ModRofl

Yet again I'm having a new problem with my car, something I'm getting used to by now considering it has over 125k miles on it.

Anyways, after the check engine light came on yet again, I have used an OBD scanner and it gave me a P2181, which is related to the Cooling System Performance. In my case it seems undercooling.
The gauge on the dashboard usually seems to be showing between 25% and the proper operating temperature (50%), while driving it does occasionally get to 50% but usually stays within 35% region. But never above 50% which is good.
The heater seems to work fine, but it is of course it is summer, so perhaps it's not as easy to determine.

I checked the coolant level, added the small amount necessary. But as I predicted that wasn't the cause of the problem.
As it stands everything points to the fact that the thermostat is stuck open.

Anyways, the reason I am writing on this forum, is for two questions.

1. What are the symptoms of a fault sensor? as if that's the cause I would make the repair myself.

2. Is there a big danger of driving with an under heating engine? It doesn't seem to under heat too much since it does usually get to the operating temperature after a while, but I am looking to get rid of the car in perhaps a year or so, and was wondering if a catastrophic failure could occur from under heating. I won't be able to get much for the car anyways so was thinking of just driving the way it is. I am quoted around 600$ for the thermostat replacement.

3. If the thermostat is getting stuck open, is there a danger of it becoming stuck closed? Which is well obviously would force me to seek replacement asap.

Side question: Is there a point of purchasing a VAG Com? I have a very cheap OBD II reader which is good enough to give me all the codes, and allowed me to make a few repairs myself already (PSV valve, gas cap, spark plugs) but does VAG Com have more functions that it would be worth purchasing?

Thank You!

SMac770

https://itstillruns.com/symptoms-the...n-7606570.html

I would look to fix it while it's not stranding you, rather than something suddenly changing and you've got no ride till it's fixed. It's not a particularly tough thing to change, but at that mileage you might want to change the whole trio (pump, thermostat, temp sensor). Well, except you say you're unloading the car soon. The pump adds a decent cost, but just the thermostat kit is not expensive and you can do it yourself, if you're handy in that manner.
https://www.audizine.com/forum/showt...p/858922-P2181
https://www.ecstuning.com/Audi-B8_A4...ng/Thermostat/

As for resell, as long as the MIL is on, it can't pass emissions (here in ATL, at least). So it would be a big ding on price, assuming I wouldn't just pass it over altogether.

If you feel your current tool set accomplishes all you think you need, then good. As long as I or a family member own a VW/Audi, I'll have a Ross-Tech VCDS tool.

ModRofl

Thank You for the references! Yea I was thinking of doing the repair myself initially having watched the video but problem is I don't necessarily have all the tools to get this done without extending the time of the job by hours. But Thank You again, I'll keep this in mind.