Have a 97, 142k max. Car over heats when i turn my A/C on. Change water pump 2 months(bc of leakage) ago and my coolant levels hasnt change so there isnt a leak. change coolant twice in the past 2months with Zerex G-05 (50/50 of course). Change thermostat with no change. Change engine temp sensor and it worked for 2weeks. Today it started to overheat again. once i turn off the A/C the temp goes down to half quick. Was searching and came up with a few things, radiator, drier, air in system, or radiator cap. Going to start with radiator cap and going to "burp" the system. Just wanted to see if any1 else has an idea.

A/C isnt as cold as i think it should. A 2002 altima has way colder A/C. Read some where that if the drier is bad the A/C works more and overheats the engine. I havent service A/C and the radiator might be original. I'm sure it has nothing to do with it but the car started to over heat 2days after i switch oil to Valvoline Full Synthetic 5w-30(5Q w/ K&N filter for $24.99) when i was using GTX 5-30. Thanks for any input.

 

First, as you said, you need to bleed the system as best you can.

Also, check for debris blocking either the condenser or radiator.

 

At the risk of being obvious, have you checked to confirm that both cooling fans are running while the AC is on? Also, with the AC on, it should idle higher as well.

You could also check for codes in case there is something wrong that can affect the timing.

 

Definitely check that the radiator fans turn on. Other things to consider/try would be to check for leaves and other junk between the radiator the a/c core. Clean the fins in the radiator and the a/c core as well by blasting them with a hose, reverse direction of the air flow (but you'd probably need to take the radiator out to do it).

 

I check the fans, its running all the time. I turn the a/c full blast in the morning when engine was cold and the fans kick on right away and turn off when i turn a/c off. i just got a rad cap, during lunch ill burp the radiator and take the car to the car wash and power wash the rad and condenser to clean them. Going to check for codes too once my bro returns my code reader( to lazy to do it manually ) which he said during his lunch hr he will bring it to me. Ill report back. If after burping, rad cap, wash, and if there are no codes and it still over heats, what would be my next step? radiator replacement, dryer or something else?

 

Based on what you've reported I can see only two possibilities,

1) The AC is placing a higher than normal load on the engine due to an AC malfunction
2) The fans that normally handle the increased heat generated by the load from the AC are malfunctioning in some manner (spinning the wrong way, spinning too slowly or the blades are malformed).

The fact that the car behaves fine without the AC on, is a big clue. You could try stressing the car a bit without AC to confirm that fact. It should be able to sit, idling, indefinitely with only the primary fan cycling on and off from time to time (depending on ambient temperature).

If it doesn't handle the above stress test very well then there is a basic cooling system fault somewhere. I have seen some modern antifreezes that are not compatible with some older ones and actually react to the point that they create solids that can clog the radiator. To put your mind at ease on that subject, go to a radiator shop and ask them to flow test the radiator. If that checks out then the sytem is probably clean.

Have you tried turning on the cabin heat full blast (with the AC on) to see if that helps to lower the engine temp? If it does then the radiator fans aren't doing their job (assuming the system is clean).

 

Ok, after burping the system which seems that there was no air in system, replacing rad cap and power washing condenser and rad it seem to work. the rad had a lot of crap in the middle so that with cleaning the condenser should have been it. im going run the car harder this weekend and report back. also there was no codes. A/C seems to be colder now too.

*UPDATE*

After doing alot of stop and go this morning with a/c on the car seems to be working great. A/C comes out a lot colder now and its always at half temp. Im pretty sure it was cleaning the rad and condenser, especially the rad bc it was dirty that help the situation. Thanks pmohr and everyone else that gave me ideas. I think the problem is solved but if its not ill update again. Thanks again.