Our sedan keeps overheating. It is an 03 G35 sedan. I have replaced the thermostat, radiator cap, and checked for leaks. There are no leaks anywhere. I took the it to infiniti here and had the whole system flushed and purged for air. It is not blowing any smoke, and is not losing coolant. We did a test to check the coolant for exhaust gas and could not find any. The electronic fans are coming on as they should. The car drives fine and the temp guage will stay right in the middle while in motion. On hot days if you stay at idle in a parking lot or drivethru it will rise. We idled for 15 minutes or so today in the 83 degree humid weather and the coolant overflow tank boiled up and over, and the guage was nearly topped out. I am at a loss of where to try next. any help would be appreciated.

 

This has happened to my G20 previously and the thermostat sensor was the issue.

 

wouldnt this just cause the guage to read wrong? The fans work at idle but it still gets really hot.

 

03 sedans have fan clutch I thought ??? At least my 03 does

 

ours has electronic fans

 

coolant was changed out? if a leak test had no problems then...

water pump, bad thermostat, or radiator cap isn't working

rad cap test - the car at operating temp will pressurize the system and the upper radiator hose should have a lot of pressure on it. you should not really be able to squeeze it much.

Thermostats can be bad even when they are new. It is best to test them before you install them into the car. This can easily be done by putting them into a pot of water and waiting for it to boil. Using a thermometer you can measure that it is fully opened by the time it should. Mechanical fan clutch cars are 180* thermostats and the Electric fan operated cars are 170*. I believe that is when they start opening not fully open. Takes 10* or so for fully open.

It is also possible that your water pump is going out and isn't pushing water efficiently any more. It could be cavitating due to AIR IN THE SYSTEM. These engines are notorious for having air bubbles that are hard to get out of the system, even with a full "flush". Does your lower radiator hose get HOT? once car is up to operating temps you should be able to grab that hose. Not only should it be hot but it should be very firm with pressure too.

There are several threads about burping the system but the quickest and easiest way is to use a spill proof funnel. I would ensure that you have done this MULTIPLE times before you move on to anything else. Especially since you have opened up the system.

 

Radiator cap has been replaced and the system does pressurize fine. The system was first flushed and bled at firestone, but the problem persisted. I then took it to Infiniti to have it done there, and was assures all air was out of the system. He ran temperature checks on it in the shop and could not get it to overheat. The fans were coming on as well.

The car does fine while driving in town or anywhere else. It does not start to overheat until we are stopped for a prolonged amount of time. On a hot day in a drivethru it will do it. Stop and go traffic is fine as well. Im at a loss of what to do next.

 

Sounds like you have a fan problem - could even be intermittent.

If it only happens at stop & go then you are not getting enough air through the radiator

Next time the needle starts to move jump out and check BOTH fans should be on full speed.

It could be that your radiator is blocked and not flowing well

 

Yes, thats the thing. I checked this yesterday and both fans were operating at full speed. This is driving me nuts! haha.....would the coolant temp sensor even contribute at all? I assume thats what turns the fans on and off.

 

yes, the temp sensor turns the fans on/off so that could change it if its malfunctioning.

Both fans were engaged on high and pulling in air WHILE the car was overheating?

If it were me, I'd hook up an OBDII scanner and watch what is happening in real time. It will be the quickest way to help diagnose your issue. the dealers CONSULT II would be the best option but good luck getting one of those!

 

Ill try and replicate the issue tonight after my wife gets home with it. Ill check on the fans again as well. Thank you for all of your help so far!!

 

just update the thread with your findings. Mostly we need to know what the fans are doing when the needle starts to climb past normal.

 

The car is still overheating. The fans are coming on and are on when it overheats. It is getting how and the coolant will boil in the overflow tank. Both the upper and lower raciator hose are hot. It is 100 degrees here in Nebraska today, it was upper 90s yesterday and it did not do it. Im at a loss for words. Please help me!!!

 

Keep us posted. I think I have the same issue. Mine had the mechanical fan however..

 

You have no mechanical fan, and you're an 03? maybe I missed that you did have it.

I recommend: buying a lisle funnel and attempting to rebleed.

In my time attempting to bleed, here is what you should do:

1) With car cool, attach funnel about half full with coolant.
2) Start car and get to operating temp.
3) Rev a few times, and squeeze upper hose. Repeat.
4) Go to heater bleader valve (the screw at the heater). Open but do not remove. Just open it enough until fluid comes out.

I recommend doing this on ramps or jack stands.

I had to bleed my car 3 times to get the heat working. If you try to bleed without the funnel at all, I can see how a large bubble could be trapped. I know you have an overheating problem; just trying to empahsize the air issue on the VQ.

The reason to use the funnel is to make the funnel's contents the highest point in the system to aide air pockets to escape.

I would double check the thermostat. Did you overtighten? Just wondering.

How many miles? When you drain, is there any debris in the catch pan? We're trying to figure out if you have a gummed up radiator. I haven't heard of too many WP failures on the VQ, but it's possible.

Does it stop overheating once you get moving again?