Rear Engine Oil Temp

[Paul Sharp]

Over the weekend when climbing to 17,500 for cloud clearance, noted that the rear engine oil temp reached redline. So pulled that engine back and increased the fuel flow some, opened the cowl flap - all in an attempt to get the oil temp back down. The oil pressure and cylinder temps were all normal. The cylinder temps went down to the bottom of the green but the oil temp stayed up there.

Finally, when over the mountaints (about half an hour, shut down the rear engine as a precautionary measure and went another 20 minutes to KIDA where I landed. On the ground I removed the avionics access hatch and swapped the oil temp gauge wires. Before swapping the rear was still reading at redline even though the engine had been shut down for half an hour including some 20 minutes in flight. Then after swapping the leads, the one being fed from the rear sensor was reading about normal operating temp on the front gauge. The one feeding from the front sensor (now on the rear gauge) read low, about where one would expect it to be by that point in the engine's cooling cycle.

So I left them that way and flew on home to KSLC. Both read aproximately normal during the ifnal hour's flight.

I don't know if those things are calibrated so that if you switch them around like I did you don't get good readings, but I know at least that the rear sensor was "stuck" in a high setting. So I'll replace that one.

Meanwhile, might I have cooling problems? I've read things in the past about rear cooling, and this is the first time I've had any trouble with it (assuming the sensor wasn't just going bad which is always a possibility). I know to have the mechanics check the oil cooler and fittings to it, etc. What else is there to check?

Is replacing the sensor difficult? Are they very expensive?