Ok – here goes, I have an 04 Dodge Ram 1500 4.7L Q-cab SB 4x4. It over heated Fri. 6-20-14 while the wife was going home from church. Had been driving around town on errands w/o any problems — but the last 6 miles the temp gauge went into the “danger zone” but did not hit the “red” zone. She turned off the A/C to no avail -it continued to climb in heat. Not being there when this all happened I stopped @ NAPA & picked up the following >> New radiator - belt - water pump - thermostat - radiator cap - upper & lower rad. hoses. All but the pump was replaced. yes the pump was pulled & inspected. It does not leak > the impeller had no wear, bearing & seal are tight. Soooo i put the old one ( from NAPA in 8-12-12) so it is not quite 2 yrs. old. I have an elec. cooling fan that has done the job since the same date. Clutch went out on the OEM. Finally fired the beast up & it worked great — until i turned the A/C & within 3 - 5 min. it was/is back to the “danger zone” >> increased the rpm to 1000 -1300 to get things moving but it stayed half way 'tween normal 195 -200 & the really hot zone - which it has not done since the clutch fan ‘croaked’ . Sooooo my savvy mechanics out there >> what did i miss & why is me beast heat-n up with the A/C on??? Hep :o
Reported for forum change.
Let me just move that for you.
Off to IMHO. Good luck.
Was the coolant passages flushed?
If the water jacket is clogged with lime-scale and/or rust this would impede the conductance of heat from the engine to the radiator.
2000 Ram 2500 - 5.9L gas with similar behavior. I usually do my own wrenching, but I didn’t have time on this occasion, so I took it to a mechanic I trust. He used an laser thermometer to determine that the lower half of the radiator was pretty much clogged and not cooling. A new radiator solved that problem.
That’s why I trust that mechanic.
Low coolant level is a possibility. The system may have a leak, or may have had a leak related to the components you replaced. Then after the repairs it may not have been completely filled with all of the air bled out. I would make absolutely certain that the system is full of liquid with no air pockets.
The A/C system takes heat from the passenger compartment and disperses it through the condenser which is right in front of the radiator. Thus the engine cooling system has to deal with more heat when the A/C is running, and it’s not unusual for that to result in overheating if the cooling system is compromised in some way.
First off don’t trust the instrument panel gauge to tell the temp. Get a good infrared thermometer and see what the coolant temp is at the return (usually) upper radiator hose.
Do you have a CEL/SES (Check Engine Light or Service Engine Soon) light on? Something like a clogged catalytic converter can cause overheating. Same goes for a timing problem.