Cleaning oil passages

[eyvind.spangen@c2i.net (Eyvind Spangen)]

I'm about to install a new head on my '87 Audi 100 turbodiesel, and I
thought about cleaning out the oil passages from the block to the
head. Can this be done without removing the oil pan and oil pump?
Should I clean the oil pickup tube, or will running really detergent
engine oil for 3k miles and then changing oil + filter  be good
enough? The previous owner changed the oil and filter every 4k miles,
but the car has been sitting for 6 months, and I guess there is a lot
of slugde in the oil pan now.. Anything to pour into the pan before
draining that can loosen things up a bit?

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Thanks,
ES