Oxy-Acetylene torch otherwise known as the "Heat Wrench" works wonders here. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Harry Hoffman
Sent: Tuesday, November 23, 2010 9:41 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Rusted on O2 sensor

Hi All,

I'm trying to remove my o2 sensor but it's rusted in place. I've tried
quite a bit of liquid wrench, along with a set of locking pliers and a
hammer. No dice.

How do other people get the sensor off without destroying the cat?

Cheers,
Harry