MB #603 589 00 40 00 Counter Holder
"Hold the belt pulley with the counter holder when performing this step.
The tool fits behind the waterpump pulley and a portion fits under the pulley from below and a portion fits on top of the belt from above, presure is applied to the handle and the tool faces are brought to bear on the pulley from above and below simultaniously through a cam type action. The cam action allows you to hold the pulley in place while undoing the nuts in front of the fan. You could probably make a similar tool from a piece of flat stock. Get a 12-18" piece of 1/4 X1" bar stock, fabricate a small piece of steel or better still aluminum to fit the contour of the insde/underside of the pulley bolt this to the flat stock with a couple small bolts them fabricate a similar block to conform with the outside curve of the pulley, position and bolt that to the flat stock, leave enough space to fit the tool to the pulley from behind, putting downward pressure on the tool handle will cam the tool head and jam the pulley between the two fabricated blocks securing the pulley from movment as you unbolt the fan bolts from the front. If you've got access to an engine manual the tool and the procedure is in 20-312. Good Luck!
