I have an '89 240 wagon that recently began having a temperature problem. On starting, the temp gauge slowly rises (as usual) as the engine warms up, but lately the temperature continues to rise into the red zone, at which point I shut the car off to cool things down (don't want to drive in that condition).

A few years ago I had an erratic temp gauge which I fixed by replacing the temperature compensation board, but that time the temp gauge was jumping around. This time it rises and at highway speeds it will slowly fluctuate between "red" hot and normal but not necessarily tracking up or down with my speed.

In the last year, I have replaced the water pump, thermostat (at the onset of this problem, but didn't affect the temperature problem), and radiator. We had some snow last week and I had the 240 parked. I started it up after a week of being idle and it cranked up fine, and after a few minutes the temperature rose again. However, this time I also noticed the engine idle would jump around. Every couple of seconds the rpms would rise, then immediately fall, rise, then fall. If I give it some gas the engine sounds fine, purrs like usual.

So, what's my problem? I haven't gone for another temp compensation board yet since the gauge isn't "jumpy", but I'd go for it if that would solve the problem. I've been driving my 740 lately until I get this figured out. I've even considered selling (gasp) the 240 to reduce the cars in the driveway; I'm up to 4 now: 240, 740, V70, and F150.