My friend's 2006 B7 started throwing the P0128 code, which supposedly is a thermostat issue. The car has about 60k on it. The temp gauge is stable in the middle of the scale (just like before it started throwing the code). The heating works just fine. The code has been cleared but came back after a few cold starts. Now interesting part that I just learned about is that the mechanic that was performing the coolant flush (about 1 month ago) filled up the system with undiluted G12 antifreeze, when to my knowledge it even states on the bottle to dilute it 1:1...

So my questions are as follows:
1. Should half of the coolant be drained and the system be topped off with distilled water asap?
2. Would running the concentrated coolant cause issues with thermostat?
3. How to make sure that the thermostat indeed needs replacement?
4. What are my friend's options regarding obtaining the new thermostat?
5. Lastly did anyone of you perform a DIY thermostat replacement? I hear it's a pain on B7 because alternator and accessory belts need to be removed. Is anyone aware of a thread showing step by step instructions?

Thanks!

 

I would drain all the coolant & refill with a 50/50 mixture of g12 coolant , reset faults & see what happens.

Most of the time it not a matter of the temp guage location but a caculated formula designed in the software which monitors how long it takes to reach that temperature. If it takes too long to reach temp , the fault code is set.

Depending on what engine you have , you might want to consider a timing belt job if a thermostat is necessary.

 

I don't know how you would drain half. But i would start with a true 50/50 mix and see what happens.

The thermostat isn't hard to replace but you do need to remove the alternator for easier access. Its pretty expensive aswell because its not a typical thermostat, its an entire housing because its electronically operated