1996 Silverado Has no Heat or Coolant Flow

1996 Chevy truck. Vortec v6 4.3L.
Question Here: What possible issues could be preventing coolant from flow through the heater hoses? The water pump, thermostat and heater core all appear to be working properly. The water pump circulates the coolant once the engine reaches operating temp. 185-190d. The thermostat appears to be opening as needed... truck doesn't run hot (when the temp appears to be on the rise above 190 it will soon go back down). I can flush water in either direction through the heater core. The coolant level is full. I have also purge the heater core of air. Both hoses NEVER get hot. Pull either hose or both while the engine is running and there is no flow. ANY HELP?

Answer: I assume you are having a problem of no heat in the truck. Sounds like the thermostat and water are functioning properly as you stated. As long as the temperature does  not go down TOO low after reaching 190 degrees. If there is no flow through either heater core hose, then there is a restriction somewhere. One hose comes from the fitting in the passenger side on the intake manifold. The other from the top of the water pump. Check those for restrictions. That may be deteriorated internally preventing flow. If the thermostat or any other cooling system component has been replaced prior to this condition, and they used silicone on the gasket- or silicone only, that has a tendency of getting into all sorts of places and causing a restriction.

Chevy Silverado Overheats

I have a 1994 Silverado side step. When I first start up in the morning and drive, truck runs hot after about 3 miles and stay there for about 1 mile and then drops back down to normal operation temp. After sitting and cooling down it will do the same thing again. The thermostat has been changed three times and the cooling temp sensor has been changed also. What could possibly cause this?

Answer: My first thought was a sticking thermostat, but obviously that is not the case. Overheating then correcting itself is very weird. It almost sounds like there is a restriction. I would check for a restricted internal radiator. Use a laser thermometer on several spots on the radiator to see if there is a cold spot with a hot engine. A cold spot on the radiator means no coolant is running through that are.

Also see if there are air bubbles in the radiator when the engine is running. If there are, then this is a sign of a blown head gasket pumping compression into the cooling system causing air pockets.

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Comments (2)
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  • Guest - troy

    I have a 2005 Chevrolet Impala and I went down south for a few days and while I was down the there, the heater was not working. The vents were working properly, but it just would not heat up. It just blew cold air. What could the problem be?

  • Guest - Tech

    In reply to: Guest - troy

    I'm going to assume the car still reached operating temperature and just didn't blow hot air out the vents. There is a temperature door actuator that is probably bad. If you have dual zone climate control, check to make sure both sides are acting the same way. You may have heat coming out the passenger side and not the driver side, or vice versa. If that is the case, then the actuator would need to be replaced for whatever side isn't blowing hot. If you've got dual zone control and neither side blows hot, you could have a control head problem, an electrical issue, or more.