I was driving, pulled over to get a text message and all heat from vents turned cold, engine temp raised above normal, all corrected when I drove again. This symptom happen about 2 weeks ago, at that time, I replaced the thermostat, and the symptom went away, also the truck has a random miss, according to Autozone plug in thing, the miss is bad from 0 to 25 mph then only slightly noticed at higher speeds. Also I just replaced the oil cooling lines recently. '99 s10 w/ 4.3 Vortec V6, 4x4 ext cab
Mostly looking like a thermostat problem. Stuck closed with no liquid coolant circulation. When a thermostat stuck open the coolant flow well and dont give the chance to coolant to become hot so no overheat and no heat for heather. When its stuck closed no coolant going to the heather core so no heat inside the truck but all heat staying inside the engine. Thermostat maybe faulty again or the water pump going out of life.
December, 31, 2011 AT 7:42 PM
Check to make sure your heater hoses are both hot. If they are, then check the actuators on teh heater unit to see if they are working. One is for air direction the other for heat/cool. If they are vacuum look for a vacuum line off or a leak as that can cause your problem. I'm sending a generic pic along, they are under the dash.