I am planning on replacing the belt tensioner, tensioner shock, idle pulley of the 190D OM601 as it is squeaking. I thought it is a 30 minutes job but I am dead wrong. It seems there is not enough clearance to slide out the tensioner because the water pump pulley is in the way. So I think the sequence would be:

1) drain coolant, remove radiator.
2) remove electromagnetic clutch fan
3) remove water pump pulley
4) remove the tensioner

Am I correct? It is such a convoluted job. The tensioner is not doing much. It has a bearing but it is kind of oscillates to adjust the serpentine belt tension. It is a stupid over design IMHO.

Questions:

1) How do I stop the water pump pulley from spinning while I remove the 13mm bolt?
2) Is OM603 the same or similar? My 87 300D is squeaking too.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.