Temperature Gauge Acting up
 

I have a 2002 Ranger 3.0 4x4. A couple months ago I made the repair of the timing cover leak, which is known on these trucks. During the process I went ahead and replaced the radiator, the thermostat and gasket, and the water pump. Recently I’ve noticed the gauge will slowly move down a little bit under normal temperature when I take off and go back to normal slowly after about two seconds. Only does it when I take off after a stop. Other than that reads in the middle like it always has. Not sure if it’s a problem with the T-stat or if that’s normal and I’m just now noticing it.

The other forums were clear signs of thermostat issues, but this just doesn’t seem like one of them.

Any ideas?

It may be that the radiator is now working better, lol

The engine will warm up a bit at idle, circulation of coolant is low, i.e. water pump speed, so coolant sits in radiator a bit longer cooling off more
When you increase RPMs, water pump speed, this cooler coolant is pulled into the engine which lowers the temp, now depending on WHERE the temp SENDER is located on the cooling system you may notice that as a drop and then return to normal

You could check the fan clutch, when you start COLD engine you should HEAR the fan for a few seconds, maybe 5-10 seconds, then it will get quiet as the clutch releases the fan to spin freely because its cold
If noise doesn't go away then clutch is stuck on, which doesn't hurt but it could fail OFF at anytime
If its stuck on then the sudden increase of air flow on the SENDER could drop it a few degrees, long shot at best

No, not thermostat related it can't open and close that fast, it uses WAX so pretty slow to react to changes in temps

Something you may want to check: Do any of your gauges fluctuate a bit when turning on your headlights, a turn signal or stepping on the brakes? I've had some old vehicles like that. Gauges were a bit sensitive to voltage fluctuation. Couple were from corroded grounds... some were from soon to expire alternators... some just did it to do it. ;)

A tired battery and charging system crossed my mind too.

negative. Only after the thermostat has opened up and it’s at normal operating temp and I stop and take off again. It’s not like a surge or anything. Have seen that too 😂

could be that. It’s not a big jump back into place, just goes down a little slowly then works it way back up slowly. But it’s maybe slightly below the normal position and then back to the normal position😂 probably just me being picky.

Sorta relevant
 

My temp issue is different but this looks like a thread I could hijack without too much flaming....

My 3.0 B 3000 temp gauge seems more like an ambient temperature gauge. When weather outside is cold, temp gauge stays down near but not quite 'cold.' As outside temps come up, so does the gauge. It is an educated guess that the thermostat is not closing. The odd thing is that as outside temps come up, the gauge will usually stop going up about where 'normal' running temps should be. Its not until the outside temps go into the high 80's or 90's, and AC on, that the gauge will go on into the 'hot' area. Shutting off the AC will bring it back down to 'normal' or slightly higher. Seems to me that if the thermostat is stuck open, it would run cooler than normal until the temps went much higher.

Mia Culpa
 

Well, guess I was wrong about hijacking this thread; thought it had about run it's course. I'll try another Forum.