Hot Mooney

[Michael]

My M20C is running hot, Not redline, but close to it. The pressure is normal. This during cruise, not just climb. It is the Lycoming 180HP. I tried adding oil, bringing it up to 6.5 quarts, with no change. The outside temp has been close to 90s in AZ, and 80s in altitude. This hasn't been an issue until the temp has started to rise. when its cold outside, she runs cooler. Wonder if anyone else has had this problem and what did you do?

 

[gkainz]

How long have you had the Mooney? Has it been an AZ plane for a while or did it come from the cold country (like maybe has a winter plate over the oil cooler?) Did it just start doing this and, if so, did anything change?

 

[Michael]

Its been here for years, 15 at least. Havnt done anything new, The last owner said it always ran hot in the summer, I just would rather it didnt run that hot. 350 SMOH. No winter plate that i know of..couldn't imagine it would have one. I know absoulutly nothing about engines. But am going to talk to me mech today. Just wanted to know if anyone else had simmilar experiances.
Thanks

 

[gkainz]

Good luck, Michael. Maybe Eric Jensen will chime in on this - my Mooney experience is pretty limited, with just a handful of hours in a M20J.

 

[Anthony]

Don't M20C's have cowl flaps. Can't you open them a little if the CHT's start to climb above 400F?

Hopefully Len and Eric (the Mooney guys) will see this and comment.

 

[Len Lanetti]

Don't M20C's have cowl flaps. Can't you open them a little if the CHT's start to climb above 400F?

My C has 'em though I've heard that not all of them do.

Note that they are supposed to be rigged so that they are open one inch in cruise. When I originally got my Mooney the cowl flaps were rigged to be completely closed in cruise. Mechanic re adjusted per the maintenance book but prior to that I did not see any temp issues for oil or cylinders.

There are also at least two different cowl enclosure modifications for C models that might affect cooling.

From the original post I thought the issue would be with oil temp's as the post mentioned making sure he was running with a sufficient amount of oil. I've never had an issue with oil temps. On stock C models the oil cooler is right up front on the cowl opposite of the landing light, I think there is an STC to move it to the side with an NACA scoop for cooling air (a second landing light goes where the oil was originally). Possibly, the oil cooler has been moved and/or there are oil cooler issues.

Also, isn't there a thing call a vernatherm that is supposed to control oil flow which occasionally get stuck.

Len

 

[Michael]

My C has 'em though I've heard that not all of them do.

Note that they are supposed to be rigged so that they are open one inch in cruise. When I originally got my Mooney the cowl flaps were rigged to be completely closed in cruise. Mechanic re adjusted per the maintenance book but prior to that I did not see any temp issues for oil or cylinders.

There are also at least two different cowl enclosure modifications for C models that might affect cooling.

From the original post I thought the issue would be with oil temp's as the post mentioned making sure he was running with a sufficient amount of oil. I've never had an issue with oil temps. On stock C models the oil cooler is right up front on the cowl opposite of the landing light, I think there is an STC to move it to the side with an NACA scoop for cooling air (a second landing light goes where the oil was originally). Possibly, the oil cooler has been moved and/or there are oil cooler issues.

Also, isn't there a thing call a vernatherm that is supposed to control oil flow which occasionally get stuck.

Len

Thanks Len. Talked to my Mechanic, and he said the same thing. He is going to check the vernatherm? first. Then flush the oil cooler, and if nessisary he said we can get a larger cooler. But he said he will check to see why it is getting hot first. Been told that alot of mooneys run hot no matter what in the summer time. But, I dont like that answer. Id rather not have to worry about watching the presure gauge the whole flight.
Thanks for your replys.

 

[Ken Ibold]

Been told that alot of mooneys run hot no matter what in the summer time.

Ran my 201 in Florida for years without ever having any kind of temperature issues, even on hot days at max gross where I was trying to eke out all the climb I could.

 

[Henning]

Thanks Len. Talked to my Mechanic, and he said the same thing. He is going to check the vernatherm? first. Then flush the oil cooler, and if nessisary he said we can get a larger cooler. But he said he will check to see why it is getting hot first. Been told that alot of mooneys run hot no matter what in the summer time. But, I dont like that answer. Id rather not have to worry about watching the presure gauge the whole flight.
Thanks for your replys.

Might also want to check the condition of your baffles and seals. Old worn and stiff seals can have a pretty good effect on airflow efficiency.

 

[Len Lanetti]

Thanks Len. Talked to my Mechanic, and he said the same thing. He is going to check the vernatherm? first. Then flush the oil cooler, and if nessisary he said we can get a larger cooler. But he said he will check to see why it is getting hot first. Been told that alot of mooneys run hot no matter what in the summer time. But, I dont like that answer. Id rather not have to worry about watching the presure gauge the whole flight.
Thanks for your replys.

Michael,

What is interesting is that I take it just started running hot, that you had been operating the aircraft under similar circumstances without issue for awhile.

