Hi all,
I have a 2004 TF 160 VVC "Sunstorm". Last week, warm day, I drove in town, slow traffic, lots of speed bumps, and after a while the temperature gauge went up to the 3/4 marker. I turned off the engine, opened the boot and steam came out of the pressure cap on the expansion tank. I didn't hear the fans behind the radiator, nor the one in the engine bay kick in. All in all I lost 1 l of coolant. When the engine had cooled down a bit, I drove home. In a traffic jam the temperature gauge again went slowly up, but with heater and blower on full blast I could get it down again to the normal position (just beneath the 1/2 marker).
I searched the forum and found several tips. I checked the fuses, and they were fine. I removed hood and inspection lid, next the plug from the coolant temperature sensor (for the ECU), a black one, started the engine and both engine fan and and radiator fans immediately kicked in. Engine was cold, car had been standing still for days. I had tinkered two small cable terminals isolated with shrink tubing to fit the two prongs inside the sensor, with short cable ends, and hooked up my multi-meter and watched the Ohms meter with the engine running. (I couldn't get the multi-meter pins to fit the prongs ánd see what I was doing…) On the laptop I had Dieters
table
to check the resistance values. Right after hooking up, engine not running, it read 2.2 kΩ, which corresponded to the outside temperature of about 25 degrees Celsius. After 10 to 15 minutes the Ωs gradually decreased to 170 Ω. The engine at that point was at normal operating temperature (on the temp gauge at least). Both rad fans and engine bay fan were running. I turned off the engine and ignition, removed the multi-meter, hooked up the plug to the ECU, started the engine and both rad fans and engine bay fan remained silent.
According to Dieters table at normal operating temp it should have read 250-300 Ω, instead of 170. This confuses me: if it is a thermistor with Negative Temperature Coefficient, I would have expected the fans to have kicked in earlier instead of not at all when the engine turned hot on my trip through town and in the traffic jam, which they hadn't – although the temp rise in the traffic jam on the way back, could be attributed to the loss of a liter of coolant, I guess. I only topped up the next day, when the engine had cooled down.
Any ideas?
Richard