Help required! Any Lycoming guru's about?

[Grandslam]

Headscratching...!

I have a 6 pot Lycoming fitted to a Pawnee. It is a new engine fitted 2 weeks ago, the run in flights have been completed iaw the flight test papers.

However, the engine suffers from high oil temp, with no great loss in pressure. The previous engine was also running a little high.

Has anyone else suffered the same problems and have a cure, failing that does anyone have any ideas?

Many thanks.:8

[stevef]

IO540. First thing I'd check is the gauge, seeing as the temp was high with the previous engine. Next I'd look at the oil cooler. It should have been cleaned of bits of grass and dead bugs on the engine change though, as well as being flushed.

[SNS3Guppy]

If your oil temp is running hot, determining if the temp is reading correctly is a good start. Checking calibration against a known temperature source (running the oil temp probe in water at a known temperature, for example) is a way to establish if the probe or indicator is at fault.

If indeed the oil is hot, assuming quantity is good and pressure isn't an issue (insufficient flow), then you may have a bad vernitherm (thermostat), a stuck oil bypass, a blocked cooler, improperly configured baffling, etc.

If the engine is running hot, you should be seeing it on other indications, such as high EGT's and CHT's if you have plugged injectors, misfiring plugs, induction leaks, etc. A word of caution, however...you may have the problem and see no indication depending on the type of instrumentation you're using (single point EGT, for example, doesn't tell you more than what one cylinder is doing).

We had high engine temps in a pawnee we ran, and one solution employed was the use of glass wraps on the exhaust. This isn't an option on a certified aircraft doing most types of flying, but it was doing ag work, and it worked very well. By employing exhaust insulation similiar to what might be found on drag racers, the heat went out the exhaust and not in the cowl. Engine temps and oil temps dropped substantially.

That shouldn't be necessary for you, however. Check that you're not by passing the cooler, and that your calibration is correct.

What type of flying are you doing with the pawnee? If you're doing towing such as gliders or banner work, you may need to run slightly richer on the mixture, slightly higher on the airspeed,and accept reduced climb rates, to promote better cooling. Have you verified proper cooling and airflow at the oil cooler?

[hung start]

when you get it sorted out , run with a lower quantity oil ( still on the dip stick ), this will lower your oil temp aswell . The oil goes through the cooler quicker and dosent sit in the sump and get hot . I did this with a c208 ( parachute flying )and dropped the oil temp by 15 degrees ,and pawnees .As long as the oil is on the dip stick you shouldnt have any problems

[etesting2000]

Couple Questions.

The original engine ran warm. Are ALL the required baffles in place?
Not what it came with, what it was manufactured with.

Then as said above verify instrumentation and oil cooler.

[Grandslam]

After replacing/testing several components it appears that the Vernatherm was U/S on fit.

A/c is now up and running.

Thanks for all your suggestions/help all.

[stevef]

Thanks for the feedback, Grandslam. Some people don't bother to return to the post after requesting assistance, which as well as being impolite, doesn't make the solution available to others who might encounter a similar problem in the future.
Glad you're back in the air.