So after seeing about 8 threads with "help car overheating" I've decided to post some of my issues and solutions along with some of the issues others have encountered so that if you found this on a search you can find some help instantly.

Firstly, this thread pertains to 2003-2004 g35's with mechanical fan. Aka fan clutch.

Always remember think safe and use common sense.

Say your noticing temperatures climbing when in traffic or at a stop but normal temps at highway speeds. This can be a number of things, so lets always start from easiest to hardest. The easiest thing to do is to check the reservoir for fluid. Never open the radiator cap when hot as this can cause severe bodily injury. Next up is check to see if you have any obstructions in the path of the a/c condensor. You can grab a water hose and pour water through the Condensor as it will clear dirt and grime that you cannot reach between the fins.

You can now check after everything is dry to see if there are any visible leaks.

So you're driving on the highway and the temps are rising What then?

Well there is again a few variables to check. Sometimes trapped air can cause this issue. But before we get there the first thing to do is check your reserve tank. This tank can always give you clues as to what is going on.

If it's empty, chances are you have a leak or the engine is sucking up the fluid, or you have failed to observe the level and it has run low. If the tank is full and fluid being pushed out... Well, you have a few possibilities your radiator cap could be bad, thermostat is stuck closed, or your headgasket has failed and causing the fluid to overboil.

Trapped air can also mimic a blown head gasket and the only real way to find out is to bleed the system thoroughly.

One observation that I have noticed with our cooling system is the way it works when coming off the freeway. You have to remember as you are traveling regardless of distance the RPM's will dictate amount of pressure and flow your water pump will generate. With that being said; Say your coming off the freeway from an hour drive... Although the radiator temperature is substantially lower than your engine's internal temperature the thermostat will stick open and as your speeds slow down the fluid will begin to flow into the engine as hotter fluid flows into the radiator. I have seen temps go from 172 all the way up to 185 in a matter of seconds. This is due to the fact that your engine's combustion chamber is quite hot and it's the way Infiniti designed the system. So if your having issues with temps climbing once you get off the highway it's more than likely due to a poor air circulation at idle / low speeds. Usually if that's the case and you have a fan clutch it could be a sign of a faulty fan clutch. Although as you drive for long distances the air moving through the radiator begins to drop to ambient temps and it brings the temperature of the fan clutch below the normal operating temperature and as the temps climb the fan begins to grab. Regardless, newer fan clutches work. So always stay on top of this. One member from here cleaned his a/c condenser and it fixed his issue.

I will also address the Pathfinder Cooling mod in a bit.

Before anyone takes this out of context I must say this is strictly an opinion. A very well educated opinion at that.

The design of the intake has a lot to do with the way Infiniti designed the cooling system. The relationship between running rich and heat go hand in hand with one another.

The front two cylinders have always been known to run leaner than the rest of the 4 rear cylinders, to combat this design Infiniti designed the water pump to circulate its principle and coldest fluid around the front two cylinders and then proceed to the other four before heading to the rear pipe which directs fluid to the heater and other sources.

Why is this an important observation?

Well as a tuner you'd LOVE to tune per cylinder instead of by tail pipe stoichiometric levels alone. When tuning by individual cylinders you have to take readings for each individual cylinder by timing, knock, temperature and air/fuel. The "trick" here is the 2003 ECU does not allow you to readily tune the air/fuel much less the timing. So playing with the cooling system and making the other 4 cylinders run cooler than pre-programmed by Infiniti you have altered the way your ECU acts thus forcing the car to run richer. You may notice the car is burning much more fuel. Again, this is only speculation as no one has mentioned creditable data in before and after's for gas consumption with and without the Pathfinder Mod.

Anyhow here is some data that I have collected from the 2003 Infiniti G35 Sedan that I have while using a fan clutch setup.

If you can go to the auto parts store ask then to plug in the obd scanner which will allow them to see live data.

