Hi Everyone,

I have a 2007 S Sedan that is overheating, looking for some guidance.

The car only overheats with the AC on when the car is stopped. With the AC off or if the car is moving with the AC on temp is normal.

I have done the following:

Flushed/bleed cooling system.
Verified thermostat is opening.
Verified both radiator fans are working (and both come on when AC is turned on)
Cleaned condenser.
Replaced fan control module (twice).

I'm a bit stuck and it's regularly over 100 so I'm ready to get this figured out.

TIA for the support!

 

Air in the cooling system?
Pressure test and replace the radiator cap
Follow the overheating troubleshooting steps in the FSM
Did you use the proper and recommended coolant?

Telcoman

 

Thanks for the reply. Cooling system is bleed and correct coolant. After more research the fans may be working but weak?

 

Definitely pressure test the system, if it isn't holding pressure it definitely won't work.

Is there a noticeable difference between low and high fanspeeds? If you are overheating those things should be screaming like a banshee and pushing some serious air.

I would also get a flashlight and inspect the radiator fins at nighttime, have someone shine the light from the engine side and look at the radiator through the grill to make sure it's not packed full of debris between the condensor and the radiator. Inspect the entire radiator not just a couple sections.

Fan motors can get weak with age, the radiator itself can also become slightly clogged due to age and not performing scheduled maintenance flushes every 30k.

 

But why do you not follow the troubleshooting steps in the FSM?

https://nicoclub.com/FSM/G35/Sedan/2...5_Sedan/co.pdf

See page CO-2
OVERHEATING CAUSE ANALYSIS

Symptom Check items Cooling system parts malfunction Poor heat transfer Water pump malfunction Worn or loose drive belt — Thermostat stuck closed — Damaged fins Dust contamination or paper clogging Physical damage Clogged radiator cooling tube Excess foreign material (rust, dirt, sand, etc.) Reduced air flow Cooling fan does not operate High resistance to fan rota- Fan assembly — tion Damaged fan blades Damaged radiator shroud — — — Improper engine coolant mixture ratio ——— Poor engine coolant quality — Engine coolant density — Insufficient engine coolant Engine coolant leaks Cooling hose Loose clamp Cracked hose Water pump Poor sealing Radiator cap Loose Poor sealing Radiator O-ring for damage, deterioration or improper fitting Cracked radiator tank Cracked radiator core Reservoir tank Cracked reservoir tank Overflowing reservoir tank Exhaust gas leaks into cooling system Cylinder head deterioration Cylinder head gasket deterioration

Telcoman

 

Also keep in mind when visually observing the two fans spinning that one will APPEAR to be spinning slower. There are a different number of fins on the fans.