High Cylinder Head Temp

[Mooney-Mark]

Departed NYC metro area at gross weight last week. OAT was about 90 and hit red-line cylinder head temp in climb to 8,500 for about 10 min. Wondering what type of engine issues may arise.

[Hector]

Do you know the exact temperature? And do you mean to say the climb was 10 minutes or were you red line for 10 minutes (hopefully not the latter)


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[kortopates]

very brief post doesn't give us much to go on, but if you have an engine monitor the first thing would be to download the data and confirm what happened and for how long. But if you truly exceeded lycoming redline of 500F I'd be borescoping the cylinder(s) before further flight as well as looking for signs of any cylinder cracks or other excessive heat damage.

[Oscar Avalle]

Yes, be very careful and get a engine analyzer. My CHTs are on the higher side and I use my JPI to manage the temps to keep them below 450 in climb....

oscar

[Jim Peace]

22 hours ago, Mooney-Mark said:

Departed NYC metro area at gross weight last week. OAT was about 90 and hit red-line cylinder head temp in climb to 8,500 for about 10 min. Wondering what type of engine issues may arise.

without an accurate engine analyzer you really have no idea what the temps were....or the RPM or anything else......

[Brian Scranton]

Yeah dude...need more info. I could be everything from a slightly bent baffle to a mini dragon.

 

[carusoam]

Welcome aboard, MM.

Realistically, An M20C with a single CHT... has a redline at an unbelievably high value...

This is good from an engine safety point of view....

But absolutely silly from a cylinder owner point of view...

Most people around here want to keep their CHTs under 380°F when able... for economic reasons... they wear less...

Another thing that happens with really hot cylinders is oil tends to coke (degrade into carbon) in the hottest part of the cylinder... exhaust valves and their guides get much hotter as the CHTs are run hot... as the oil cokes in the valve guides, the lubrication decreases... leading to sticky valves... there is a procedure for cleaning the valve guides...

To minimize the CHTs... cowl flaps open, cruise climb at 120ias... Keep an eye on the CHTs. 

adjust mixture 200-300°F ROP during the climb...

It would cost less to run deep ROP, and get a decent engine monitor, than to wear out a set of cylinders...

OK, I made some assumptions...

I flew my M20C by the 1977POH and only had a single CHT gauge... and No MS...

You want to get a few things...

• A 1977POH for the M20C
• An engine monitor that can download data
• A strong desire to read a lot of MS 

Expect that cylinder wall wear is going to increase the longer you fly near red line... to see how much cylinder wear you currently have... people send dental cameras down the spark plug hole to get a look AT the crosshatched surface of the cylinders... if the cross hatching is missing near the top... that is a sign of a lot of wear...

Other signs of wear... the smell of exhaust in the oil... the oil is really dark after a few hours of running... oil is missing after a few hours... oil is foamy after flying... exhaust is getting past the rings... that kind of thing...

PP thoughts of a PP, not a mechanic...

Best regards,

-a-

[Mooney-Mark]

Thanks everyone for the advice.  Did not exceed red line but CHT was up to red line for a few minutes. I think that a trip to my mechanic may be in order. Also looking at installation of a JPI EDM 800.

Mark

[Aviationinfo]

For next time, don’t forget that you’re not without options in such a situation.  Enrichen the mixture, stop the climb and accelerate until it cools, reduce power, etc etc.  You may need to climb in steps.   

If you’re just looking at the basic old Mooney cluster gage CHT then you really don’t know what temp it’s showing you—it’s just as likely to be out of calibration as it is to be correct.  If the actual temp probe happens to be of the spark plug gasket type, those tend to read high vs bayonet probes.   

[ArtVandelay]

If the actual temp probe happens to be of the spark plug gasket type, those tend to read high vs bayonet probes.   

Gasket probes read LOWER or cooler than bayonet probes because they are measuring surface temperature, about 30-40° less in my experience.

[Aviationinfo]

40 minutes ago, teejayevans said:

Gasket probes read LOWER or cooler than bayonet probes because they are measuring surface temperature, about 30-40° less in my experience.

Wow, ok.  Yours is the first case I’ve read about.  Your explanation makes complete sense but in my own experience and when discussed on other forums, the gasket probes read higher than bayonet.   I have no idea why. 

[ArtVandelay]

First is with 830 and gasket probe on cylinder 3:

Second is with 900 and bayonet probe:


#2 gets tons of air, so that’s why it runs cooler.

[Tommy]

It depends on where you put the gasket probe. If you put it on the top spark, it reads lower, if you put it at the bottom it reads higher.

[carusoam]

+1 for getting a real engine monitor...

There is so much real, useable info available for an old bird...

Single CHT and single EGT is just barely enough...

Most important challenges we get.... are single cylinder issues.  Hard to see without a monitor.

If extra cost conscious there are used ones available that are pretty good...

Add FF and carb temp if you don’t have them already....

Best regards,

-a-

[Mooney-Mark]

Thanks carusoam.

[kortopates]

It depends on where you put the gasket probe. If you put it on the top spark, it reads lower, if you put it at the bottom it reads higher.

It definitely goes both ways, higher or lower. But I don’t think we can say conclusively one way or the other depending if top or bottom. The moral is the same though, we can't rely on gasket/washer CHT sensors. Anyone stuck with an advisory installation is much better off installing an adapter sensor that piggybacks off the OEM sensor - they are much more accurate and the best you can do till going to TSO'd primary monitor.


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