Sounds like a bad thermostat or thermostat in backwards.

dcollivier wrote:
> 90 Cherokee 4.0L back on road after winter, it now overheats. I changed
> the thermostat and refilled. Still overheats. I thought that maybe it
> could be an air lock or something, but after playing with the system I can't
> seem to get it any better. I tried burping the system by cracking the hoses
> open one at a time and allowing some air out but it did not seem to help.
> It does not seem like there is any flow in the upper hose at all, but there
> is coolant in it. Any other check for a waterpump before I throw parts at
> it. There is no leaking fluid anywhere in the system, the shaft on the pump
> also feels fine. Any help would be appreciated. Dave.
>
>