Hi,
1. Anyone knows what is the seal for on brake caliper pin (red circle on the picture)?

2. It should seal the air in the bushing or let the air off from the bushing? The seal seems to me is swelled up but it might be ok, I do not know. When I put a little grease on the pin, the pin is pushes out by the locked air up to 50%. Is it OK? Ican not push it fully in to the bushing.

Roman.

 

The seal is there to reduce and brake noise. If you greased it up, (good job!) the pin will try to push out as you install it. Normal. Just keep a little pressure on the pin as you install it being careful not to mistake the air lock for cross threading. It's not totally air tight so it will leak out and be fine.