Engine heats up

[geo0101]

Hello, the problem I'm having is my 1999 Ranger 4WD automatic 3L, I had the heads replaced, water pump, thermostat and belt 1 year ago. Today it's 104 degrees and I went for a ride in it, a/c is cold, temp gauge is normal, started up a steep hill and my temp gauge starts going up, halfway between normal and hot, then my a/c starts blowing warm air. I started down the hill and it returns to normal, back up the hill and again it starts to overheat and a/c is warm. I shut the a/c off engine cools off until sitting in traffic then heats up again. If the compressor is bad would that cause the engine to overheat? I checked oil, no water in it, no water coming out of exhaust, I'm baffled.

 

[RonD]

Welcome to TRS

Very normal for temp gauge to go up a bit when climbing a hill, but use 1/4, 1/2, 3/4 to describe needle position because the wording on the gauge changes.

Normal operating temp should be just below 1/2, and it should go up just above 1/2 when engine is under higher load, i.e. driving up hill
getting close to 3/4 would not be normal and the sign of a problem

Heating up when stopped or driving slowly, is usually a sign the Fan is not fully engaged by the fan clutch.
When moving the air flow thru the rad is doing the cooling, when you slow down or stop the fan is suppose to take over and pull air thru the rad for cooling.
Easy to test this
Cold engine
Open hood and try to spin the fan, shouldn't spin, you can move it but should be tight
Start engine, should hear a whooshing of air from fan being "locked", after 20 seconds turn off the engine
Now try to spin fan again, should spin fairly easy, fan clutch is unlocked

Drive to work or ??, so engine gets to operating temp and radiator is warmed up, Fan clutch works using radiator heat not engine heat, just FYI.
Shut off engine, pop hood and see if you can spin the fan, should not spin, should be tight.

While the fan is mainly used while stopped, when going uphill engine load is increased but speed air flow is reduced in comparison, so slower spinning fan could cause heat up as well

Could also be radiator is getting clogged passages
After engine/radiator are warmed up, shut off engine
Remove the two bolts on the top of fan shroud and pull it back out of the way
Run your had across radiator fins, feel for cooler spots(no hot coolant flowing)
It is a side flow radiator so the Upper Hose(IN from engine) side should be warmer than the Lower Hose(OUT to water pump) side, and fins should get cooler as you feel lower on rad.
Nearest the lower hose is coolest
If you find cooler spots then passages are clogged, you can remove rad and try cleaning/flushing with CLR or vinegar, but it is usually better to replace it.
You should flush heater core and reverse its hoses each time you change the coolant.


The AC has pressure switches, high and low, if engine gets to hot then pressure in AC system can get too hot as well and High Pressure switch will cut off the compressor, so no cold air
I would see about the engine temp issue first, that could solve the AC issue as well