hi

how do you adjust belts and remove or loosen drive belt tensioners on a 94 3l magna when changing belts.

it looks simple but just wondered hoe people adjust and tighten tensioner nuts

Im guessing you are referring to one of the belts that run in front of the timing cover. The rear belt tensioner pulley (Alternator and Power steering) is on the very right top. You undo the nut with a 12mm (might be a 14, cant be sure) spanner and there is a bolt above it that pops out of a bracket facing the bonnet. Tighten or loosen as desired.
The A/C belt which is the one that runs in front has the tensioner pulley on the very left. Same size nut to loosen the pulley and to the top left of it is a 12mm bolt. Dont forget to re-tighten the pulley when your done!
Hope this helps

you have to loosen the bolt in the middle of the pulley to adjust it, found that out the hard way