Mooney M20E 1975 CHT high but oil temp low

[ighazali]

Have not had any issue but have a concern with the cht being high. When in cruise flight they cool down and in a cruise climb at 120mph they are running at the edge of the green arch. Also in ground operation with cowl flaps open CHT rises pretty rapidly not to exceed the red line. Attached is a picture of the engine temps and instrumentation, picture was taken during a steep turn maneuver, but have been seeing the same indications up until reaching cruise flight and then closing cowl flaps after seeing cht decreasing. Not sure if it may be faulty due to oil temp running cool. Engine only has 50 hours SMOH. 

[47U]

9 hours ago, ighazali said:

When in cruise flight they cool down and in a cruise climb at 120mph they are running at the edge of the green arch. Also in ground operation with cowl flaps open CHT rises pretty rapidly not to exceed the red line.

Welcome… pretty E model you’ve got there.

I’m a C owner, O-360, but my CHT doesn’t act that differently than yours.  Of course, I have a doghouse, which presumably your ‘75 E doesn’t have.  And you have an ARI or SWTA cowling mod?  I’m not sure what affect that has on CHTs.  At only 50 hrs SMOH you could still be breaking in the cylinders, especially if the overhaul shop didn’t run it on the test cell.  Was the overall done with chrome  cylinders?  They might have a reputation for running hotter CHTs.  

So, start with standard troubleshooting the baffling.  Good sealing against the cowling, the flexible pieces are bent the correct direction, gaps around the starter and alternator, inter-cylinder baffles on bottom of the cylinders are installed correctly.  There’s many threads on lowering CHTs.

As far as low oil temperature, I’d start with verifying the gauge is accurate.  The sender can be put in boiling water to verify.  It that’s good, then looking at the vernatherm to make sure it’s opening and closing properly.  There’s threads on that, too.   

An engine monitor is a good thing… my factory CHT runs hotter on the scale than what is indicated on my UBG-16.

Top picture is from the sales ad showing the gauge scales more clearly…

[Shadrach]

Very good advice above.  I fly an F which should have the same engine and cowling combo as your E, save for the cowl enclosure which I do not have. The only thing I can add to the comment above is that if indeed your CHTs are running in the mid to high 400s in cruise, that is much hotter than any angle valve Lycoming I've ever operated. In my experience, angle valve IO360s usually run considerably cooler than parallel valve O-360s.  My IO360 runs low 300s in the Midatlantic summertime temps. In winter, #1 and #4 ure usually in the high 200s. Excursions to 400 are rare and would require hot OATs, low IAS, high deck angle and high power.  It would require an extended period of inattention for any of my CHTs to exceed 375.

Verify the instrument's accuracy before you anything.