A year ago I noticed that the engine cooling fan would stay on high speed even when not required because of high temperature. After shutting down, operated normally on restart. Hydraulic oil and filters apparently had never been changed (9 years and 67,000 miles). Had oil and filters changed and seemed to operate normally. At about 75,000 miles noticed that the fan speed was surging at idle (engine idle speed was normal). Although the fan no longer surges at idle, I notice that at highway speeds the coolant temperature bounces between 183 and 192 degrees. Currently 77,000 miles, ambient temperature is in the 40s and 50s.
Your thoughts?
Don
You DO want some coolant temperature variation. Said another way, you do not want the fan on high speed until at least a couple of degrees above where the thermostat is fully open.
9 degrees F is perhaps a few degrees more spread than normal, but 183 sounds low for a 2009 Cummins engine (check with Cummins for your engine serial number) AND it may be reasonable to question the gauge accuracy.
192 will sure do no harm to the engine.
Hi Brett,
Thanks for the quick reply. I actually wasn't concerned with the temps because I knew they were well within what is considered normal. The bouncing in temps from 183 to 192 and back within a few seconds seems abnormal to me. I have not noticed this before. It led me to wonder if the fan was actually surging.
Don
If this occurs within a few SECONDS, I suspect a sender/gauge or perhaps just a poor or loose connection on the sender unit.
It will take more than just a few seconds from when the fan goes to high for the coolant temperature in the radiator to cool, AND for that water to circulate through the engine to the sender unit.
Of course. Why didn't I think of that :facepalm:
I will check it out.
Thanks for your help!
Don