88 300E Belt Tensioner...I'm confused

Been surfing the site and can't really find my answer.

I replaced my alternator last weekend, no problem there....but the belt tensioner threw me off a little. I have the adjuster nut behind the reservoir (more on this later) however I saw no nut on the tensioner pulley, mine had a plastic cover on it. I removed it and had to use a 8mm hex socket/wrench fit into the pulley to lever it back an inch or so so I could get the belt off/on. Had to hold tension on it while pulling belt on/off..lotsa fun! There was no bolt that I could see. Loosening the adjustor nut didn't seem to help any at all. I also didn't see any tension indicators on the pulley.

When I managed to get belt back on, tightened down the adjustor a tad too much, yep it popped. However, the belt is still pretty tight because of the pulley.

My question is could I have a new type of tensioner on my car (I bought it used)and if so am I hurting anything by driving it w/ out the adjustor bolt? Also what do I need to replace to get the adjustor bolt back into play, I assume I broke whatever it was attached to. Thanks!



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88 300E (plus used to have 72 350SL, 83 240D)
Dad's got a 99 ML320 & 93 300SE...we're a Mercedes family !