Thermostat Wahler or OEM BMW

03’ E46 318ci with 130k miles and no issues with the whole cooling system. Neither the thermostat.

Got the Wahler on my 2008/2011 and it was identical to the MB part except the area that had the MB logo on the original one was ground out.

I was instructed by a friend who had some of m47 and m57, to buy thermostat only original from bmw, because everything else doesn't work as long or good.

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.

The replacement thermostat came from BMW. No problems this time.

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 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.

Changed to genuine thermostat, no change. Needle tends to dip on higher load highway driving, but only occasionally. Obd temp is between 77C-88C.