We have the head off of my '93 320CE (M104 engine). While looking into the block cavities we noticed that the residual water in the cooling jacket around the rear cylinder area was rusty while the other cylinders was not. Did I have an air pocket back there? Is there no flow back there? Is there anywhere we can see a coolant flow diagram of this engine?
Anziani

Make SURE that your machine shop pressure tests the head. They sometimes crack between the water jacket and combustion chamber. They can be welded up and fixed permanently by a competent shop.

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Thanks Larry. Yes the shop is very good. The head is in good shape, just needing surfacing. After closely looking at the rust, it is very small particles. We think they just settled in that area of the block. I think I panicked needlessly.
Anziani