TOPIC:

After a lot of searching I have found an ideal replacement for the original radiator cap. The cap is a Gates RC 135 and costs 8 pounds through Ebay. The blow-off pressure is 16 pounds which is slightly higher than ideal but the fit is perfect. I think the 32 Euros being asked from a certain German site is taking the proverbial.

STANT #10229.
A cooling system pressure test confirmed it starts to open at 12 PSI.

That sealing rubber can be replaced, but I can't source it! Damn Home Depot or Lordco. Otherwise mine is perfect, just need a rubber sheet to cut a circle and install. There must local suppliers of different thickness rubber sheets! Or I have to go back to China to get something? Frustrating...

My OEM Rad-Cap had the same issue - The seals were starting to crack. I also looked at replacing just the rubber but the way the cap is assembled - essentially riveted - made this impratical and not worth the effort, given the modest cost of a new cap.