Hi all, just new here, had the l322 td6 for quite a while, since 2004

The water system gets pressurized, comes to temperature but the coolent in the reservoir stays completly cold. Changed the water pump, ...

Last time having it runing for an hour i stopped it and opened the reservoir, whilst opening it, heared it hissing and then the pipe on the webasto aux heater jumped off. water in the reservoir was cold...

I suspect some valve not opening, but cant see where in the system that could be,

Thanks so much for any council, so i can decide where to start looking