Hi there people i really need some help here. I test my radiator and my water pump and both of them seem to be working properly. but my truck keeps on overheating specially when i turn on my a/c and it cools down when i turn on my heater. I really don't have an idea of why that's happening. i been thinking of replacing the radiator and the water pump and see what happens but i don't want to spend a lot of money since times are still kind of hard right now. can some one please help me? i will really appreciated it a lot. thanks. by the way my truck is running with a 4.0 engine.

 

Have you checked out your A/C compressor to make sure it isn't clamming up on you, what is the pressure in the system? You never mentioned the thermostat condition? What about checking for a clogged radiator? Is your water pump squeling? Check the engine oil; is there any contamination, Do you have enough engine oil? Check the radiator fluid; is there contamination, Do you have enough coolant, what is the boiling point of your coolant? How about the Viscus Fan, is it working? Last but not least; what about your engine timeing, could it be off, due to a warn timeing chain, or cam? Lots of questions here. Start with the easy ones first. Check out the coolant system (Thermostat) and then move on.

 

You better quit guessing your self into the poor house and let a shop check it out, give you an estimate then let us hear what it is and the estimate.

 

Start with the simple, cheap things first that are supposed to be replaced periodically. Thermostat and gasket. Then, if you still have the problem and don't want to tackle it yourself, take the whole vehicle to a radiator shop for pressure testing the cooling system.

 

It's a "96", she is tired, somewhat warn out with a cooling system that is have plugged and a failing clutch fan.
Do a coolant pressure test and a flow check first before you start experimenting on it. you will save time and money in the long run.

 

I was just about to ask this question. Mine us a 97 and it also overheats with the a/c on and on the highway. Just changed the fanclutch, next up is the themostat. City driving, temp is fine. WTF!

 

You need to start by checking the belt routing, if it is wrong the water pump will turn to slow.
In the tech section there is a pic of the correct routing.
You also need to check for debris between the radiator and a/c condenser.
Restricted air flow will cause overheating with the added strain of the a/c.