99 gmc somoma overheats at slow speeds

Question

The water pump was replaced last year I just changed out the thermostat hoping that would fix it. It still over heats when running the AC at slow speeds and stoped at a light. the clutch fan does not spin freely but I im not sure what ells could it be. Should I just try to replace the fan or take it in to get fixed. My skills are limited I replaced the water pump so im sure the fan should not be to challenging I just had a problem with those 4 bolts on the fan when putting the pump back on

Answer 1

check to make sure the rad is clear of debri, may have to blow it out, along with the a/c condenser, the clutch fan should have a little drag on it until it turns for a minute, by hand that is, and not with the engine running, it sounds like your not getting enough air flow through the rad at low speed. also, is the fan shroud intact ??, if it's missing in part or whole the air may be drawn from around the rad by the fan, and not through it.

Answer 2

Overheating at slow speeds and idle usually indicates inadequate air flow over the radiator.  My first instinct would be failed fan clutch allowing excessive slip.  If your sonoma came with a HD clutch it will be controlled by an internal thermostat with a failure it will not increase resistance during higher temps.  I would closesly examine the clutch and if you haven't flushed the radiator recently flush and fill.  I suspect that will remedy your problem.  Hope this helps.