Alright I'm posting this thread after many days of searching several different G35 forums. I have seen dozens of threads with 2003-2005 G35 owners complaining about their car overheating when outside temps are in the 90s and the A/C on when in stop and go traffic. I haven't found a good thread to answer this problem, but did see this solution mentioned once or twice. My G35 also had this problem and this is a free fix/starting point before taking the G to the dealership and blowing hundreds on a new radiator/condensor/compressor that may really not be the problem.

The fix which is outlined below is to take off the bumper and powerwash the condensor/radiator to restore the efficiency of the cooling system.

My 2003 with 130k miles G35 had these symptoms:

1. A/C would work great 98% of the time- would blow very cold with no problems.
2. 2% of the time (always when hot outside and in stop and go city traffic) the A/C would start blowing hot air and then the car would start to overheat. The temp guage would rise to just over 3/4 position.
3. The A/C would start to blow cold again once I could get the car moving to get airflow over the condensor and radiator.
4. NEVER would have any problems when driving on the freeway.
5. I confirmed that both the engine fan AND the electric fan mounted to the condensor are both working 100% normal. Meaning that the engine fan would not be stopped or slowed lightly touching some rolled up newspapers to the fan (this is to test that the fan clutch is not bad). The electric fan turns on once the A/C is turned on and stays on the whole time the A/C is on.
6. No radiator leaks or clogs. Coolant level fine and coolant in good condition.

First thing I did was to take the front bumper off the car so you can get full access to the entire surface area of the condensor.
Good front bumper removal DIY here- https://g35driver.com/forums/v36-diy...r-removal.html



Remove the 3 bolts holding on the electric fan and disconnect the electric plug so you can completely remove the fan.

Remove both horns which are each mounted with 1 10mm bolt. Mark the wires on each horn so you know how to reconnect them correctly.


(Its hard to see here but with the fan and horns removed you have full access to almost the entire front area of the condensor)

Next, leaving the condensor in place and mounted on the car, I took a power-washer to it blowing from the front of the car and made sure to wash the entire surface area of the condensor making sure not to use too much pressure to damage the fins or tubes on the condensor.
(Fins run vertically on the condensor, Tubes run horizontally. DO NOT PUNCTURE any of the tubes or you will be in for a world of hurt and expense replacing the condensor. Be careful with the fins also as damaging them will reduce the efficiency of the condensor)

*Note- I don't actually own or have access to a power-washer so I drove the car (yes with the bumper and all off) to my local carwash at about 1am and spent about $5 in quarters for enough time to wash all the gunk out. I was AMAZED at how dirty the water was that was coming off the condensor. After doing this I could really see how the efficiency of the condensor would have been decreased because of the the gunk and bugs stuck in the fins and between the condensor and radiator.

EDIT: Some powerwashers spray at incredibly high psi. Be very careful not to use too much PSI if you do use a power washer. I took my car to a car wash to do the cleaning and even then the closest I ever got the tip of the sprayer to the condenser was about 12 inches. The risk of pushing small rocks further into the condenser and actually causing a puncture in one of the tubes is definitely a possibility. If you don't want to risk damaging your condenser an alternative method would be to drain and remove the radiator and spray the condenser out from back to front to ensure you push debris OUT of the condenser and not further into it. I was willing to risk the damage and I made sure to be very careful with spraying it out at the carwash.

I also cleaned with a small screwdriver at the very bottom of the condensor a small gap where leaves and all sorts of junk had gathered. The pic below shows how much crap I removed from this gap- and this was AFTER power-washing it all out!



While I had the car stripped down I took an hour to straighten many of the damaged fins on the condensor as best I could. Over time small rocks and bugs bend the fins down and interfere with the airflow through the condensor.

Before


After


While I was at it I drained and refilled the radiator. My coolant really was fine, but while I had such easy access to the drain plug I couldn't resist some cheap extra maintenance. (Disclaimer- DON'T send your wife to get the coolant for you at Autozone. They will talk her in to the $20 gallon of coolant instead of the $8 gallon because "it works so much better than the other stuff". Thanks Autozone!)

I then put everything back together- making sure to test the horns and electric fan BEFORE I put the bumper back on.

After doing this I have had the car out in 95 degree temps idling for about 20 minutes absolutely parked and not once did the A/C start to blow hot or the car start to overheat. Total cost $5 carwash, $20 coolant (ouch) but optional. Much cheaper than anything they will do for you at Infiniti!

 

Wow yours was so dirty! I am definitely gonna have to do this. Thanks for the info!

 

Good stuff, thanks OP.

 

As referenced in this thread: A/C Overheating Help!, the area between the condenser and the rad is very small and tends to get clogged over time.

