Hi mate.
I don't know as I didn't open the boot to look, but I expect it was the cap venting.
This is what I found when I got home from the most useless radiator shop in Australia. Im impressed that the cap was holding.
I told them I wanted the PRT replaced but they weren't interested in doing it.
I'll order two from Brisbane and do it myself.
Ken
Sent from my iPad using Tapatalk HD