What, do you think, is the one way valve for on the w.w.. Is it to stop the water being sucked out when driving.The reason I ask is that the washers don't have "super car" power unless I bypass the valve. Will it let the water leak out when driving if I leave it out?. I can't test it myself as I have
removed the container at the moment for re-plating the blanking plates and reservoir retainers

 

The non-return valve is there to stop the water running back to the tank, and thus in theory preventing a short delay until the wash hits the screen. Total waste of time, and, as you say, mostly it stops the water completely! So remove and be happy.

 

I recently replaced both washer motors and wired them together so one for each of the jets, I fitted power wash years ago with the reservoir under the r.h.f splash panel and relocated the vacuum reservoir to the l.h side, straight fit to existing brackets, so I could try and improve the w.w. power but it disappointingly made no to difference to performance, The power wash on the headlight work, with extended wiring, as the old ones did, but I have never had cause to work them as I don't drive at night anymore.

 

I had similar problems Rex. In the end I wired and plumbed up a pump for a headlight blaster-jet type washer system, and that fixed it once and for all.

 

This was "related thread" on another post. Although there is validity to the shorter duration for fluid to spray, the one-way check valves are actually to hold the fluid in the lines over the hot engine and therefore have "heated washers" as advertised by Jaguar.

 

I do not believe they are on an XJS, as on my car the tubes are not (OEM) over the engine. Heated washers were electrically heated items, like heated mirrors and rear screen.

 

Hi all,

My one-way washer valve became clogged and stopped the washers dead. Cleaned it out with a combination of bicycle pump and garden hose. All now fine so it seems an easy fix if you want to keep the car original.

Cheers,
LeeP