Re: Engine runs cold
Its not the heater core if the engine isn't warming up at all. Also, a clogged radiator would be causing overheating, not underheating.
On a cold engine, is the radiator full and the reserve tanker 1/2 full? If not, add coolant.
After the engine has been running and should be hot, are the upper and/or lower radiator hoses hot. Note I said hot, not warm. Also, are the hoses going to the heater core hot, cold, or the same. If they are hot, then you have a gauge/sensor problem and probably a clogged heater core. If they are not hot, then you have something else wrong preventing it from reaching operating temperature.
When the engine is off, can you spin the fan by hand? If not, then your fan clutch is siezed. This will make the fan run full power constantly and I suppose could prevent the engine from warming up if it is cold enough outside.
How old is the water pump? If the impeller is worn out, it won't push coolant with enough force to do its job correctly. This typically causes overheating, but it also prevents coolant from reaching the heater core if everything else is working properly.
Are you sure you got the right thermostat and are you sure you installed it correctly?
Last edited by FireRanger; 01-16-2011 at 10:51 AM.