I have a TB-10 with O-360. I have the original single-cylinder gauge only, and it consistently reads 500 shortly after takeoff. I am quite aggressive in my attempts to manage temp, and I see no other signs of trouble. I’m wondering if there’s an issue with the gauge, because even in cruise it never goes below about 425. I plan to install a GI-275 EIS later this year, but in hundreds of hours flying behind O-360s in other airplanes (without CHT gauges) I never even gave this any thought—and I wouldn’t if I didn’t have the gauge.
I should say that I am sure I’ve been flying it this way for the last year and a half, and only noticed a few months ago because I never had a CHT gauge before. I looked back at a couple old in cockpit videos from last year, and sure enough the gauge was up at 500. There are no other symptoms, no metal in the oil or engine roughness—nothing that would indicate any trouble if I didn’t see that high reading. It seems like I would be experiencing serious trouble if the reading is correct, but it still makes me nervous. Any other reasonable explanation?
500 is Lyco redline. According to Busch, Deakin and others, the 500f limit is an emergency limit severely restricting engine life (metal strength degrades significantly over 400f). To ensure longevity, limit CHT to around 380f on standard temperature days. On hot days a bit more, on cold days a bit less.
I wouldn’t be too concerned for now, watch out for change to your usual temperature patterns though.
Some possibilities:
*CHT gauge is over reading or generally just inaccurate. Where is the probe located?
*Baffles need improvement
*Climb shallower and see if it reduces CHT/Oil temp
Without a 4 cylinder engine monitor it’s difficult to troubleshoot.
I’d say have the gauge and sensor bench tested.
If it is that high, there is something wrong with the cooling of that engine or rather with the baffles. I fly the same O360 in the Mooney, which has notoriously bad cooling, but have never seen more than about 425 F.
Definitely worth getting the gauge checked. Even the last days with OAT in high 30’s we were not hitting our “redline” on any cylinder which we have set on the EDM as 420f
Search “Tempil”. They have a number of products which indicate a maximum temperature reached on a surface to which they have been applied. They are inexpensive, and accurate. Select the temperature range/threshold you’d like to capture. Apply them to the surface you suspect, and go flying. Take notes on the maximum temperature you saw indicated, and check the Tempil after you land.You’ll know where to go from there.
500F is rather hot for CHT, so I’d be assuring that the engine is not actually experiencing that.
500F is way too high. You may need to fix your baffle seals.
