Has anyone ever cut open an oil seperator - breather box - to see what exactly it's made of, to help deduce how they can clog up and how to best clean them through? Is there a diaphram/filter or just channels to allow oil to pour back through return side?

I have recently been having some obvious crankcase pressure, with oil cap oil leak and rear main seal. Last checked the breather box had some 'chimney-like' effect when car was idling, so I assumed it was clear... all other PCV related hosing/nipples etc are clean.

So... what consitutes as a clear breather box, and was my deduction correct, or can I assume that partial clogging can be present causing some crankcase pressure? A few months back I did remove it, spray it down internally, nothing really came it, it blew very clean, but now I am not sure if maybe I should just replace it with a new one.

Note that in last weeks arctic weather of -45 degrees up here oil was fizzing out of oil cap... now in -25 no more, no major leaks. Could the EXTREME cold have solidified any oil sludge and caused this?

Advice anyone?

Thanks!
Greg Mustang
Montreal - Ottawa
Canada

I would change the oil breather box every 150k even if you can blow air through it. I changed mine at 220k and the oil leak around fill cap diminished 85%. The breather box didn't seem clogged when I got it off since I could blow air through it but it helped anyway to change it. I got a new one at the Volvo dealership for only $27 so I wasn't out of a lot of money.
Keith
--
1990 740GL Wagon 223k AW70L B230F 8 Valve Non-Turbo Rex/Regina

Kind of like a heart with an open chamber and a baffle or two. I have never seen one plug but they sure do get heavy with thick gunk that takes weeks to dissolve in parts cleaner. I think they could get occluded. But I think you can blow into the main hose to the box and feel the air coming out of the valve cover cap and conclude the system is open.

Great, but what I was wondering is if there was any significant difference between "open" and "open but restrictive"...
Is "open" enough to not cause oil leaks?

Greg

all the pcv boxes clog over time. only ones that don't have had synthetic oil since new. i like to change them at 100k as a maintenance item. they're cheap enough, just change it with the flame trap stuff and then you can forget about that causing the leaks. there is an oring that seals it to the block, they get hard as rocks and stop sealing. get 1 of them, too. good luck, chuck.