For a fan clutch these are your operating temperatures:

HIGHWAY SPEEDS: 177-183
EXIT HIGHWAY: 183-186
STOP AND GO: 185-191
HEAVY STOP AND GO W/AC:191-194
IDLE W.OUT AC:185-188
IDLE W. AC:188-191

ALL OF THESE TEMPS ARE 100% TESTED. BY ME.

ALSO AUXILIARY FAN KICKS ON AT 203 WITH AC OFF @ 50% power
WITH AC OFF 210 @ 100% power

 

one place to look for leaks is the rear coolant bypass pipe that bolts to the back of the heads. not common, but ive seen them leak before.

 

updated.

 

So here is a rundown

Check your reserve tank

If in doubt clean your a/c condenser

If you notice the lower hose is cold and upper hose hot = chances are your thermostat is stuck closed.

Check for visible leaks

If low speeds temps rise (possible fan clutch failure).

 

#1 cause for this is air bubble trapped in the system

#2 is fan failure

#3 rad cap

#4 T-stat

#5 leak

#6 head gasket


I would address these in this order everytime I work on this cars cooling system.

 

I'm a newb with 2003 sport coupe. I also noticed my engine was getting hotter but no overheating. It started when a noticed a subtle change in engine noise which turned out to be my fans running but temp was ok. Soon after (2 weeks) temp started to increase slightly then went to 3/4 gauge max. I figured I would replace the thermo and flush/change coolant. My thermo was fine but I replaced after conducting a temp check on two new ones. All three (old, new, new replace) just started to open at 185. by 195 they were about 2mm open and they were not at the full 8mm until 200+. At any rate flushing the system and new thermo did not fix. The next step was to pull the rad (easy job) and clean the outside. Low and behold the outside of the rad and air conditioner condenser were packed with dirt, grass, bugs etc. I used some water based degrease and sprayed the rad and air conditioner fins clean. Rad was removed, condition stayed in place, I got a ton of dirt out.

Car now runs great and cool. Even in 100+ traffic with air on the engine runs just below half gage. I cannot hear the fans come on. IMHO the stock rad just has adequate size and any decreased efficiency (dirt) will quickly tax the systems heat transfer. To do this job correctly, the rad should be pulled because I had a lot of debris between the air condenser and the rad.

 

HIGHWAY SPEEDS: 177-183
EXIT HIGHWAY: 183-186
STOP AND GO: 185-191
HEAVY STOP AND GO W/AC:191-194


Hey bud, in summer time, my temperature read is a good 10 points higher than what you have posted above. Indeed, 190 - 195 seems to be the bandwidth where my water temp stays at for the most period of time.

May I ask a few questions:
- What is the ambient temperature that you did your testing on? (I assume you are in Miami and thus a pretty hot scotching summer... )
- What is the % mix that you are using between antifreeze and water?

Thanks again for continuing to offer your expertise in this area

 

hmmm...i am going to have to keep an eye on mine.

 

Ambient temp in Miami is always over 88 degree's ... I tested around 94.

OEM 50/50 mix.


10 points higher is a sign of a failing fan clutch and/or debris between the condenser/radiator.

 

What are the odds of it being the water pump? At an Idle the car runs fine but drive down the road and it heats up fast . replaced Thermostat but it didn't change temps. air flow seems fine. I took off the radiator return line and coolant only trickles out . Not sure if it blew a head gasket but oil is clean and no bubbles in the radiator.

 

I need to know year is it fan clutch or electrical. Type of radiator,

Do you experience the overheating on stop n go traffic or is the problem occurring after you get off the highway?

 

hello, i just changed my battery which reset the radio on my 03 coupe, and drove it for 2.2 miles local since then my temp been rising and i can hear the fan running now.if i drive to a near by store it will rise but driving back temp decrease to its normal level, i would let car run for a couple minutes and nothing happens. What do u suggest me to do to avoid the nag! Please help thank you.

 

305-300-2984...

I figure I put my number out instead and I can be of instant help.

Eric Reyes

 

Thank you Eric i will give you a call tomorrow morning since its already too late!

 

I'm awake from 11am till 6am every day