High Oil Temps and Baffling

[TerryDubYa]

Fellow Mooney Nuts,

With temps back up into the 90's, I keep running up to redline on my oil temps, requiring a lot of enriching and leveling off to keep them in line.  I've looked at the baffling previously and it appeared to be sealing well.  I took a closer look today and noticed a big gap at the front of the cowling under the flywheel/starter/alternator area.  Ram air was deleted previously.  Should there be baffling in this area?  Is that gap necessary for something like providing airflow to the muffler?  I'd appreciate any observations!

Terry

M20J@KLBB

[carqwik]

Check the vernatherm.  Perhaps oil is not going through the oil cooler?  Not an A&P...just a hunch on my part.

[Oldguy]

I assume you have also done the flashlight/trouble light in the back of the cowling when all buttoned up, and no big light leakage spots when looking through the air inlets in front? With the bottom cowling on, you should be able to look down at the (former) ram air intake and see if it is sealing below it. It might be leaking there, but if these oil temperature problems are relatively new, and the ram air was not recently removed, I would vote vernatherm as well.

Nice to see my older sibling is still around. 

N5767Z 

24-1492

[jaylw314]

Yeah, the M20J does pretty good on keeping things cool, so oil near redline is not typical.  If anything, I have trouble keeping the oil warm enough.  It's hard to imagine the gaps at the front end would cause enough pressure loss up top to steal pressure from the oil cooler.

If it was a cooling issue, wouldn't your CHT's be high too (especially #4)?

[TerryDubYa]

Thank you, gents.  No issues with CHTs, so sounding like the vernatherm.  Oldguy, mine is older by a week maybe...24-1491.

[carqwik]

Btw, are you sure there's not a problem with the probe or the gauge? 

[jaylw314]

9 minutes ago, carqwik said:

Btw, are you sure there's not a problem with the probe or the gauge? 

How does one check the sensor, other than swapping it out for a new one?

[bonal]

4 minutes ago, jaylw314 said:

How does one check the sensor, other than swapping it out for a new one?

Checking the sensor and gauge is easy just remove sensor have a calibrated thermometer a small vessel for oil or water a heat source capable of reaching boil and heat liquid with thermometer and sensor and compare temps. We were having high oil temps nearly redline. After replacing vernatherm we saw a reduction of about 15 to as much as 25 degrees on our oil temps. When you inspect the vernatherm look for wear on the plunger as it may be operational but not making a good seal against the engine case. Remember a vernatherm works opposite to the way a thermostat in a car does.

[jaylw314]

45 minutes ago, bonal said:

Checking the sensor and gauge is easy just remove sensor have a calibrated thermometer a small vessel for oil or water a heat source capable of reaching boil and heat liquid with thermometer and sensor and compare temps. We were having high oil temps nearly redline. After replacing vernatherm we saw a reduction of about 15 to as much as 25 degrees on our oil temps. When you inspect the vernatherm look for wear on the plunger as it may be operational but not making a good seal against the engine case. Remember a vernatherm works opposite to the way a thermostat in a car does.

That seems obvious now that you explained it.  Duh!

[Guest]

While likely un related to your oil temp issue There is no reason to leave that large gap where the ram air door was.  Add some new baffle seals, you might also want to use some silicone to seal around the starter motor and an additional piece of baffle seal around the alternator.

Clarence

[Piloto]

A one inch gap at the cowl flaps trailing edge will drop the temps by 50F or more. Just adjust the flaps turnbuckles. No effect on speed performance.

José