I'm having a similiar problem . My car will go over 1/2 temp on the freeway after you are driving it a while. It will also do this around town after a while. If you have the AC on the AC will get warm, then the car temp will go up then under 1/2 and the AC will get cool again.

It can be stable with normal temp for a while, then it will go up.

So far I flushed the coolant, got a new cap, checked to see if the fans were coming on(both go on when the AC is on).I'm gonna try bleeding the system. Tried an aftermarket thermostat and its still gets hot.


I don't have any water in the oil/oil in the water or white smoke.

I'm starting to wonder if the AC clutch is slipping, which causes the pressure to build in the condenser and the heat
Could the AC clutch slip which causes the AC to get warm which somehow ads heat to the radiator?

I did the timing belt/bent vavle last year and it ran fine all Summer. I hope it isn't a head gasket or cracked head....