My left washer nozzle wouldn’t spray intermittently and then at all (US driver’s side/UK passenger side - same plumbing on both). After much cleaning, soaking, and blowing out of various bits, the one-way check valve or anti-siphon valve was bad.

I couldn’t find a Jaguar part except the full hose assembly, but Land Rover makes one that fits. It’s Land Rover part number AM6676. There are some differences, but it works fine. I ordered three because I have a sport wagon/estate (all sealed in original bags from dealer).

One of them came with the original smaller diameter outlets two of them were bigger but fit just fine. There are arrow markings on top of the originals to show the direction of flow, but they don’t appear on the new ones and the direction doesn’t seem to matter on any of them as far as I could tell.

While I was waiting for the parts I ordered. I drilled straight through the check valves internally. It worked as temporary bodge job but I found that quite annoying to live with. It would take several seconds and several dry wipes for the washers to build up pressure and then the initial squirt would be higher pressure and then the pressure would drop to a lower than normal pressure. It was a pain. The photo shows 1 larger diameter new LR part in the package and the 2 original Jag ones that were failing. I’m guessing there’s some kind of a rubber membrane inside them that can deteriorate with time &/or chemical exposure but that’s just a guess.

 

Plenty of parts on Temu site. Nozzles vary in quality, but don't buy the cheaper ones with shoddy plastic jets - ensure you get brass jets. Also, get the correct style - they vary from car type to car type. The check valves are slightly different, but the correct pipe diameter. Don't drill them out as water then siphons back to the tank and you have what you are experiencing. That is why there is an arrow showing flow direction on them. You can also get new rubber pipes and joiners very cheaply.