My Yeti had a problem with cooling, namely not getting up to temperature and although replacing the thermostat did improve the problem, it didn't entirely cure it! I even replaced the temperature sender which is shown as being a 4 wire type but in fact is a 2 wire type. It did get to the 90 degrees eventually but could take a distance of between 18 - 30 km's. Anyway, getting down to brass tacks after lots of searching and head scratching I found a couple of people who had had similar problems which turned out to be the "second" thermostat in the pipework to the DSG oil cooler, so I bit the bullet ordered one and fitted it and voila the car was finally back to its former glory! The original was like a piece of pipe with no restriction whatsoever when blowing through it. (The Bakelite from within had disintegrated on the seat to the thermostatic valve). Not good on a car that has only done 73,000 km's! The part number is 1K0121113A and took around 40 minutes all up to replace including removal of the air filter box, taking care not to damage anything when releasing the hose clips. I did loose a tiny bit of coolant and topped up using distilled water. I apologise if this has been covered already, but I feel so relieved to have got down to the problem. My local V-Dub man had never encountered the problem...Cheers Rick in Oz