in the morning when im driving my 4 cyl. truck, if the heater knob is turned to the heat side ( does not matter if heater is turned on or not) the temp gage goes to a little over 1/2 way and then starts to go down to normal ( about 1/4 to 1/3 ). only does it after a cold start, once motor is warm dont have any issues. heres the weird thing. if i have the knob turned to the cold side in the morning it does not go over 1/4 on temp. seems to run cooler if i have knob turned to cold position. already changed thermo stat. what could it be? thanx.
93 toyota truck heating question
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On the 22r the heater core return dumps near the thermostat. This water has been cooled by the heater core and is just cold enough to close the thermostat. Once the engine is hot the water usually wont allow the thermostat to close all the way. Toyota has a dual diaphragm thermostat if it really matters to you. The smaller of the two wont close with the heater on and keeps hot water flowing past the main thermo valve for smoother temperature control.
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I'd just drill a hole or two near the edge of the thermostat. This lets just enough water pass through to let the thermostat know the true temp of the engine, and allows it to stay open. If you drill too big you could have some warmup issues but a pair of 1/8" holes should do the trick nicely.
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