Hey all,
Have a 2000 XKR with 45k miles. The previous owner had the cooling fans, thermostat and water pump replaced by the dealer. Now the cooling fan (only one) is running too long.

At first I never noticed the fan(s), then they gradually increased the time they were on and when they started being on for 90 seconds or so I had the cooling system flushed and refilled. Now (a few days after the flush) the fan runs for 4-5 minutes. I read the forums and realized I should have had the thermostat replaced at the time of the refill. That is next on my hit list.

My mechanic advised me however that the only fix is to replace the fan assembly, and he didn't even mention the possibility that it could be the thermostat. I wanted to know what drove the fans to be on, and he said the reason to replace the fan assembly is that the sensor that drives the fans is built into the fan assembly.

I read in one forums that the fans are driven by the ECT sensor.

What does the ECT sensor actually drive; the fans, the idiot gauge, or both?

 

The ECT provides a coolant temperature reading to the Engine Control Module (ECM). That information is then used to adjust the engine parameters for the running engine.

The ECM also uses that information to control a relay module that operates the fans. Fan opreration can also be influenced by other factors, such as the A/C running. The information is also networked to other modules, such as the instrument cluster which uses it to drive the idiot gauge.

It is also available from the OBDII port with a code reader that supports real-time monitoring (most do).

My adivce would be to get an OBDII code reader connected (go to Autozone if you do not have one for a free reading) and find out what your true operating temperature is. There is a good chance you are running hot and need a new thermostat.

My other advice is to find a new mechanic.

 

Thanks much. The mechanic idea is also prettyy good advice! :-)

 

Thermostat!!!

 

As a routine PM matter, when replacing any of the hoses, water pump or coolant, replacing the thermostat is advised. It is a cheap PM item that provides a lot of overheating protection and peace of mind. It is also rather easy to get at.

 

Ditto what Paul P said; I had the same thing happen to me!

I replaced the plastic thermostat housing and did a flush & coolant change at the same time. Immediately thereafter, I was having "periododic" engine temp run-aways. (That was before WhiteXKR taught us all that the engine temp and oil pressure guages aren't really GUAGES at all, but rather nothting more than an indicator of "everything's fine" vs. HA-HA-HA-YOU'RE SCREWED!...PROCEED TO THE NEAREST ENGINE REBUILDER!")

My point is it was a very strange coincidence that the t-stat decided to fail at that very same time. I was dumbfounded, and couldn't believe it; after all, my car had only 31K miles! So I verified the t-stat failure the old-school way in a pot of boiling water on the kitchen stove with a thermometer. Didn't open at all!

Change the t-stat!

John

 

200 degrees F + 10 is about where you should feel confortable. Mine stays right in the neighborhood of 195-197 F.