High CHT on O-540

deroque

I just purchased a 1979 Piper Dakota. I just had the engine overhauled and have about 30 hours on a overhauled O-540. The CHT on Cylinder #2 and #3 exceed 425 degrees on climb out but settle in at 400 - 410 degrees. All other cylinders are fine. In the Lycoming O-540 manual it says that 435 degrees on high cruise is not to be exceeded. Talking with several A&P's they all express concern about the high CHT's. I have had the baffling completely redone as well as the timing checked. Any ideas why my CHT's might be high or is this normal for the O-540?

Scott Sherer

First, determine whether it's the sensor or the cylinder. Have them swap sensors with those from other, good, cylinders and see if the temps are the same. If so, you have a real problem needing attention. If the high temps move with the movement of the sensors, then you have bad sensors. Start there, then let's discuss baffling. I've forgotten, do you have cowl flaps?

deroque

Thanks for the comment. There are no cowl flaps. I will have them swap the sensors to see if that is the problem. I also just had the baffling checked and all spaces were sealed. The baffling seal with the cowling was checked and is also very good.

Scott Sherer

Ok, good luck and circle back here when you have time. Thanks for the update.