My guess it the thermostat is not closing properly. The ECU is "smart"
enough to look at the coolant temperature when the car starts. It then
"knows" that it should warm up after a given amount of time. If the
engine doesn't warm up, the ECU doesn't assume the thermostat is bad, it
assumes the temperature sensor is bad. So the ECU "thinks" it has no
idea what the engine temperature is, so it turns the fan on (and the
check engine light), just in case the engine is hot. The gauge you see
is not really a gauge, it reads exactly in the middle for a wide range
of normal operating temperatures, reading high or low only when the
coolant temperature is extreme.
To change the thermostat, release pressure in the cooling system, lift
up the coolant overflow bottle, disconnect the wire for the sensor and
clamp the hose on the bottom of it with a pair of needle nose vice
grips. This way you will spill almost no coolant. You need a long T40
torx bit to loosen the thermostat housing bolts.
--
Mike F.
Thornhill (near Toronto), Ont.
NOTE: new address!!
Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
