We did make a few runs at the pod without serious problems and we even made it home without the ratling noise?????.
So today I contacted Nigel @ UKBlowers to give me some advise cause we where still a bit worried what it was. Nigel told us where to look, and this is what we found:

Should be caused by excessive local themperatures.............
Well it was pretty warm outside (saturday) and allready had a lot of citytraffic and traffic jams.
I already contacted Nigel whats next.