You don't need to pull the glowplugs to check them. Actually looking at them isn't going to tell you anything. All you need is a basic volt/ohm meter. Pull the cover off of the GP relay, black box on driver's side fenderwell. Pull the connector off that goes to the 5 glowplugs. Checking for ohms, put the neg. lead on a good ground and touch each plug's "socket" in the connector. You should read no more than .5 or so ohms. Anything higher indcates a plug on it's way out. A infinite reading would be a dead plug. This check takes less than 5, minutes. I would pay to see anyone be able to pull all 5 glowplugs out in that time.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member