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what is the bolt on the head just above the vacuum pump. Looks like a plug of some sort? I noticed it over the weekend looking at some engines?

That is the hub/mounting bolt for the timing chain guide sprocket inside the engine.

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Yes, an idler sprocket. Also the location of the SLS pump on 300TD models.

98a

Thanks for the info. Lonnng shot here...is an sls pump able to be mounted there on a non sls head or is there internals casted into the head that are different?

Completely different casting. There is no way to put an SLS pump on a non-300TD head.

darn!!! gotta find a way to fab an sls pump mounted externally or go with a w124 style pump

http://www.youtube.com/watch?v=yPFQiFuA_iI

check out the above video "This is a OM617.951 diesel engine from a W126-300SD running in a W123-300TD Turbodiesel. Because the engine has no self-levelling system pump, the previous owner connected the self-levelling system to the power-steering pump."

That will not work. Mineral oil is too thin for the power steering system and the power steering pressure is too low, thats why the W124 uses two pumps. His steering pump will die in short order, especially if he tries to haul anything in his wagon.