Mk1 Diesel Golf Welsh Plug Size

[saschw]

I'm getting ready to refit an engine to my MK1 diesel golf when I noticed one of the welsh plugs is corroded.

After removing the plug, I found the size I need seems to fall between 35mm and 38mm. Unfortunately, the workshop manuals I have don't specify the welsh plugs at all.

Does anyone know what size plugs I need? Hopefully, they are a standard plug? I've read elsewhere that there maybe a slight difference in size between the the petrol and diesel plugs?

Thanks - Shane.

[roccodingo]

36 mm . .