ford ranger 1990 4.0

[alonsito0114]

Its normal for my truck when i leave it running for 10 mins will heat up to much like 3/4 on the temp gauge
Is the normal can i do anyrhing to fix it?

 

[oilbased]

My 93 4.0 was doing the same thing before I tore it down to replace a bad lifter. When I pulled the thermostat it was just nasty and caked with kurd. I replaced it with a 180 degree thermostat upon putting it back together after I flushed the coolant side of the motor and now my temp gauge doesn't even get to the halfway mark. I'm not saying this is your problem, just telling you about my experience.

 

[RonD]

No, it isn't normal.

Thermostat is good to change but stick with stock 190-195degF model, it will make engine last longer, and get better MPG.
Ford temp gauge is about 210degF at 1/2, so in normal operation it should be just below 1/2, when pulling a load or driving up a longer hill it should go just above 1/2, 220-225degF
Running an engine cooler may sound like a good idea but if it was true it would be very very easy to run an engine at 100degF, problem is it isn't good.
Point of the thermostat is so engine will run at a higher temp, after many years of research by S.A.E.(the oil guys) and Ford, the 195-200degF coolant temp range was found to be the best for normal operation, cleans the oil better(evaporates contaminants) and gives cylinders best temp for MPG

Your Fan clutch or radiator could also be the problem.

After engine, and rad, is warmed up shut off the engine.
Spin the fan by hand, it should be tight, and not spin after you let go of blade, it will turn just not spin free.

Now remove the 2 bolts holding top of fan shroud, lift it and slide it back over fan.
Run you hand across radiator fins, top to bottom and side to side.
There should be no cool spots, should be nice even heat across and down, a cooler spot means no flow so clogged area.
Also check front of rad, clean out any mud, dirt, or debris.

 

[enjr44]

Only at Idle? Not going down the road? How about while in stop and go traffic? Thermostat does not cause over heating unless it is doing it all the time, i.e. not opening all the way. It would not cool back off when driving.

And it should not be doing it. I leave mine running with AC on to cool my dog in temps over 115. The needle never moves.

My guesses are: Fan clutch is bad (doesn't lockup when rad get hot). Or, radiator is partly clogged (some of the tubes are blocked, reducing flow). Or, radiator/fan shroud is missing (fan can't pull air through rad). Since it is only doing it when there is no or little ram air flow past the radiator (like when driving).

Ron, you beat me to it!!!!