So I ended up snapping the adjusting rod ring on my w201 after trying to tighten up the belt. I then needed to replace the rod, luckily I had a spare on hand (NOTE: when replacing failed or worn parts always try to keep components of the failed part that may be reusable or come in handy just in case). After getting the tensioner of and putting on the replacement rod I then discovered that my tensioner shock was bad. I can compress it but it would not return. I did not want to deal with a squeaking belt so what i did was put a spring on the rod, sort of like a coilover. The belt is now tight. I believe this may even permanently fix a worn tensioner shock.

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1990 190E 3.0L

Nice - I have been thinking of doing something along those lines.

What spring did you use?

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

I used a spring from an umbrella. Not the large spring, the smaller one as the large one is too stiff. That was all that was available to me because i was not anticipating this. But it worked great.

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1990 190E 3.0L

Hitman, I finally saw your message and replied today.
To add a few comments:

Getting the tension pointer correctly on "zero" is Job One on these tensioners, since that pointer can be rotated to any position, and the belt sometimes retains some pull on the tensioner even when the adjuster rod is totally loose.

After a broken tensioner stranded me, I became pretty anal about checking/adjusting. When I have a reason to have the belt loose I always pop it totally off one of the pulleys to relieve any possible pull on the tensioner. Then, I grab the tensioner pulley and work it back and forth to see if the rubber feels normal: it should give and move both directions, but not have any slack or feeling of slop, and feel reasonably tight at center. Then let it center, and check that the pointer is on "zero" and adjust if needed. Then put the belt back on (which may move the pointer off "zero" but don't worry about it) and adjust the belt until the pointer is correct - about 70% depending on exact year model. When correct adjustment is obtained, try this:
Take you index finger only, and push down on the belt right beside the distributor cover. If you can just get the belt to move down about an inch, and make contact with the small water pipe below, the tensioner is set pretty good.

If you still get squeals, check the belt and pulleys, and maybe check the AC compressor for correct charge; it should show bubbles in the sight glass for up to 10 seconds or so after turning on, then clear up (just an approximate check of course).

DG