Hi all,

I'm new here , and really hoping somebody can help me with my G35 2008 VQ35HR, Middle East Specs .

I've got a strange , what I think is an abnormal temperature fluctuation on my coolant temperature gauge. After about 20-30 mins of driving at 2500 - 3500 rpm , my gauge moves from the normal resting position, just above the first solid bar ,to the next thin bars , at most. It returns back down once rpm's are lower. This happens sooner when ambient temperature is above 43C , but can still happen anytime ambient is over 35C. It can also happen after coming to an abrupt stop after a highway drive. At idle , stop & go , trips less than 20 mins or any low rpm driving it will have no problems.

As part of a pre-purchase repair (I am the 3rd owner) , the thermostat,heater hoses were replaced , coolant renewed , radiator cleaned , fan's lo/hi speed verified ok.Caps & clips checked. No visible coolant leaks. Oil is clean , coolant is clean. Combustion gas test done no problems.

My first thought was that I've got air in the system , but no luck in trying to bleed it - the bleed screw is non existent , its just a straight connector on the heater hose. The heater blows hot , seems to be working fine and no weird bubbling sounds. And apparently on this gen to bleed the system one needs some specialized vacuum tool.Also upon looking at the parts diagram , i noticed that this regional model has a pressurized coolant expansion tank (with a pressure cap) So i've got one seal cap on the radiator , and one pressure cap on the coolant expansion tank.

I've visited a couple of garages to help and mechanics' guesses on the solutions are:
- Change the coolant temperature sensor
-Change the radiator , its not able to cope.

And ofcourse the usual in this region when this happens:
-Delete the thermostat it will run cooler (no way im doing this )

I'd rather not just throw parts & funds at it , before figuring out the problem (if i do have one?) , and I'd prefer not to visit the(only 1) stealership to diagnose/fix , as they literally require a kidney as payment services (probably 50% of the car's market value)

I've tried a couple of budget OBD2 scanners , to verify real-time ECT values to correlate gauge readings/calibration/weight , but none of them seem to be able to read the PIDs. I tried the same scanners on buddies' north american spec G's, and they worked well. Will try to borrow a pro scanner from a mechanic soon.

Can anyone please help with this.

Thank you

 

As long as your temp doesn't go above half gauge, enjoy your car is running on the cool side! If you still think it's necessary to trace down your gremlins have your coolant system pressure tested by a Radiator shop! They'll find your issues (if you have one) and replace only those parts needed. Dealerships chase their tails when it comes to coolant issues and replace everything but the steering wheel.

Gary

 

It actually looks like under normal operating conditions it's running too cold and when it finally bumps up THAT is where normal operating temperature should be. Never delete a thermostat, it delays the engine from warming up properly and you can have significant engine wear due to unexpanded metal.

 

Thank you Gary & Cleric.

After feeling around

The "normal" operating needle position on whatever spec we have here is this - double checked with another G at a garage.




And on US units its this .


Both specs/versions are in 50/50 availability in the region due to imports.

Super confusing - no idea why they have different gauges/calibrations on the same MY. , even markings are different.!.

Anyway, so the fluctuations i mentioned in my previous post were unnerving me , but I guess i shouldn't worry..

Thank you both again for your responses. I'll keep a close eye on this

P.S two very common things ive seen in my 15 years here
- Thermostat deletion and the use of a 50wt or 60wt oil when an overheat condition occurs. !!

 

Just so you know both are wrong! Even a 160 degree thermostat is not advised for our rides, last time I ran one that cold was in my Datsun 510 and the real issue was clogged radiator. Heavy weight oil won't solve overheating but will sure eat up your HP!
Like I posted if you don't trust your temp gauge have a radiator shop verify that it's correct or not! Won't be expensive, they might even do it for free since it's so damn easy!

 

You can also use an OBD2 scanner to read the actual temperature data being sent, it should be around 210 or so degrees on a really hot day.

 

Agreed gary ..just pointing out some things ive been seeing , no chance i would do either of that. I'm using an OEM thermostat only.

/

I intially tried reading with a generic ELM327 scanner. It connects and lights up , but can't read the PIDs
Tried the same today with a borrowed Autel 319 , same issue. It reads the protocol , and shows a connection , but cannot read any sensor data. Even the check engine light option is "not available"
Strange , these 2 scanners work on at-least a basic level on every other car ive tried them in including imported G's .

Not sure what im doing wrong..

.Quoted around 170 US$ for a cooling system pressure test and temp verification from a few independent garage Will hang on for the moment.

 

I use the BAFX bluetooth adapter and the app Torque Pro on my Android phone, I know it reads temp (and everything else) on a 2006 G35. I don't know how to set up a custom PID for temp for your scanner though.

 

Gary,

It was a partially clogged radiator .Gave my rad to a rad/condensor cleaning shop.( I guess rodding and flushing).


It now runs at a normal temperature . Highway speeds and it's pretty constant. During severe stop and go the needle shifts ever so slightly when the fans come on and off, as opposed to earlier wherein it would climb up and up and fans would be on full blast for a long time.

A pressure test didn't reveal this earlier. A flush was done earlier and it looked clean as well... wish I had figured this was the culprit...oh well.... .

Touch wood things are fine henceforth

Now i only wish this sauna of a summer would end!
​​