I bought my '87 300TD needing a belt tensioner and didn't drive it until I'd fixed (at least) this problem. I'm new to the 603 so this might help fellow first-timers. I had done a lot of searching and reading on the forum regarding this repair and, thinking I might save some time, attempted to do it without removing the fan. After dropping the allen wrench 19 or 23 times between the shroud and the radiator while removing the main tensioner bolt, it turned out the lower tensioner arm interfered with the fan pulley, so I had to pull the fan anyway. After removing the fan (which was actually OK, albeit tight quarters), I wished I had done it from the start. It would have saved me a lot of time. Additionally, as a first timer, it gave me so much more room to see and, therefore, do much better work, which, in turn, made me feel much better about the repair. I also replaced the original style vacuum pump while I was there just for peace of mind. With the tensioner out of the way, this was straight forward and relatively easy. Long story short, if I were to advise a person doing this job for the first time, here are some things I would suggest:

-Search the forum and read the different approaches

-remove the fan, fan pulley, and serpentine belt. This will also help with the first-time belt installation when your done because of the ability to see and move.

-I removed the tensioner pulley with the assembly in my vice. The bolt was very tight and this afforded me better positioning than removal while mounted to the engine.

-Don't forget the spacer (looks like a big washer) that was between the tensioner and the timing chain cover on the old assembly when you're installing the new tensioner.

-If your doing the vacuum pump, rotate the engine on the crank pulley bolt so the pump is not under pressure from the cam circle (or whatever it is called). If I remember correctly, the high sides of the cam circle were at the 12:00 and 6:00 positions, but don't hold me to that.

-I also rotated the engine from the crank bolt to draw the 10cc of clean oil into the vacuum pump. The instructions said to do this with the engine running, but I wasn't sure I could get my wrenches on the fittings with the fan and belt installed. I don't know if my method is acceptable, but it seemed to work for me ok. In retrospect, I imagine the engine could run for this short period without the fan or belt.

Just some observations.

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-RK
'83 240D, auto, 170,000 miles "Old Blue"
'87 300TD, 140,000 miles