CactusCabby

What is the size of the o-ring of the engine block plug?

Planning on flushing my coolant system this weekend (unless its supposed to be "brown"). I've SFTA and read several threads advocating draining from both the rad and the engine block. The only part number I've stumbled across is 078 121 951 for the plug and 904 520 02 for the ring. Neither of these brings up any related parts with a <preferred search engine> search...

hubturn

The block plug o-ring is part number N-904-520-02 and it is not very expensive. I am looking directly at the package mine came in as I ordered two for my '95 Cab. Always like a backup. I did get one at a decent hardware store for the purpose of flushing the block but there was no guarantee that I was getting a high temperature rubber compound. That's why I paid the Audi price for the real thing. While you are doing this job, get some plastic tubing and fittings and back flush the heater core and radiator, if you have the time. You will also need some compressed air to blow the system out. Be ready to probe the hole the plug comes out of as it will be packed with crud and you will be wondering why no fluid is coming out. I also highly recommend getting a 8mm 9 inch long allen socket at NAPA for about $15. A shorter allen socket with an extension will most likely jam in the hole to access the plug. Guess how I know about that! Get the right antifreeze too.