Oil pressure problem C-85

HI Larry,
I think the first thing to try would be a new ball and spring for the oil pressure releaf valve. ............if that fails to help, what you may be looking at is excessive bearing clearance when the engine starts to get warm........and worse case, you could actually have a crack in a web that opens on the oil galley side, releasing pressure in the system.... Higher probability on the excess clearance tho... Of course you have a good idea on how that is going to get fixed.
CArl

What grade oil are you using. I've found that multi-viscosity oils don't work well when oil pressure problems exist. Loosing oil pressure after take-off could be caused by heat changing viscosity, FOD in passages or pump, leaks, oil pump wear are the first things to come to mind. Best to use 100W in C85.

After talking to a company that rebuilds C-85's he plans to now remove the rear accessory plate to see if the problem can be corrected. Can someone tell me, on a 415C is it necessary to remove the entire engine to get the plate removed or can it be done while the engine remains in the plane (big cost difference)? Regards, Larry N3436

The mechanic has checked all you listed Lowell (and others) except the vacuum pressure pad which he will do next. He is trying to fit my plane in between other jobs to help save me money. I'll keep You advised and thanks to all who have replied. Regards, Larry N3436 Tucson, az

What about the oil pressure relief valve on the right side of the case? Could be a bad spring, dirt, etc.
Buzz Dolim

Ask your mechanic how many washers under the press. spring, max allowed
is four (AN960) I always start with two, and then go from there. I like 40+
psi COLD. at idle HOT, should not be below 10 psi.(600 rpm). If all that
does not work, check out the vacuum pad. There is an oil hole and oil comes
from the press. side. The gasket might have blown and dumping press oil
into bottom of crankcase. The last item is to remove the Acc. Case and
check out the oil pump area for groves. Hard to see that happen with a
full flow filter, I have seen it happen with the Screen which only keeps nuts
and bolts from going thru the engine!!