FAV flow issues on 2006 R53 Mini Cooper S

[Hyper Blue JCW]

I've spent some time trawling around here and testing different things and cant figure this out.

I've installed a HFS-3 system in my 2006 Mini Cooper S, have tested and primed the system (I get flow from the 6mm hose when linking SYS), but I'm having trouble purging from the 4mm outlet once I attach the 6mm hose to the FAV.

I'm getting flow into the FAV when I rev the engine or jump SYS. I say this because when I remove the 6mm hose from the FAV water that has been under pressure sprays open releasing the hose), but no flow through the FAV seems to be happening. I have been doing these tests with the engine running and the hose taped to my windscreen.

After seeing another thread here I decided to try flip the FAV and run the flow in the incorrect direction - and doing that works. I get flow through the FAV, into the 4mm line and out a jet attached for testing.

This pic shows how my FAV has to be configured to get flow out of the 4mm line:


I am not using a flow restrictor for any of my testing.

Are there any tests or checks I could do before I consider replacing the FAV?