by John Scherrer » Wed Nov 09, 2022 8:23 pm
As this is a pressurised expansion tank (the blue cap is pressurised) and not an overflow tank, surely that upper pipe can't be vented to air?
I think it's an input pipe from the thermostat housing area. If the temperature gets too high and the water expands, it goes into the expansion tank via that hose. When the temps cool down, the water is draw back into the system by vacuum via the tank's bottom hose (which you cannot see in that photo)
Disclaimer - I don't have a '4' !
As this is a pressurised expansion tank (the blue cap is pressurised) and not an overflow tank, surely that upper pipe can't be vented to air?
I think it's an input pipe from the thermostat housing area. If the temperature gets too high and the water expands, it goes into the expansion tank via that hose. When the temps cool down, the water is draw back into the system by vacuum via the tank's bottom hose (which you cannot see in that photo)
Disclaimer - I don't have a '4' ! :(