Why does my 87 22r get progressively hot while idling?

 

Does it get hot ONLY while idling and (I assume) sitting still?

If so, check your fan clutch or electric fan. It may not be engaging and pulling air through your radiator when at idle/slow speeds. Once you get moving, your speed is pushing more air through the radiator than the fan could anyway, so you wouldn't notice a fan problem then.

 

How do i kno if its not working properly? Could it be my sensor because the temp reads super low at times?