Hi All,
Need help with my car, 2009 G37 saloon with no mods
My car overheats and coolant gauge climbs from 40% upto 80% while ideling or at low speeds
If I give throttle in neutral gear temperature drop to 40% in few seconds
With or without A/C not much difference...
Highway speeds temp is below 40% mark
Previous history suggests tap water in the dadiator for atleast 6 moths, my best guess.

Trouble shooting done so far...
1. Radiator cap changed on engine side, pressure tank cap looks good and tested with spare after market cap
2. Fan control module changed - cos fans were direct
3. Thermostat & water pump changed with OEM parts
4. Radiator flush and coolant filled and stabilized, no leaks or drop in level
5. Extra cooling fan fitted infront of the radiator

Fans speeds seems O.K with rise in temperature, No dash board signs except TPMS,
Fans speeds not tested with computer, radiator blockage not tested yet...

Any one faced this problem kindly help...

 

hey man, not sure on that, but i did have issues somewhat similar on my 11 after i had a flush at the local Nissan dealter.... a few days later and only at idle needle would be at 3/4 at times and stay...turn off ac and it would slowly drop, but once moving all is well, so it only lasted a few minutes etc...took it back to dealer and they topped off coolant and problem never came back...so it was an easy fix for me...looks like you addressed the most logical possibilities etc could it be trapped air?

 

Was the coolant system properly bled? maybe there is still a lot of air trapped in the system

 

^^On that note, how was the system bled?

 

My car has Coolant pressure tank with Radiator Pressure cap unlike overfill tank in other market cars. (See attached pics with radiator caps)..
There is no bleeder valve near fire wall in this car. Radiator bleeder valve is stuck, seems like never opened before. Can't open without breaking.
Bleeding air is simple as per my mechanic. Coolant flow through lower hose connection from pressure tank to system and excess coolant is sent back to pressure tank from top hose connection. Coolant top-up if required after heat up and cool down just once or more if notice change in level of pressure tank.
I am not is super hurry to go to next fix, will keep updating this thread...
Let me know your views & opinions..


Pressure tank with 2 radiator caps

Left cap for Pressure tank, Center one is replaced with new, goes into upper hose joint

Tried this step just to be sure with engine on

 

Mine is doing the same thing however I see dried up coolant everywhere on the engine and wet spots underneath so I must have a leak somewhere. I'm just gonna get a new Radiator.. 144k 11g37

 

Mine was also having coolant leak marks many places, changed few hoses and few new clamps etc.
Even I am planning to get radiator checked for blockage and repair if possible as temporary solution.
New OEM radiator costs almost 1K $ here in Q8...

 

Even though you said the fan speed seems ok, from what you described my first guess would have been that the fans might bee spinning so they pass a visual check but that they are failing and not spinning fast enough...how are the bearings on them any noise or resistance?

for a Radiatoer an aftermarket one should be fine...its not like a sensor or something that require precision...

If you do want an OEM Radiator though, have you tried Parts Souq?...they sell on ebay and through their own website...they usually have the lowest prices including shipping to North America and are based out of the UAE so maybe even less for you....they sell genuine factory parts...

Also, bleeding may not be as simple as the mechanic mentioned you also have to run the fans heater to get the thermostat to open and circulate coolant to the whole system....(you may also want to check the thermostat to see if its gone bad btw it should also be cheap to replace)...

 

Fans speeds increase and decrease as per the temperature. No bearings sound etc. Extra pusher fan is fitted but no major change in temp.
I have not tested fans speeds with OBD tool but fans speed seems good at high speed. (allready changed fan control module, thermostat & coolant pump)
I got a quote of 450$ for Taiwanese make radiator. I might pull the trigger coming weekend and update soon after...
Wish me luck.... hahaha...

 

good luck! please post up if the new rad fixes the problem, BTW I corrected in my post above, you need to run the heater to get the thermostat to open to fully circulate the coolant when bleeding not the fans...sometimes I just don't pay attention to what I type lol

 

Most mechanics whom I talked diagnosed radiator to be clogged with these symptoms and they said it is very common problem with these cars.
I went ahead with raditor repair guy who was confident having done repair before in similar cars.
After cutting open the radiator inlet side tank, there was about 150gm rubbish lower down the fins near drain plug.
Repair guy was telling, mine is partially blocked (say about 15%). Then he showed me a vedio of radiator in which there must be around 1Kg rubbish hahaha...
Now I know why when we tried to flush radiator before through drain plug it was dark brown thick fluid drops taking ages to drain.
Now after clearing blockage and a through cleanup of my old raditor my car is happy even at 50Deg C outside temp needle is not crossing 30% mark...
Removed additional pusher fan also. Do not want to take risk with electrical wiring and fixing later would be impossible here...
U guys don't have to cut open the raditor to see if is blocked. Just open the drain glug and see if it is draining fast and color of the fluid.
Or you tech guys can always get themal camera to know if your raditor is blocked. If I asked mechanics here for same they will call medics hahaha....



Now my car is happy when ideling...

 

Hello MAK, i want first to thank you for posting this issue and for the advise on the solution, i am also living in Q8 and i am having the same issue with my G37s, can you please send me your mobile number on my email address: live.1990@hotmail.com so i can call you and check where you have fixed your radiator? please support in this as i am suffering because of it.

 

Could be air in the cooling system which means you either need to fully bleed it or there is a leak somewhere (where air can get in, while coolant seeps out). It could also be a clog, which would act as if your thermostat is stuck closed.(See below)

Could also be the thermostat is stuck open or closed. If coolant is not moving through the radiator (thermostat stuck closed), it cannot cool properly and the engine over heats. If the coolant goes through the radiator too fast (thermostat stuck open) it cannot cool properly and overheats.

 

You may call Hafeez, 67665340
Thanks,
MAK

 

Yes, thnx for the info

I normally drain & refill coolant every 20k and/or 2 yrs.

How does one flush a block radiator? Or what is best method/tool to use? Thnx