Question on the temperature gauge on the dash. It looks like when at the center the eng temp is 180, What temp would the right side white mark be? and when it hits the red mark what would the temp be? At what temp should the fan clutch lock up at ? I got hot one time so pulled the rad and cleaned it. Trying to decide if the clutch fan is working or not. I do not here it come on but I may not be giving it time to because when I see a long hill climb coming I turn the heater on Max so it won't get hot. I have a 2000 Dodge Ram 3500 5.9 24v diesel truck and towing a 36’ 5th wheel trailer.

 

it shouldn't even be breathing hard pulling that little load, let alone overheating. if you don't ever hear the fan then that is a good place to start. good luck

 

Viscous Fan Clutch engages based in air temp .....not coolant temp.
It engages between 160* and 180*air temp .... exiting the back of radiator.

Coolant Temp Scale is from 140*F - 240*F. Straight up is 190*F.
At 233*F you get a Check Engine Light and a warning tone!

RJ

 

If you do not hear the fan at all when its overheating, that is your problem. When that clutch engages, YOU WILL KNOW!!! No amount of radio or heater fan blowing will drown it out. Sounds like a jet taking off... I believe at full lock, that fan pulls 8,800 CFM per minute...

I had mine engage once last summer, wow, it took all of 30 seconds for the gauge to move back down...