Thermostat or Temp Sensor?

[pdfisherman]

Hi everyone,

I have a 2008 A4 2.0T. I was planning on changing the thermostat this weekend, but after reading some other posts, I am not sure if my problem is with the thermostat or temp sensor? Since changing the thermostat is pretty involved, I figured I'd see what you thought. My symptoms are...

Gauge does not go up halfway (to 12 oclock). It usually hovers around a quarter. If it sits and idles and may go up, but once I start driving it drops back down.

Does have Check Engine Light, with "Cooling system performance" code.

I do have heat, the heat works fine.

I would assume if the thermostat was bad, I would not have heat?

Is there a way to test the temp sensor?

Thanks for any advice!

[vvenom800tt]

Thermostat. For sure.

You might as well do the temp sensor at the same time since youll lose coolant. It only takes 1 min to do the sensor.

[danbfree]

Thermostat. For sure.

You might as well do the temp sensor at the same time since youll lose coolant. It only takes 1 min to do the sensor.

TIL! I had no idea it was only a minute more to do the sensor too, thanks for the inadvertent advice!

[Theiceman]

yup stat failure .. 100%

just don't break that stupid clip taking the temp sensor out if you do that , be careful .. bust that thing and you are now hooped .

[Luccatavares]

Mine shows p2181, a mechanic said it is the thermostat housing was cracked. Doesn't leak, gauge working normal. Haven't done yet because they are asking $430. And I'm to scary to do myself

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[Mike@PureMS]

Thermostat is stuck open.

[Luccatavares]

After 15 minutes running the car jumps and I can feel my a/c gets warm for few seconds and I smell the hot water

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[hemantpd1]

Temperature needle goes to the middle when idle for a long time and drop back when you start driving. It thermostat for sure.

[vvenom800tt]

Replace it yourself. 4 bolts to remove alternator and its right there.

[Luccatavares]

I thought about that, what about all the hoses, do I need any special tool?

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[hemantpd1]

For ease, you may buy a cable plier... No other special tool. There is a nice DIY: http://www.audizine.com/forum/showth...lacement-(DIY)

[zeitmorder]

Definitely T-stat. Temp needle was at 1/4 all the time, rarely in the middle. Driving sidestreets all day was fine, taking it on the freeway threw a CEL for "cooling system performance"which i'd clear. Drove it like this for months until I was able to move into a place with a garage. I was even able to pass CA-Smog check so long as the CEL was off Mileage was horrible before I was able to fix it when I did the timing belt job/waterpump while I had the front unbolted.

[inkbybuster]

Same thing happening here. P2181... so I replaced the coolant temp sensor first. No good cel comes back on at random. So now after reading this, next week I will be changing the t stat.

[Luccatavares]

For ease, you may buy a cable plier... No other special tool. There is a nice DIY: http://www.audizine.com/forum/showth...lacement-(DIY)

Awesome DIY thank you

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