I did a search, read in both my manuals, and I still can't find - how much oil to put into the filter cup! the manual suggested there is a mark - there ain't no mark. the other manual suggested there should be some oil in the upper cup, so the level would have to be about an inch deep in the lower cup. These filters route the air down around the outer part of the filter to the cup, then up the inner part of the filter through the screen. My DD book shows the air coming in down a central tube to the cup, so these filters aren't the ones shown in the DD book.
I went ahead an put in oil to 1/4" higher than the ridge that the inner cup sits on. Is that about right?
Brian
Mine didn't have marks either.... I put too much in and it promptly oiled exterior my engine as soon as I ran it. You need to look at the situation. The oil should be high enough to be a source for the filters to wick up, but not so High as to overflow/get into the engine.
The fresh air comes from the outter section, goes thru the oil bath and is then pulled up thru the metal filters. At least in my MCI 8V71; same as a previous 6V71 (but with 3 filters instead of 4).
There is (should be) a baffle that sits in the oil cup. It's about 1.5-2.0" deep. There is an oil mark level on the cup, too. If I remember the level is a bit lower than the top of the baffle that sits in the resevoir cup. Over time the oil will get used/evaporated/etc, as it did in my bus-- it was bone dry, when purchased. Slight overfilled doesn't seem to be a problem, but the gaskets get old and might allow some leakage--RTV seal can be used.
I've either used ATF (first bus in '97) or a thinner engine oil, not straight 40wt (as the manual states). Used semi-synthetic 10-30 (left over for the BMW M3; please don't lable me... ::)) last time, that will flow well in cooler temperatures (Wisconsin) and allow cold weather starting. The idea is to lower the air restriction and promote smaller oil bubbles that will hopefully catch even more dust. I think DD recommended the same oil as the crankcase just for convenience; 30Wt in the 6V-71, for example. Overall, I always use a lighter oil, but think the colder it gets the more benefit there is.
Old filters can break down and it's a good idea to separate the layers and deeply inspect them. It seems some are made of spun aluminum, which is what I have and doesn't hold up all that well. I think my old GMC used spun stainless steel and were in excellent condition. Also, DO NOT use biodegradeable cleaner with the aluminum filters, if you plan to soak them over night-- it'll break the filter media down. When the engine is run, it'll ingest metal debris......let the imagination do the rest :o
Hope this helps some. BTW- a 4 filter system will take a case of oil (12 qts), but can't remember if it's enough for a "overfill" condition.
My 4104 manual says 3 quarts each so that sounds right for 4.