"Seizing of glow plugs (also spark plugs) is inevitable when istalled in cylinder head for a long period of time. One technique I know that so far works all the time is by removing the glow plugs when the engine is at operating temperature and using 3/8-inch impact wrench set at very low torque."
Tough to do this at "operating temperature" on the 606 when the intake manifold has to come off. This probably works well on the older diesels like the 617. My 99 E300 has 72K on the odometer and I haven't had a GP problem yet. I'm saving my $$ for when the time comes.
