I had the same problem last winter. When it is really cold out, it will only warm up idling. If I'm moving at a steady pace down a road with no lights it won't get any warmer then 130 F. Is this normal? Is there any way to fix this other then cardboard over the rad?

On the other hand in the summer, I had the opposite problem, where if it were moderatly hot out it would climb fast at a light...it went back down as soon as I turned the rad fan on, but still...

I installed a drilled ZZP 180 thero during the summer. It has made no difference...

Thanks

I know its a stupid question but, have you checked your coolant level and is it the correct mixture?

Yeah...coolant is full...I have no reason to beleive it isn't the correct mixture. Anyone think a flush may be in line?

Have you checked to see if the fluid is moving? My first thought was a bad thermostate, but you said you replaced it. It could be a bad waterpump or blocked waterjacket.

You may have air in the system. Tech article on this.