You cannot properly adjust the belt tension w/o loosening the tensioner center bolt. It's pretty well torqued, so you will have to lean on it to get it free. Running the adjuster up and down does nothing other than twist the outer section of the tesioner back and forth. The relationship between the inner and outer tensioner sections is established with the center bolt loosened and the tension adjuster correctly set to the far left of the triangular scale. Anything else and your belt is not properly adjusted.
1987 BMW 325