One of the items that may present a irritating oil seepage on the 404 is that of the oil filter canister. Upper O-ring gaskets notwithstanding, more often there is an ever-present drop or two at the hex head bolt that secures the filter canister to the housing cover. There are a couple of reasons for this. One is the metal sealing ring (copper or aluminum) between the bolt and canister recess. Often the mating surfaces have become compromised by over tightening, scoring, or wear. If these visible items have been corrected in theory your canister should not seep. If however the seepage is still present, it could possibly be due to a non-functional inner gasket ! These are not so evident, yet can be easily serviced and replaced if needed. They sit in a small inner recess between the canister floor and the metal cap which houses it. They fail due to heat brittleness and aging, or perhaps by chafing when replacing the housing bolt after an oil change. Either way, it will allow oil to slowly migrate down from the canister and around the sealing washer under the bolt head. When tightening the bolt, should a leak or seepage result or persist, this inner gasket should be suspected and attended to in addition to the bolt, canister recess, and outer seal.
Unlike the standard OEM filter kit commercially available which does not include this part, our kits do ! Below you’ll see what to look for and how to go about a corrective fix. Part numbers where indicated refer to parts numbers found in our Catalog Nr. 4.
Pictured is a new canister showing metal seal ring recess. Does yours look like this ?
View looking down into the filter canister. Filter seat gasket seals the filter element via simple compression pressure. This gasket too may show signs of age and brittleness. Cap houses the inner seal ring. Remove the cap either by tension from above in a round-about fashion, or by pressure from underneath, similar to the removal of a bearing with the round-and-round motion from its seat. Caution should be exercised as the cap is rather fragile by comparison to the canister housing. Should any deformation of the cap occur, it may be straightened with a few hammer blows with a socket or metal sleeve of the proper diameter.
View of the canister base with cap removed. Reinstallation is straightforward with moderate pressure to seat the filter gasket, cap and seal ring.
Care should be used in removing the cap, as this item doesn't show up in the DB system. It does come with the complete filter canister assembly, but not as an indiviaula part as far as we know. See Catalog Nr. 4, Group 01-07-065S for our oil filter change kit contents.