Driving my newly purchased used Ranger home from work one day (93' 3.0L 2WD 5spd), I noticed the temp gauge slightly above half, then would drop to 1/3rd - hang there for a while, then climb back up and repeat the sequence. Not rhythmically so I thought it was a bad t-stat.

Trying to drain the radiator and not being able to, I discovered 3/4 of radiator was clogged from loose scale.

I flushed the heck out of the original radiator and engine, put in a new t-stat and also put in Prestone Super Flush and drove the truck for 3'ish days (~ 6 hours total).

Tonight I drained the coolant, flushed the cooling system 3x with purified water, then installed a new radiator and filled with ~ 60% antifreeze/40% purified water, burped the cooling system and shut it down.

Later I went for a drive on the freeway - and saw the temp gauge kind of doing the same thing! It wouldn't go past the halfway mark, but it would definitely swing between the 1/4 to 1/3rd. Again not rhythmically so I don't think it is the gauge regulator.

Is this typical? The radiator and T-stat are new, fan clutch seems fine. No scale came out from the 3x flushing I did tonight (I think I got them all from the original flush 2 weeks ago). No AC condensor in the way of airflow to the radiator.

Where does you temp gauge sit when fully warmed up? Does it 'move' around?

TIA,
Dave

 

Maybe the temperature sending unit is flaking out. It's the single wire sensor up near where the T-stat housing is. Not terribly expensive and rather straightforward to replace.

 

My stock ranger gauge fluctuates quite a bit. Not as much as yours though. It will stay a tick below N and then sometimes move up to R. I put an aftermarket gauge in and it stays at 178-182 all the time.

 

Mine never moves. Well obviously as it warms up, get's to about halfway between 1/4 and 1/3, then just sits there.