This summer, I have recently started having constant issues with my engine overheating while in stop/go traffic and the A/C running when temps are 86F or higher. The temp gauge would quickly jump to the 3/4 position along with my outside temp gauge quickly rising (sometimes it'll read the outside temp at 114F!) When I get some speed or when I turn off the A/C compressor, the engine will quickly cool back down to normal operating temps and everything is back to normal.

I confirmed that both radiator fans are operating normally, except one of them shakes a little while operating, but they're spinning. The engine coolant reservoir is also full, however I did notice my radiator is a bit dirty.

Any ideas on how I can mitigate this issue? I probably won't replace anything major if needed with winter coming soon.

2007 Infiniti G35x Sedan - 173,000 highway miles

Thanks!!

 

The ac puts more load on your engine so it will get hotter quicker. Your radiator fans could be working but not as strong as they should be. Fans have 3 serttings either off, low, or high speed. They should always be on when ac is on. High speed will kick in usually stopped at a light.
The outside temp gauge is located behind the front bumper. The hotter your engine is will give the sensor a false reading.
You could have air in your system. Usually you'll hear some liquid sloshing around behind your dash. Something is wrong as your car shouldn't overheat in any condition unless you want a blown head gasket and a new engine. Best way is to warm up the car then test in the driveway. In my easiest order it could be 1. air in system 2. replace radiator cap 3. radiator fans 4. thermostat

 

It's probably your fan motors dying. I had this problem about a month or two ago and it was fixed with a new fan unit. Mine would only run at the low speed and I confirmed it by putting power to the connectors. After replacing that all is well and it takes about an hour or less to swap out in your driveway.

 

Is there a good way to test if the fan motors need replacement or is power to the connectors the only method? Is there a DIY out there for replacing the motors?

Thanks for your help!

 

Read the FSM

http://www.nicoclub.com/service-manu...7_G35_Sedan/co

See page CO3

OVERHEATING CAUSE ANALYSIS
CO-3

SYMPTOM DIAGNOSIS
OVERHEATING CAUSE ANALYSIS
Troubleshooting Chart
INFOID:0000000000956333
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
Fan assembly
—
High resistance to fan rotation
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


Check all those above and let us know what you find.

Since you mentioned the coolant looks dirty it is most likely due for replacement along with the water pump, thermostat, and fans.
If the radiator is clogged you may need to replace that also with a almost eleven year old vehicle.

And waiting until winter depending on where you are, can cause one to freeze to death during a cooling system breakdown late at night or in a snowstorm

A brand new vehicle comes with all new parts and a warranty.

Good luck

Telcoman

 

There are three relays that control the speed of the fan.

All three off = Fan off
One on = low fan
All on = high fan

Normally, you'd want to test the wiring, relays, and all the stuff as well. But, I just looked at mine and since the engine cooled while driving I went right for the fan assembly. I then verified it didn't run at high speed.

I think there is a DIY for replacing the motors, but they are like 50-70 dollars. Some of them you have to splice into the existing harness. For 30 dollars extra, I just bought a new assembly from eBay. Direct fit replacement and haven't had any issues since and I test that fan prior to putting it in with power to the terminals.