leak

When my front seal was leaking the most notable indicator was drops of oil at the bottom of the starter and alternator. I also had pooling on top of the air box but this could happen with other types of leaks as well.

 

[Walt]

In my case, yes a C/S prop, and no I hadn't thought of that seal. Both times when I had the prop off to replace the crank seal I checked the mating surface and the O-ring and lubed it with DC-4 before putting the prop back on, but who knows, perhaps it has a tiny imperfection in it. One more thing to check out... thanks!

'O' rings should always be replaced whenever a unit is dissassembled, this is especially true for the ones that take hours to replace if they leak (like the prop)! That can be an awful lot of work to save $1.75

 

[painless]

My midtime engine sat for a year and a half and upon first running it, my front seal leaked momentarily. Happlily, it stopped after running the engine. It presented as a fine spray of oil on the inside of the cowling in the approximate location of the front seal.

YMMV.