Technical

I recently replaced the chimney seal O ring on my A3 and it did not last long before steam leaked out of the chimney on heating up.

I replaced with a new pug and seal bought as a set and all is fine.

When I removed the plug before I changed it the O ring was left in the hole and seemed to have expanded or been squashed.

Thinking about what was happening I realised that it would be much better only to compress the O ring when needed ie when actually steaming the loco and when finished loosen the plug so the O ring is not permanently compressed.

This also is the case for the black O ring seals for the tender filler plug. The white neoprene type material seems much better on the tender seals. It was a poor tender black seal which started my investigation off in the first place as a black seal had been stretched by possibly over compressing and leaving compressed in storage.

When steaming is finished I now only loosely screw in both plugs making sure I do not compress the O ring seals. These must not be overtightened at any time.