Thermostat Wahler or AISIN

In the past and up to several months ago, I’ve always gone with Saleri (Italy) pumps and Wahler (Germany) thermostats for the M54 and have had great results.

I had a wahler thermostat and my temp range was 93-96

I got a Wahler thermostat once who was the OEM maker for MB, the only difference between the Wahler and the old MB one was that there was a spot where the MB logo was, on the Wahler one that logo was gone, looks like it was there, but someone with an angle grinder scratched out the MB logo so it probably came off the same line that made the MB part.

I have had a car not bleed properly/ run hot (but not overheat) only when using the wrong thermostat. Replacing it with Wahler fixed the issue.

A proper Wahler thermostat is what solved it.

New thermostat (Aisin brand), fresh oil, fresh coolant, replaced at that time. Coolant system bled well. No leaks. Heat worked flawlessly. AC worked after the swap. Overheated the drive home after that swap, turns out the radiator fan module got fried on the final drive (it was above 250 on coolant temps before replacing the engine, on a 30 minute, fast, highway drive). Ordered a new one. Everything working perfect now at the right temperature points. Engine times reading perfect too (watching live data). On a 30 minute highway drive tonight, returning home after the same drive 2 days ago with zero issues, it overheats again. Radiator fans are working. The one thing I changed during the drive was turning down the heat from HIGH to 75. No more than 10 minutes later I hear the bubbling in the heater core area. Take my exit from the highway, and the red temp light starts flashing, temps read 239, and the bubbling worsened. Temps stayed above 228 until I made it home from my exit. Worse at red lights. Turned off for 10 minutes, turned back on, temps went up to 232 at idle, holding steady. Lower radiator hose read 102 degrees, upper hose reads 190.

I recently changed the thermostat on my dad's car as well, I went with a wahler, and I'm observing the same things.

I decided to try another thermostat, this time a Wahler and nothing has changed as the car will still not get up to temperature and no hot air.

I changed on mine 2-3 months ago with a new one from Wahler/Borg Warner and now it's leaking through the connector.

I have experienced same with Wahler thermostat.