Reviews of OEM Volkswagen expansion tank

The expansion tank with 'mit Silikat' sign has silicate bags known to split and block the heater matrix with silica crystals, potentially costing thousands in repair bills. This design by VW was an attempt to prolong coolant life.

Good news is that none of the sensors leak out from the O-ring seal with the new tank, so I do think there could have been a problem with the yellowed out old tank, perhaps slightly warped/deformed.

Those tanks are cheap and very easy to replace, also if you don't get a lot of air in your system they work just fine. So slap a new one in there and no worries.

Yes, replacing the expansion tank corrected my issue. Leaking or venting from that tank is not normal, if the system builds up to much pressure it should release from the pressure cap.