Hey guys I have a 2003 g35 belt driven fan with one small electric fan. If I idle with ac on for about 15 to 20 min or so my cars temperature starts to climb. I changed radiator with denso brand from rock auto a while back as well as new fan clutch. It went away for a while then winter came everything was fine now its hot again like 90 to 100 so it started to act up. I hooked electronic fan up to 12 volt sorce low and high speed works and they do kick on. I started thinking thermostat but both top and bottom hot so its circulating. Water pump is not leaking and is quiet. Can the condenser be the issue there was alot of crude on radiator when I changed it . I cleaned it a bit but condenser looked brittle I didn't wanna ruin it. Also if I do change it out would this be a good replacement. https://www.z1motorsports.com/radiators-coolant/csf/csf-03-07-g35-aluminum-parallel-flow-ac-condenser-p-34655.html?m=G35

 

Pressure test the AC system, it's probably not holding pressure. Also look between the condenser and the radiator and see if there's a bunch of debris between them restricting airflow.

 

So the ac blows cold untill car engine temp starts over heating then ac shuts off but if I run heat the car cools back down. I cleaned the fins when I put new radiator but they were bent and old. I could be wrong please correct me if I am but if cooling system is 100% working even in 100° weather the car should not over heat right? I read someplace the water pump could be shot but my fins are metal according to the search I did. A friend told me look into condenser that fixed his over heating at idle with ac on. So is the long idleing overheat normal or something is slightly wrong. Completely no over heat while driving and in traffic just if my girl runs into store for 20 min or so it gets hot. I run ac always for baby.

 

The ECM will command the AC Auto Amp to shut down AC function anytime the temp is high enough to trigger the overheat code. This is expected since you're pumping a LOT of extra heat at the radiator with the AC running. You're literally taking heat from inside the cabin and transferring it to the AC condenser which sits directly in front of the radiator.

The AC doesn't create cold air, it just moves HEAT from one place to another.

Step one is to just check coolant levels in the radiator and the overflow/reservoir. Do this with the engine cold.

Step two is to make sure the AC fans are actually running on high, when you turn your AC on it will force the cooling fans to run on high speed. If they're not then you might have a bad relay, there are three located in the IPDM.

Step three is to pressure test the AC system, if it's not holding pressure due to a very small leak (you won't drip water, it will come out as steam) then it won't work properly.

If the water pump is wearing out you will typically see coolant weeping from the left side of the block right near the thermostat housing. That's the outlet port for the weep hole, it will be leaving droplets of coolant on the ground when it does finally go out.

Watch the cooling fans while they're spinning. See if one is spinning slow, when those cooling fan motors fail they don't usually just stop running, they usually just start spinning slowly. This typically causes the car to overheat when parked but will run normal when you are driving and air is blowing past the radiator.

Yes the system should stay perfectly within normal temp range with the AC running even on a 120F day.

 

Thanks for all the info my ac does not leak I have access to a shop ac machine I recycled it out and put 25 min hold and the vaccume didn't drop at all. Now about the fan I only have one electronic fan so comparing speed is hard with nothing to compare it to. The fan does come on but idk if high speed is kicking in . I tested fan does spin at high and low speed with direct power but if relay was bad it wouldn't switch over. I get it. I'll try to see if I can spot the switch from low to high.

 

Sorry that was a typo, I meant to say pressure test the COOLANT system. It should be able to hold like 14-16psi all day. Don't forget to test the cap too. Typically I start with the cap, see what pressure it blows off at. It's stamped on the cap what pressure it SHOULD be holding. Then add 2psi more when you test the rest of the system.

As for testing the fan, since the car will overheat while idling it's easy enough to just pop the hood and watch/listen to the fan speed. Once it's fully up to temp it should kick on the electric fan to low speed which runs pretty quiet. After it hits like 212F it will switch the fan to high speed which is SIGNIFICANTLY louder.

You can also force the electric fan to high speed by just turning on the AC, it always runs on high when the AC is running.

 

try bleeding the cooling system. It sounds like air in the line. Looks full but it's not. on the 08's there is a bleed valve that releases the air. Turn the heat on full and open the valve and fill at the over flow tank- worked for me

 

You do realize that this is almost 2.5 year old thread right..?

 

HAHA, The purpose of the forum is to build info, You never know who you are helping, , the author, a casual reader etc.. I dealt with a leaky sunroof drain for 4 years until someone posted here in this forum..I also dealt with this problem for 3 summers on hot days until I ran across the fix in another forum...All info is good info, you never know who you will help.. Never too late, continue to share useful info..