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Cylinder Head Temperature

backcountry

Well Known Member
During the hot months I have extreme difficulty keeping the cylinder head temperature in the safe range.
No problem on the ground.
Temperature rises quickly climbing after takeoff and hits 230 degrees caution range in only 1000 foot climb. Must level and decrease power. Once I can get to a 70 degree altitude I can cruise at any power I like.
Oil temperature has never been a problem.
The coolant liquid is always at the upper proper level.
 
Post a photo of the inlet opening on your cowl and of the seals around the radiator (reach the camera up inside the cooling duct and take a photo of teh front of the radiator)
 
I couldn’t get anything good with the camera.
But checked the seal from the outside and inside with inspection mirrors. The seal looked good.
Removed bottom cowl and the seal shows it’s been contacting.
However, in the corners it’s possible there maybe air leaking there. RTV had been use but maybe not enough.
I’ve now added enough RTV that should stop any leaks in the corners.
I’ll say some prayers and hope that’s it.
The coolant has always stayed full and the oil temperature has always remain normal.
 
You are using the proper 50/50 mix of coolant, correct?
You've checked the configuration and are sure you have the right sensor selected?

Vic
 
Two good points from Vic....

If you chose to use the Evans coolant for some reason, it will make your coolant and CHT temps run higher.

Wrong sensor configured would cause an incorrect temp displayed as well. If you are using the settings file provided on the Van's Aircraft web site this shouldn't be a factor.

It sounds like your radiator seals are ok.

It might still be useful if you posted a photo of the air inlet of your cowling (looking straight on from the front). Quite a few RV-12's have had the inlet improperly trimmed during the built, which will effect cooling.
 
Just add water . . .

Two good points from Vic....

If you chose to use the Evans coolant for some reason, it will make your coolant and CHT temps run higher.

The reason is - - it (Evans) is propylene glycol, which has lower specific heat, and thermal conductivity than ethylene glycol and a whole lot less than water. It has to balance at a higher temperature to transfer the same BTU's (heat).
 
I've seen one Rv-12 where the front opening to the two radiators hadn't been enlarged as it should have been. His CHT problems went away after he opened it up.
 
The reason is - - it (Evans) is propylene glycol, which has lower specific heat, and thermal conductivity than ethylene glycol and a whole lot less than water. It has to balance at a higher temperature to transfer the same BTU's (heat).

Yes, I know that, but a lot of people don't. They use the Evans straight per the instructions, thinking that it will be a better coolant choice.

It's only benefit is that it has a higher boiling point than standard coolant, but it doesn't cool as well, so the benefits are small and even then, only worth using in very extreme cases.
 
I've seen one Rv-12 where the front opening to the two radiators hadn't been enlarged as it should have been. His CHT problems went away after he opened it up.

Right Tom

That is why I was asking that the OP post a photo of his cowl inlet.
 
Yes, I know that, but a lot of people don't. They use the Evans straight per the instructions, thinking that it will be a better coolant choice.

It's only benefit is that it has a higher boiling point than standard coolant, but it doesn't cool as well, so the benefits are small and even then, only worth using in very extreme cases.

Plus, I think if you get coolant leak, Evans acts as an excellent in-flight paint stripper... :eek:
 
Hope this goes through.
Attached picture of air inlet.
 

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I also removed some DLX-cool coolant and replaced with water. Any little bit of help could do the trick. We’ll see when I fly.
 
Hope this goes through.
Attached picture of air inlet.

Larry, The trimming on your cowl inlet looks good, so that is not a cause.

The next thing I would suggest investigating is your prop pitch.

On initial climb at low altitude immediately after takeoff, what is your engine RPM when climbing at Vy (75 kts)?
 
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