High RPM=High coolant temp?

[Sawed-off]

 

I’ve been noticing that my coolant temperature has been running higher than normal at high speeds (75-85 mph, 2500ish rpm).  Around town and slower highways it runs around 185-195, but run the rpm up and coolant quickly rises to 210-215.  It drops down to 185 only a few second after I drop the rpm.

 

I also tested this in 2nd gear locked @ 40 mph/2600 rpm, temp quickly rises to 215 but will fall to 185 in 3rd or 4th gear.  I don’t normally drive around at 2600 rpm, but with 4.10 gears and an 80 mph speed limit it gets close.

 

I recently swapped out the thermostat with a new NAPA 190* because it was not getting to operating temp and I figured it was stuck open.  I also removed and cleaned the radiator at that time.  Now I’m not liking how high and how much it fluctuates.  Could it be the new thermostat is bad? Is there a recommended brand to run?  Or do I have bigger issues?

 

Thanks for the help!

 

The truck is a 2000 Dodge 2500 quad cab short bed, 4x4, 4:10 gears, ATS auto, 60HP edge, Fass pump.

A few pics of what I’m seeing:

[NIsaacs]

Is your fan clutch working?

[Mopar1973Man]

Radiator face plugged? Fan clutch working? Thermostat functional?

 

Strange but true I've been running without a fan altogether the last week and have trouble getting over 188*F. No towing but still climbing 3 grades never even hit 190*F.

 

Edited November 24, 2018 by Mopar1973Man

[Sawed-off]

Thanks guys.  I’m not real sure about the fan clutch, I think I heard it one time climbing a hill while pulling a load in the summer and the needle went almost to the end of the white before it kicked on.

 

I pulled the radiator and cleaned the face when I changed the thermostat.

 

Where should the gauge read when the fan kicks on?

 

I might try a new thermostat and see if that changes anything.  Or maybe see what it does without one. If the temp doesn’t climb that high without a thermostat I would think this one is goofy.

 

Again, thanks for the help.  I think this place is a great resource for these trucks.  I come here and read up quite a bit and have leaned a lot.  

[Mopar1973Man]

Typically it should lock the fan by about 205 to 208F. The far end of the normal range 225F.

[wil440]

3 hours ago, Sawed-off said:

I might try a new thermostat and see if that changes anything.  Or maybe see what it does without one. If the temp doesn’t climb that high without a thermostat I would think this one is goofy. 

 

 

 

with the thermostat removed it won't get warm at all

Edited November 24, 2018 by wil440
misspelling