603 vacuum pump question

[MarkWells]

Hello guys,

I am getting ready to replace the belt tensioner on my 603 and started reading about vacuum pumps. (the archives are a great resource!). I thought "what the heck ..." and pulled mine off out of curiousity while everything was easy to get to (radiator is out).

I was glad to see the cam that drives the piston was in good shape. You can see a witness mark where the piston bearing rides, but it is smoothe. The bearings seem in good shape...no excess play or visible wear. I started to put it back on for now (I've spent a $1000 recently on 4 Dunlop Sport A2's, 4 Bilsteins, wheel bearings, converted solid rotors/calipers to vented since my brake pads/rotors needed replaced anyway). Then I came across this ...(thanks Dave)...

http://www.meimann.com/docs/mercedes/OM603_vac_pump_mod.pdf

"Engine cannot be switched off when cold..."

I have had this problem during cold weather and it says it is due to a damaged piston vacuum pump. What is damaged that causes this? Something worn...faulty design? As you can see, it still has the centering sleeve that is to be pulled and replaced with the metal gasket/dam. Should I bite the bullet and replace the pump now anyway? It looks good, but if there is a problem I will replace it. Thanks guys....