Hi all, I have 1990 dlx with a 22re. I think there’s a water circulation problem. The truck has always run well at temp, and a few days ago I noticed the temp climbing quickly past mid gauge when the truck was at a stop after driving for a few minutes. From a stop, with acceleration (at least 30-40mph) and then maintaining speed the truck temp will skyrocket and then cool off to normal
and stay there. At a stop I can sometimes get the temp gauge to move (Reving the engine in neutral, the gauge needle moves some).

I replaced the thermostat (180 not the two stage) and that seemed to help for a trip or two, now back to ground zero. I can not locate a drip under the pump. I have had to put in at least a quart or two of coolant, so I think it’s losing it somewhere. The radiator is newish. I can’t tell how much play is appropriate in the fan. I did also replace the alternator a few months ago so maybe there could be belt tension problems? There is some belt noise on startup and maybe when the pump is trying to start up again at speed.

Is it the water pump? What else can I check to be sure?

 

First find your coolant leak, do a pressure test and see where it is going, either on the ground or into the intake or into the cylinders or into the oil pan.

 

If it's losing coolant, you should be able to see and smell it if something is leaking. Otherwise, it's going into the oil, or out the tail pipe.

When mine was using coolant, it was going out the tail pipe, but it was not running hot. Had to install a new head gasket.