Oil pressure follows throttle

jerryab · #1 10-01-2009, 11:05 AM

Recently while flying back from Texas, I noticed my oil pressure was past the redline and the oil temp was climbing close to the redline of 245 degrees. I made a precautionary landing. Now no one seems to know why this happened!! The is an 0320 with 250 hours since factory new. The IA said the oil presure followed the throttle to 110 lbs and it shouldn't do that past 70to 80 lbs of pressure. First, he removed the "varatherm", which was no small job. It checked fine. Never found any reason for the sudden high oil pressure or temp, so he is turning down the oil pressure regulator so it now will read 45 lbs at idle as the solution. He did hook an external pressure guage to the rear of the engine to verify my guage. The filter was cut and nothing was found. Can anyone think of anything this might be? Just turning down the regulator to me doesn't fix anything. Of course it had plenty of oil.

n721dp · #2 10-01-2009, 11:11 AM

Hi,
Whose gages do you have? I'm betting Van's electric.

If so, it's probably expected indications with a bad ground or corrosion on some of the wire terminations.

N941WR · #3 10-01-2009, 11:14 AM

I would verify the gauge and probe are accurate before turning the varatherm down.

jerryab · #4 10-01-2009, 11:20 AM

We have verified the oil pressure guage by using an independent guage. the Veritherm was removed and tested for operation. I appreciate your input.
Jerry
RV6A

pierre smith · #5 10-01-2009, 12:32 PM

....these oil coolers can congeal in very low temps.

It happened to me several times in Cessna Agtrucks....same symptoms you describe, so we simply landed as soon as possible and waited a bit....15-30 minutes while the engine heat softened the congealed oil in the cooler and we were good to go.

Possible?

Radomir · #6 10-01-2009, 12:53 PM

One unfortunate possibility is a lost [rod] bearing.. You should check the finger strainer in the sump for large metal shavings.. so large that they wouldn't even make it into your oil filter..

You mentioned red lining the oil temp... that oil got hot all of the sudden for a reason... and typically it's not something you'd like to hear

647jc · #7 10-01-2009, 02:45 PM

Both high oil temp and pressure sounds like a plugged oil system to me. Pierre's explaination of a plugged cooler sounds most plausible to me.

pierre smith · #8 10-01-2009, 02:56 PM

...a little more. It congealed on a cold, Winter day shortly after leaving the Cessna Delivery Center in Wichita....temps in the 30's and it didn't take long to climb after takeoff. You essentially have no cooler in line when that happens and the block mounted oil coolers on the IO-520's were rather prone to congealing with 50 weight oil. We didn't have multi-viscosity oil in 1972 IIRC. As I said, a little while on the ground took care of that. Later, they developed non-congealing oil coolers and the problem was gone.

In my RV, sometimes my CHT gauge goes over to the peg but I've learned to ignore it until I have a chance to jiggle the probe at home, then it works for another 6 months to a year and starts this again...sigh..could be a probe or sensor or temp sender in your case with an erroneous reading as a result.

Regards,

jerryab · #9 10-01-2009, 09:23 PM

I will post what is eventually found, I'm very suspect of the oil cooler at this point, nothing was in the screen. going to test fly it tomorrow!! A very big thank you for all of your input, that's why I love this forum. Worth every dollar of my contribution and much more.

DanH · #10 10-02-2009, 09:53 AM

Quote:

Originally Posted by jerryab

I will post what is eventually found, I'm very suspect of the oil cooler at this point, nothing was in the screen. going to test fly it tomorrow!! A very big thank you for all of your input, that's why I love this forum. Worth every dollar of my contribution and much more.

Jerry, there is an accessory case oil system schematic and some filter adapter information here:

http://www.vansairforce.com/communit...ad.php?t=45548

Consider your problem and do a little "corn maze tracing".

An oil cooler blockage will raise temperature. It will not raise pressure as measured at the usual pressure port location, which is downstream of the entire cooler/filter/vernatherm section. A blockage of anything in that section will reduce indicated pressure.

To raise pressure you must either block flow through the oil pressure relief ball valve, the ball valve's drain port to the sump, or to some significant portion of the engine oil gallery tree.

I would remove the entire oil pressure relief valve assembly for inspection of the valve and sump port. Run a soft wire down the port.

If nothing is found I would connect a mechanical pressure gauge to the left main oil gallery (you've already measured pressure in the right gallery). As I recall internal oil distribution, the left gallery is fed via flow across a bearing shell or shells. (Somebody check me....the front cam bearing on a 320?) Low left gallery pressure can indicate a failing bearing; the debris blocks the passage.