Question about 1998 Chevrolet K1500

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I have an 1998 chev pickup 4x4,5.7L,new 195 thermostat,flushed the heater core (was clean) engine warms to 200 ,when themostat opens it goes down to 150-160 and stays there,then very little heat in cab.

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160 degrees should be plenty warm enough for the heater to work. Did you make sure all the air was out of the cooling system? You can do this by removing the radiator cap, start the engine and let it arm up. make sure the radiator cap is higher than the engine. This will allow the air to escape through the opening. Use a jack to raise the truck if needed. watch the coolant level. When the thermostat opens the coolant level will probably drop. When it does, pour antifreeze in to bring it back up. Each time the level drop, top it off with antifreeze. Keep doing this until it no longer drops and the coolant is flowing good. If the thermostat closes while you are doing this, the coolant will probably spill over the top of the radiator. If it does, wait for the thermostat to open again and top off with more coolant. When you are satisfied all the air is out of the system, put the cap back on and see if the heater is blowing any warmer.

Posted on Jan 02, 2011

  • Jackie Miles
    Jackie Miles Jan 03, 2011

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First you have to make sure there is colant in the radiater to heat up...if full of coolant,try replacing the thermostat....very easy and cheap try...then make sure no air in system after filing,warming up vehicle,and shutting off a few times to work air from system...if there is still no heat and truck is running at temp(Aprox 200 degree) you may have a blocked heater core,and this can be cleaned by backflushing heater core..take both small hoses off of engine and water pump and run a garded hose through it both ways....good luck..Lee

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