I'm trying to solve my lack of turbo kick and cleaned the banjo bolt and banjo fitting at the intake manifold over the weekend. They were clogged and definitely needed cleaning. When I did that same cleaning job on my 300D a decade ago, that restored my acceleration performance. It didn't work on the 300SD. However, I noticed that someone must have been in there before because only one washer was present on the intake manifold side. I don't know if that one washer missing could cause a small leak between the fitting and the bolt head, but that washer was there for a reason and I want to try that first before I move to other areas to check. I could go to the dealer and special order the exact washer for $3 and wait a few days for it arrive from the warehouse, but maybe I can use something off the shelf. The original washer is copper and the measurements are 11.5mm x 8mm x 1mm. Is it that critical than I get the exact size washer or can I get away with another size? Seems like as long as I'm close to the ID and OD, I'll be ok.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

It is not a critical area as there not much pressure. You could reheat the copper washer you have till red hot to soften it and reuse that and you can simply get some thick paper gasket material for the other side.
Note don't over tighten as some have stripped out that area or the previous owner had pulled the threads and the next owner competed the stripping.

Not sure what is in TX Ace Hardware out here has copper washers and steel washers with sort of a rubber O-ring built into them that gets crushed to seal.

if you degreased the manifold I think you could actually put a thin layer of Silicon Sealant around the hole let it set up for an hour and install and it should seal. You could to one of the alternative methods mentioned till you get the correct washer.

Harbor freight and I think Autozone have copper washer assortments. But I don't know if they have metric ones. On some occasions I have used the SAE copper washers and have opened up the hole on them so that they fit.

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84 300D, 82 Volvo 244Gl Diesel

If it's close and you can get a slight crush when you tighten it down, then you'll be good.

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1983 123.133 California
- GreaseCar Veg System

Part number for a 12 mm x 8 mm x 1 mm copper washer: 007603-008109. Site sponsor has them for less than dealer list price.

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Marshall Welch
Seattle, WA
1982 300D-T

Didn't need it after all. It was just stuck to either the bolt head or banjo fitting the whole while. Bypassed the switchover valve and replaced the primary and secondary filters as part of my testing and still ranging 17-18 seconds 0-60 time for a turbo OM617. Maybe it's normal aging, and I know one cylinder has lower compression than the others, but it seems like it shouldn't be that slow, even at almost 40 years old. Otherwise, it will run strong at 100+ mph. I'll be measuring boost to see if it's low and replacing the tank strainer at a later date.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.