If you're going to use a pressure washer, be very careful! It's not generally recommended and can cause a lot of damage. Also by just spraying through the front of the condenser, you run the risk of impacting the debris into the fins of the condenser and even the rad, further complicating issues (worse case, necessitating replacement of one or both!). The best is to remove the rad and spray from back to front with a firm but not forceful spray so you don't risk damaging the fins, and do the same thing for the condenser. Or do as I did and carefully split the two as much as you can and again try to spray from back to front. You'd have to do a bit more work and disassemble several things (but you don't need to remove your bumper skin), and it would be more thorough. Also, using an AC condenser cleaner would help getting the fins back to like-new condition.

 

When the dealership told me that the radiator was clogged, and needed replacement, I just assumed that the clogging was internal. And was in spite of changing the coolent at 30K and 60K miles.

Mine had never overheated at all before a few weeks ago, when I was stuck on the interstate for over 25 minutes in 105 degree temps. Then, after suffering with the AC off for 25 minutes, I was able to get going again. Since I had a 2000+ mile round trip vacation scheduled, I took it to the dealership since I couldn't risk overheating on vacation.

 

They also make Radiator Combs

but you need to find one with the same pattern


Not sure if that has it but, just showing you a product.

 

Great work OP!

 

Gordee has some good points. Some powerwashers spray at incredibly high psi. Be very careful not to use too much PSI if you do use a power washer. I took my car to a car wash to do the cleaning and even then the closest I ever got the tip of the sprayer to the condenser was about 12 inches. The risk of pushing small rocks further into the condenser and actually causing a puncture in one of the tubes is definitely a possibility. If you want to take the extra time to take off the radiator and spray everything out from behind is a good idea if you don't want to risk it. I was willing to risk it. I wish I would have known AC condenser cleaner existed before doing this project as I definitely would have used that as well. Thanks Gordee!

I hear you on that one. The first time my G ever did this was about 2 years ago sitting on the vegas strip in 115 degree weather. When the A/C kicks off and it is that hot outside any repair bill from the dealer is mush less painful because you just want it fixed. This was a midnight project and I just kind of decided to give it a go one Friday night since it was a free repair and I had a couple extra hours of sleep I could sacrifice. My wife just had a baby and this is her daily driver so I can't risk the A/C kicking off on her and the baby so I had to get it fixed. So far so good!

Now if I can just figure out why the G is getting about 16 mpg I'll be a happy man. While I was doing this repair I noticed the K&N was wayyyy overdue for a clean and recharge so I did that and will know with this tank of gas if that solved the problem. Hope so!

 

Nice DIY. Mine is still pretty clean, but I've never cleaned anything out and the car is approaching 9 y/o.

BTW, throw that K&N in the garbage because that's where is belongs. Clean the MAF while you're at because the K&N oil had likely covered the MAF elements. Buy NAPA Gold filters (same as OEM) and replace every 15K miles or so. Your motor and MAF will thank you.

 

Hmmm I just might take you up on this. Would you say brake clean would be fine for cleaning the MAF without damaging it? If the MAF is coated in K&N oil would that decrease my MPG?

 

Don't use brake cleaner on the MAF unless you want to replace it. You need to use electronics cleaner only. You can find it at NAPA and other autoparts stores. It is very possible an oil-coated MAF is causing the motor to run rich.

16mpg is fairly low, but if it's been really hot out and you're running the A/C, and you do a lot of stop and go driving, there can be a significant impact in mpg. When the mechanical fan is engaged (usually below 15mph-20mph), it does cause a power drain, as does A/C electric fan which causes a drain on the alternator and ultimately the motor. Also, when the engine is hot and ambient conditions are hot, the ECU richens the fuel mixture and reduces timing to keep the compression chambers cooler to reduce detonation. All this can lead to a 15% reduction in mpg in around town driving.

It's been in the 95 to 105 degree range here in Kansas City for the past 5 weeks. My combined mpgs have gone from ~20-21mpg down to ~18-19mpg because of the heat.

 

Ouch now. Brake cleaner is VERY harsh.

Use electronics cleaner that you get from radio shack and *carefully* spray the small wire inside.




BTW, great post. I went and checked out my condensor today and it definitely needs some debris cleaned from it. I even found a rather large bumblebee headfirst in there. Airflow through the condensor is key, so I guess i'll have to set some time aside soon to clean out the debris

 

If your still having problems then you may have fans not working.

 

Pregnant wife = A/C on full blast everywhere she goes for the last month so it sounds like that could have an effect. I also have the "summer" wheels on the car right now which are 20" chrome heavy beasts. I put the stock wheels on with snow tires in the winter and notice 2 to 3 mpgs better just for that. Still I've owned the car for 3 summers now and 250 miles to a tank is lower than it has ever been. Normal even with the wheels on is 320 to 350. Probably the combo of heavy wheels, prego wife, and possibly an oil coated MAF!

Thanks! Good luck with the project. Let us know how it turns out!

 

I probably need to do this.