AudiWorld Forums - Thermostat comparison..... >>

Well, here is a quick, non technical comparison of the 2 thermostats that we use in our beloved TT's. In one corner (right), Audi OEM PN 050 121 113 C, bought at the dealer for $50.26 (ouch!), in the other corner, Wahler (we'll call it 'W') PN 3141.87D that can be found for $17.50.
<img src="http://pictureposter.audiworld.com/62820/sideview.jpg">
As you can see, the OEM part has a bigger bulb than W, which gives an advantage in sensitivity (ejem...) and travel (opening).
The opening that the plunger controls (diameter of the valve)is the same in both, basic differences are travel and bulb size. Now, let's go to the pool...
<img src="http://pictureposter.audiworld.com/62820/210f-fullopen.jpg">
Both start to open at the same temperature of 87C (188F), which is correct. OEM part opens faster than W. By the time they reach 195F both are open (OEM more than W), but the OEM plunger is extended further than W, result: more coolant flow.
At a max temp of 210 (no pressure cooker here), OEM was full opened as W, but there was a noticeable difference in valve clearance, about 3/16" giving the advantage to OEM.

On the cooling side, both were cooled at the same time in the same pool, W closed quicker than OEM, where OEM did progresively move the plug to closed and W did a faily quick movement. Both were closed at the same temperature of 180F

Conclusions: From both parts, OEM and W, OEM did a smoother operation than W both warming up and cooling down as it did have a wider valve opening by 3/16" more than W. The valve size on both parts is the same diameter(26.6 mm), the difference in bulb diameter is 5mm(OEM 15mmx33 mm, W is 10mmx31 mm).The length of the bulb does not look like much, but look at the second pic and you'll see that the spring binds and limits the travel on W, which does not happen on OEM. From the observations, I will choose the OEM part over the W. Now, there is why our cars start to creep up the heat when we replace that part.

Disclaimer: Again, this is my personal opinion, no animals (but me) were involved in the testing and it is just for information, the lab paid for both samples so there is no leaning towards anyone.

Tomorrow's Post: How to replace the thermostat in 15 minutes without removing everything on the front of the motor.

Till next time,

The Lab.