junk@ur-tut.UUCP (Jan Vandenbrande) (03/27/86)
.... The purpose of this message is not to open up a discussion or flames about oilfilters again. This is just a report on the disection of a VW oilfilter. Yes, I went through the oily experience of opening an oilfilter. It was the regular V.A.G. oilfilter used by the majority of VW and several Audi (?) gas engines (diesels?). Besides the expected paper(?) filter element, and a few other items to keep the unit centered, I found not one but TWO valves. Yes, TWO (2) valves. The first valve is at the very bottom of the filter, and leads me to believe that this is the bypass valve that'll keep the oil flowing when the filter element is clogged or the oil is too viscous to flow through the filter element (like in the morning after a -20C night). The second valve is at the very top of the filter outlet. This valve shuts off as soon as the oilpressure drops. So in a way it prevents the oil from flowing back the wrong way, perhaps taking the crud into the oilpan(?). The second function probably is to have some oil left in all the oil channels => Oil faster during start up, prevents corrosion in the oil channels. Now what's left is to disect a Fram filter. So I am waiting for a sale (I don't want to look like an oil monkey again). I'll keep you posted. (NB as far as I can see staring down other oilfilters is that they only have 1 valve [if at all], not two). Jan.