That plastic disk is the main oil filter, without it in there you have NO filtration at all as the oil that is supposed to go through the bypass is instead simply going straight back to the pan!

It's a tight fit, reguardless. My brother's 300D is a huge pain, with a Wix filter or with a Hengst. You must fit the housing up onto the holder and then screw the bolt up (or you will bend the canister, we had to get a new one for my brother's, it was bent).

There is some art to this -- I can get it on, my brother (who is much stronger) cannot. As I said, you must fit the canister up and THEN start the bolt, else it goes sideways. The spring is quite strong, as it acts, I believe, as a pressure relief for the bypass filter. There is NO room under there, either!

And yes, the Ford tractors (8N series, I believe) use the same filter. You can get one at any tractor supply place (use Wix, they are the best). You must use the large o-ring and not the flat seal, though, or they leak.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!