I have a 2008 g37s 6mt I just bought it and I'm going to have the mechanic at the dealership who sold me the car look at it. The dealership told me the mechanic replaced the thermostat but I still get the p0128 code, and I tried to bleed the system the best I can. Bleeding did make a huge difference , but I'm not sure if the coolant is supposed to be topped off from the radiator because the reservoir gets past max on its own which I'm guessing the car doesn't need to be topped off.

when I remove the radiator cap when the car is cold the reservoir bubbles like a bunch of air is being released. Is that normal? , and the coolant is not at the top anymore.

I need help because I believe that the mechanic doesn't know what he is doing.

 

Find a different shop / mechanic. Not sure what else you can do other than flush the whole system.

 

Bossman did you figure this out? I have same problem!!!

 

Here's a great DIY on site~
https://www.myg37.com/forums/d-i-y-i...placement.html

 

get the coolant funnel thing works like a charm easy to use and let the system bleed itself

 

So i bled the system with the funnel and it seem to be a bit better. was ok for a few days then CEL again. Same p0128. I replace the original thermostat and replaced it with the aftermarket mishimoto thermostat but still having the same problem. really need help!!!

 

Is your Coolant reservoir bubbling & are you overheating?

 

Sorry for just responding . No i have no overheating, no bubbling at all. So now i am thinking its the coolant temp sensor. But honestly i have no idea where it is. I cannot find anywhere on internet where its located. frustrating man

 

It's on back side of the head toward driver side. Grubbs is emailing the part spec sheet that shows where it is part cost is 41 bucks

 

Holy Crap man.. So I got to take off the intake manifold to get to this thing? Man that sucks!!!!!

 

It's not that bad you might as well change plugs and clean throttle bodies while you do it

 

Really sucks man!!! but I cannot see any other issue it could be. Unless the Mitshimoto thermostat is not working properly

 

Make sure your drain line that goes to the over flow plastic tank isn't clogged

 

HUH!!! Ok i will check that. Thanks. Any other things I could test before taking the intake off

 

Replace radiator cap