I know I've brought this up before- but this is a problem that will not go away !!

For the last 5 K miles, I've had sludge inside the dipstick tube- obviously water in there somewhere. I'm confused, however, because there is never any of it at the top of the motor at the filler cap (even when it is running) and the oil changes out clean. I've had the motor flushed 3 times now, and am seriously thinking about ripping the head off to see what the hell is going on. A friend keeps saying " don't pull the head, it's just condensation" but I have never had this problem before, and having just rebuilt the turbo, I'm a little concerened about that muck floating through the engine. Any comments as to what could be causing this ?

Thanks in advance