Coolant/Temp oddity

[woodyedmiston]

Recently, I towed a rather heavy load (trailer) for about a 100 miles. The ranger did fine but the temp read out around 5-10 degrees higher for most of the pull. The gauge is a manual aftermarket Stewart Warner guage - not the Ford in-dash gauge. I towed in Drive.

On the return trip, with no trailer, and in OD, the gauge bumped up and down repeatedly from a low of about 185-190 to almost 200. It would stop it for a while and then do it again for a while. There is plenty of coolant in the radiator - although the catch tank the next morning seemed to be down. It has not repeated this in daily driving.

Anyone have a clue what might be causing that? Cavitation with the water pump, localized boiling, compression in the fluid? All cooling system components are relatively new except the radiator - which was flushed about 10k ago.

 

[Earl43P]

I'd expect the higher temp with the load.

The fluctuation afterward sounds like a thermostat.

 

[Ranger5.0]

sounds like the T stat opening and closing. When im working my truck i can see it open and shut on the gauge.

 

[woodyedmiston]

That would explain it - never noticed it on the gauge before but the manual guage is a rather recent addition. I've not pulled something that heave since installing it. I was OK with the higher temp for that reason, but the other thing was just worrisome.

 

[Ranger5.0]

ya, a REAL temp gauge will react to engine temp changes prety fast. Mine will raise a few degrees when i stomp on it and then drop again. if you think about it 180-190ish is prity normal. so goin up a few degrees isnt a big deal. Worry when it pegs at like 270 lol