Skip to main content ↑ ↓
Topic: 2002 ISM runs cold (Read 361 times) previous topic - next topic

2002 ISM runs cold

I've been monitoring a potential problem for a while now.  My engine never seems to want to get over 175 degrees as reported by Scanguage D even when operating in ambient conditions in the 90 degree range.  I came to the conclusion that my fan controller must have gone bad since when I stop and check the fan it's running at what seems to be high speed even though the engine is under 180 degrees.  Well today I checked the fans after start up and they were running at low speed; slowly spinning.  I stopped the fan blade with a block of wood and it remained stationary until I gave it a push and it began spinning slowly again. When I unplugged the fan controller it definitely jumps up to high speed and when I plugged it back in it slows down again.  So my fan controller does seem to be operating except for the fact that it's running at high speed at 175 degree engine temperature.  So what would cause my engine to consistently run cold?  The obvious answer would be a thermostat stuck open but that wouldn't explain why the fans go to high speed at less than 175 degrees?  Being the skeptical sort, I'm a little reluctant to believe that I've got two simultaneous failures (thermostat and fan controller) but stranger things have happened.  Is there any way to positively confirm that the thermostat is bad because it's really not that easy to get to and I'd rather not just engage in a parts replacement strategy.  Last question; is there any harm in running the engine at consistently low temps, albeit only about 5 degrees too low.  I understand the drag of the fans on the engine and the loss of fuel economy but other than that is there any potential problem for the engine?

Re: 2002 ISM runs cold

Reply #1 –
I prefer running my engine at 190 and my fan controller is set at 110. If you have a 180 thermostat the fan
controller should be set at 190.

Re: 2002 ISM runs cold

Reply #2 –
There is some coolant flow that bypasses the thermostat to go to the transmission cooler. That combined with the fans running can keep the engine below the thermostat opening point.

The fan controller can work at startup but then fail after a few minutes. Thats what happened to mine. Check the fans after it has been running for a few minutes and see if they are still slow.