For your question on the vacuum diagram, I would suggest that you use the search function button on this page. Type in 'vacuum diagram' and you will get about three pages of threads. Believe that one of those has several pictures of the routing diagrams. On the one about the oil cooler, it only opens up after the oil reaches a certain temp. So, until the oil gets to the right temp, there is essentially no flow thru the cooler. Can't say what % goes thru after the valve opens but it is probably progressive!?!

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150