I have a 2000 Toyota Tacoma TRD. Recently I noticed that my heater wasn't blowing out hot air. It is luck warm, and in Pittsburgh it is now in the 20's. When I run my truck my upper hose is hot and my lower hose is cold. Does that mean my thermostat is broke? Or could it be something else?
The upper hose is supposed to be hot. That's the hot coolant from the heads going through the radiator for cooling. The lower hose is supposed to be cool. That's the cool coolant going to the engine. The thermostat diverts just enough coolant through the radiator to hold a constant coolant temperature in the heads, and in the winter that won't be much. If your temperature gauge is rising from cold to normal at the usual rate, and it holds at the normal point on the gauge as it should, your t'stat is OK.
Your warm heater could be a couple of problems. Check that the hot coolant valve is really opening all the way. Check that the coolant level is OK. Check that the air passages are clear. Have someone show you how to disconnect the air conditioning when you're using defrost. Unlikely that you have a clogged heater core on a 2000.
Ken
Bubble of air in the system? My 1975 Honda engine had a small release valve at the highest point of the cooling system for the sole purpose of purging air in the system.
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