Could be welded of only stripped to parts.. seals will burn. Spracer is simple ring turned on lather with notch for O ring to seal against block.
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Ex: 525tds 130kW, C250TD 160kW, E320CDI 200kW, ML400CDI 230kW, A6 R5TDI 130kW
Now: Q7 V8TDI 240kW, 320d 150kW, 335d 210kW