From a troubleshooting perspective I would say, what changed. If you are running it the same as you always have. Either something broke or something wore to the point where it made a difference. I would try to find out what changed and repair or replace as required. I know Grumman aircraft owners often fit a larger oil cooler but when I asked my mechanic about that for the Mooney he said there was no need. He feared introducing other issues and suggested that I simply go with the standard oil cooler.

Actually, from what I can tell the C model Mooney does not run hot by its nature.

I don't live in AZ but I've never seen an overly high temp in the summer here in the Philadelphia area. I also did not have an issue when I brought the plane up from Florida in the summer. I have (had) just the one cylinder that routinly reached 380 CHT before any other cylinder but that was regardless of OAT. This limited the amount of leaning I did (though I guess I could have backed off on the throttle a bit as another option). :<)

Len

 

[Michael]

Michael,

What is interesting is that I take it just started running hot, that you had been operating the aircraft under similar circumstances without issue for awhile.

From a troubleshooting perspective I would say, what changed.

The weather changed. Its in the 90s here now. I bought it when it was still in the 60s. Thats the only thing i can think of.

Michael

 

[Michael]

Steve,
Its runnimg hot durring climb and cruise. And i understand it takes a while for an engine to cool, but mine has been staying hot no matter what altitude, or mixture settings. cruise at over 40 mins, with no change, no change in pressure either, so it wasnt doing any damage...acording to my mechanic. He will check any and all sensors, Thanks for the advise.
Michael

 

[ejensen]

I can keep my F cool but in the summer I have to keep the cowl flaps open except up real high. I also climb at Vy+10 unless there is some reason to max and then I watch the temps. The oil is usually limiting for me. I understand that the air flow through the oil cooler is poor on stock Fs. There is a mod to move to the 201 postion behind the engine. This is suppose to help oil temp alot. I could not climb at Vy long in a Las Vegas summer.

This is on a 300 hour, steel cylinder IO-360 A1A. Cyl Temps on my old chrome engine were higher.

As others have said baffling is critical. Even more with the older 'doghouse' models.

Eric

 

[Len Lanetti]

The weather changed. Its in the 90s here now. I bought it when it was still in the 60s. Thats the only thing i can think of.

Michael

Michael,

Does your M20C have cowl flaps? From what I hear some do and some don't. My 1964 C does have them.

Note that the cowl flaps are supposed to be adjusted so that they are open about 1 inch when the cowl flap control is in the closed position. This is per the maintenance manual. My cowl flaps were initially set to be completely closed when the control was in the closed position. I did not notice any tendancy to overheat during the time period when the cowl flap was rigged this way but then again I don't fly in AZ.

I remember that it took two or three trips to the shop to get the mechanical cowl flap system set up right so that they worked and didn't get blown shut with prop blast.

Len

 

[pete177]

Mooney flaps are not supposed to be 1 inch open when closed, the c model cowl flap is supposed to be 1.1 inch open when fully extended per tech manual.
My '64 E does not use the plastic/silicone baffle material that meets the upper cowl in most airplanes, it's sealed on top by aluminum sheet. These tend to crack. I'd make sure that all holes/cracks in the baffle are sealed with a high temp silicone or other such material as recommended by your a&p. My E would run hot in hot weather in cruise at higher power settings. I would suggest running with the cowl flaps open a bit in hot weather, I think fully open they cost 3 knots in cruise at 10,800ft, pulling 21map/2350rpm.
Also, I've had other mooney owners tell me that the cowl closer mod from www.SWTA.net or Laser will result in a cooler running engine as well as get you a few knots more. They're cheap, about $400.
Pete

My M20C is running hot, Not redline, but close to it. The pressure is normal. This during cruise, not just climb. It is the Lycoming 180HP. I tried adding oil, bringing it up to 6.5 quarts, with no change. The outside temp has been close to 90s in AZ, and 80s in altitude. This hasn't been an issue until the temp has started to rise. when its cold outside, she runs cooler. Wonder if anyone else has had this problem and what did you do?

 

[Len Lanetti]

Mooney flaps are not supposed to be 1 inch open when closed, the c model cowl flap is supposed to be 1.1 inch open when fully extended per tech manual.

Jeez, now I'm going to have to double check the book against what my mechanic told me. At least now is a good time with the thing all apart.

My '64 E does not use the plastic/silicone baffle material that meets the upper cowl in most airplanes, it's sealed on top by aluminum sheet.

My '63 C has the same aluminum sheet.

Also, I've had other mooney owners tell me that the cowl closer mod from www.SWTA.net or Laser will result in a cooler running engine as well as get you a few knots more. They're cheap, about $400.
Pete

I have that cowl closer mod. It is not as neat looking as some of the other cowl upgrades that are available. It was on the plane when I bought it so I have no comparison points for before and after. From what I've heard it does reduce drag and supposidly the cooling was over done originally so adding the cowl does not adversly affect cooling.

Len