rebelflier

rebelflier

Member
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.
 
<<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?
 
OK

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
 
Welcome to VAF!!!!

rebelflier said:
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.
Click to expand...

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.
 
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.
 
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
 
rebelflier said:
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.
Click to expand...

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.
 
Last edited:
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)
 
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
 
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
 
<<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.>>

Ron, no it isn't normal.

A few days back I told a story about ignoring warning signs. A few days before that we all agreed to tell a fellow straight if we thought he was gonna bust his butt.

You made two changes, oil type and filter. Swap the filter before you go anywhere and see what happens.
 
If it's the filter, allow me to suggest....

Ron:

If you change the filter and that remedies the condition, please don't discard or disassemble the old filter. Rather, please consider sending it intact to the manufacturer or an engine-builder-experienced member of this forum who will dissect it and analyze where the problem lies.

Perhaps there's something to be learned that can benefit the entire community or maybe it's just a one-off problem. Either way, an analysis by a third party would be of significant interest to all of us.

Thanks.

Barry
Tucson
 
Dan,
The first change I made after the initial pressure drop was to the pressure relief valve. So there were three changes. Yesterday I took the washers out and put in a shorter spring just to see what happened. And as expected the pressure dropped more. So I put the pressure spring and washers back to where I found it (before oil change with 20w50). I read where the Kelly oil filter has less pleats than a Champion, I believe this would be more restrictive (hince some pressure drop). As far as the pressure fluctuation, it was not as bad. The more expensive gage is steady. I will be watching it closely.

Also I will be inspecting the filter when I change it.
Thanks again,
Ron
 
problem solved

just made a three hr xcrountr and the pressure was steady at 77 psi, 170 deg 2350 rpm, 7500 ft. my mechanic pointed out that the fluctuation was from trapped air in the mechanical gage. I thought is was all out but when I took it out it was there.
 
Glad it seems to be fixed, but make sure you check the inside of your oil cooler hoses when you get the chance. On the flight home right after purchase, the oil dropped to 35 PSI on my Hiperbipe. This was after 2 hours of cruise flight, and directly over the former Castle AFB. Long story short, the suction hose on my Christen inverted system had colapsed (just the liner) and partly blocked the flow. Trouble is, this was a brand new Aeroquip hose that was installed when I bought the airplane to replace a leaking one, so I tore half of the engine apart before looking at a "new" hose.
 
You must log in or register to reply here.