Help with low oil pressure

[rebelflier]

I have an RV6 with O-320-E2C 150hp with approx 100 hrs ( I am not the builder ). The oil pressure has always been high on start up with Aeroshell 100. I would have to let the engine warm up for up to 10 min to avoid over pressure on take off. after it warmed up it would run around 80psi at cruise. oil temps never over 190. I recently change the oil and went with Phillips 20W50 and a Kelly oil filter instead of Champion. Then the pressure would start dropping at about 150 deg until it got to 60psi at 180 deg. I have installed a new spring, added washers, new ball and dressed the seat on the pressure valve. After no luck in getting the pressure back up, I decided to drain the oil and the filter and go back with Aeroshell 100. My pressure is still high on take off but it still drops as the vernatherm valve closes. My last test flight the oil temp was 175 deg and mid 60's on pressure, OAT 95 deg. I have the NDM 20002A Cooler and the vernatherm valve says "Superior" on it. Could the problem be with the Kelly oil filter? Or is the Vernatherm valve not working properly? The highest temp I have seen was 190 deg with OAT of 100, full fuel, and 2 heavy guys climbing out after refueling. I am going to check the gage today. Another thing that is puzzling is that when you bring the power back the oil pressure goes back to 85 psi. I can do a ground run up with engine hot and the pressure drops back to the 60's at full throttle. Any suggestions Please.

[DanH]

<<Could the problem be with the Kelly oil filter?>>

Sure is easy to swap for a Champion and find out. Report back please.

<<Or is the Vernatherm valve not working properly?>>

Unlikely to have any effect on pressure.

<<I am going to check the gage today.>>

Always a good idea.

<<Another thing that is puzzling is that when you bring the power back the oil pressure goes back to 85 psi. I can do a ground run up with engine hot and the pressure drops back to the 60's at full throttle.>>

Interesting. First thing to mind is a partial inlet blockage, something like rag fuzz on the screen. However, if true it should have done the same with the Aeroshell 100. Did it?

[frankh]

I'm not sure anything is rong at all.

So the Aeroshell 100 is a "straight" 50 oil..That means its thicker when cold than a 20/50 multigrade. From memory a 20W50 acts like a straight 20 when cold but only thins to act like a 50 when hot.

As you only have a 20 psi difference between the two oils in cruise this would seem reasonable.

I'm not sure whats wrong with 60psi in cruise..I thought the limits were a minimum of 25psi..Not sure I see what the problem is..I'd just select the oil you like and stick with it.

I run aeroshell 100 and it runs around 60psi in cruise.

I doubt the screen is blocked as the oil pressure would drop sharply on take off..but if it has not been checked in a long time It would be worth pulling and cleaning it.

Frank

[Mike S]

Originally Posted by rebelflier

Another thing that is puzzling is that when you bring the power back the oil pressure goes back to 85 psi. I can do a ground run up with engine hot and the pressure drops back to the 60's at full throttle. Any suggestions Please.

Ron, first off, welcome to the force.

Second, from the above quote-----loose wire or bad sending unit comes to mind. Also, relief valve opening too much -----if such a thing is possible.

Good luck.

You might contact Malon at Mattituck.

[rebelflier]

Dan,
Thanks for the response.
I will have to order a new filter to try it.
My question with the vernatherm is the fact that I have plenty of pressure until it starts closing. You can watch the pressure drop 10 psi in a mater of seconds after it reaches 150 deg. I just pulled it out and it looks new.
I read the other threads on oil coolers and saw that certain ones had some pressure drop conserns. I thought maybe that could be it.
As far as the screen goes it only had a little carbon on it after 40 hrs. and I checked it again after I switched back to Aeroshell ( it is clean ).
I never noticed a drastic pressure drop before I changed the oil. Maybe I am paying more attention after I changed it. I would really like to get the pressure back up in the 70's before Oshkosh.
Going to go check the gage now.

[rebelflier]

Thanks everyone for the input!
I temporarily installed a cheap mechanical Autozone oil pressure gage in my dummy light sending unit hole. It is very responsive. During the test flight after 150 deg it dropped just as the electric one, but it has a strange fluctuation, between 50 and 65 psi. After I landed with the oil temp at 180 deg I did another run up and the mechanical gage jumps between 60 and 80 psi. Is this normal? I think the electric one must average it out.
When I power back down the pressure stabilizes around 80 psi.
Some of you say 60 psi is fine but this fluctuation puzzles me.
Thanks again,
Ron

[rvbuilder2002]

Originally Posted by rebelflier

Dan,

My question with the vernatherm is the fact that I have plenty of pressure until it starts closing. You can watch the pressure drop 10 psi in a mater of seconds after it reaches 150 deg.

Your above statement would make me suspect it is something related to the oil filter. When the vernatherm is open it provides a bypass for the oil cooler. This same bypass is also a bypass route around the oil filter (cold thick oil wont flow through the filter very well). Once the vernatherm closes the bypass, all oil must go through the filter and oil cooler.

I suspect if you change the oil filter the problem will go away.

Edit: Many years ago I had evaluated the oil path in a Lyc and have believed since that the above statement (in blue) was true. DanH questioned the accuracy and did some research which makes it sound like it is not correct. I still plan to look at it again when able but for now this statement should be considered incorrect. S.M.

[rebelflier]

Thanks for all the help,
I added one more washer and got the pressure stabalized at 68 psi at 2400 rpm and 180 deg oil. I suspect the Kelly oil filter is a little more restrictive than a champion, which would explain the pressure drop. I will go back to Champion next oil change and see what happens. Hope to see some of you at Oshkosh.
Ron
RV6 N68AD (needs paint)

[131RB]

Quick question, who did the overhaul? Sometimes when the case is reworked the shop will do a service bulletin on the oil pressure regulator valve seat. If you dont have the right oil pressure regulator cap the ball will continue to roll off of the seat as pressure builds causing a continuos fluctuation in oil pressure.

As far as constant oil pressure goes, its normal for oil pressure to be higher when the engine is cold and for the pressure to drop off some as the engine gets hot.
Ryan

[rebelflier]

This was a new engine that was pickeled at about 30hrs after aircraft was destroyed in a storm. It has the short stack on the oil pressure relief valve. I will check on the service bulletin.
Thanks,
Ron