I've had the thermostat on my M272 engine replaced by an indy mechanic. OEM was Wahler, looking at the original the the Wahler I got, the only difference was the spot where the MB logo was on the original, it was grounded out by some grinding disk on the replacement one.
Reviews of Wahler thermostat
85 votes
I had two Wahlers and they leaked as soon as I fitted them. In exactly the way you described.
I got the wahler one in 2019, that would explain the really slow leak I have.
My Wahler thermostat starts to leak after 4 years. It's not a big leak (only a cup a month) but I'd swap it asap.
Replaced the new Mahle/Behr one with a new Wahler one, and now it runs at 97° under low load and 80° under high load, as it should, and seems to be fine.
I replaced the thermostat myself. It’s in a pretty bad place, hidden under the intake manifold. It took me about 3 hours to get the job done, had to use a mirror to see the screws. Mine was stuck open so the car in winter time wouldn’t even reach 190 F. I bought an OEM Wahler 07K121113B thermostat from Amazon for like 30$, so far has been working great.
My 2007 MKV 2.5 Jetta is still having overheat problems even after changing the tstat to a OEM (Wahler) and the waterpump to one with metal impeller, which works way better than the original.
I installed a Wahler thermostat a little over a year ago and it's still holding strong.
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