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Thread: Washer non return valve

  1. #1
    Senior Member jberks's Avatar
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    Washer non return valve

    The washers seem to be the Achilles heel of the XF. Having cleaned the filter, replaced the pump and broken the wiring I’d hoped that was it. Sadly not.
    this week I noticed it was struggling to wash the screen effectively. The drivers washers weren’t great and the passenger one dribbled innefectively every 2 to 3 activations. I had to keep presssing until the headlight washers fired.
    Did an an investigation today. Removed the wheel, liner and pump. The filter had some film on it but only 1/4. Cleaned it but it was fine. Checked the pump. Wondered if the non oem pump was dodgy but it was fine too. Loads of pressure.
    Pulled the pipe from the passengers bulkhead connector and it wasn’t impressive. More of a dribble and Certainly not enough to drive a jet effectively.
    After more messing around I’ve found 2 things.
    Theres a 4 mm plastic reducer in-line in the main 8mm feed pipe then a non return valve. The valve is a little restrictive to the drivers side as you’d expect but much more restrictive to the passengers side. I removed it and blew through it. The difference is very noticeable. 3-4 times more resistance.

    I can’t think why it would restrict one side more than the other (and there’s no markings to differentiate) so I’m going to assume the non return valve is faulty and get a replacement next week. At least it’s easily accessible through the brake fluid access panel so a 5 min job to swap.

    The reducer has me scratching my head though. Why bother feeeding from the pump on a high volume pipe only to restrict it? I think I’ve figured it out. The system uses conventional components. A convention system pushes a large volume of water through jets on the bonnet with enough pressure to hit the screen at speed. A lot of water per press. The jaguar system lays a film of water onto the wiper blades. If the same volume and pressure came out of wiper mounted jets, it would flood the screen and hamper visibility. Clever really.
    2012 XF 3.0D S Premium Luxury

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    Senior Member Poundy's Avatar
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    Clever when it's working properly

    I must admit that one of my pet hates is on a breezy day when the car in front's washer fluid is spraying over it's roof.
    Last edited by Poundy; 03-11-18 at 22:32.
    64 Plate RSport 3.0D All Black, Ceramic coated, self healing front car wrap, 19" alloys

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    Senior Member Cats_paws's Avatar
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    Jberks' car is one year older than mine so I'll let him lead the way sorting out the little niggles that appear as it gets older. Then I can follow his instructions on how to repair them.
    2013 XF 3.0D Premium Luxury stop/start Caviar red metallic

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    Quote Originally Posted by jberks View Post
    The reducer has me scratching my head though.
    I'd think it is being used like an Orifice plate in a process pipe. Most likely to restrict the flow to increase the pressure, or if it's only on one of the sides, to restrict the flow to that line so as not to starve the flow to the other.
    2011 XF S Portfolio Black on Black

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    Senior Member jberks's Avatar
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    Quote Originally Posted by Tyrrp View Post
    I'd think it is being used like an Orifice plate in a process pipe. Most likely to restrict the flow to increase the pressure, or if it's only on one of the sides, to restrict the flow to that line so as not to starve the flow to the other.
    That's what made it so odd. You have a 6mm (rough internal diameter) pipe that comes up from the pump with loads or flow and pressure behind it. Once it gets to the scuttle panel near the brake fluid reservoir, the pipe stops and you have the restrictor which has a 6mm inlet and outlet but is reduced down to and smaller (4mm) internal bore. Then back out to more 6mm rubber pipe for the remaining 2 inches or so to reach the non-return valve. This is a T piece that has a 6mm inlet and 2 4mm (or smaller) outlets which subsequently head off to feed the 2 jets. Hence whilst the pressure increases inside the reducer, it will fall again once it leaves, only now with a lower flow rate. As I say, I suspect it's to reduce the amount of water that exits the jets, otherwise they'd flood the screen or hit the blades and fire straight up over the roof. It's also been suggested that with too much water, the blade may skip at speed.

    I've ordered a new non-return valve. This is a little cheap plastic T piece gizmo with a bit of rubber at the top presumably to stop the water flowing back from the jets. Ebay sell similar items for £2.50 but of course none of the eBay ones have the right size ends. So I've ordered one from my local Jaguar dealer. A bargain at only £21!!
    Just as an experiment, I've also ordered (from eBay) a 6mm straight through connector (a more reasonable £1.25) which I plan to swap with the restrictor just to see what happens without any restriction. I'm thinking I've never been that thrilled with the water volume from the jets. It may simply be better with the new valve but if not, and assuming my experimental wide open connector goes too far and makes it fire fountains at the following traffic, I may try to remove a small amount of material from within the restrictor to tune it to a more satisfactory middle ground.
    2012 XF 3.0D S Premium Luxury

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    Actually the way you describe it now it could be to actually keep pressure back against the pump.
    2011 XF S Portfolio Black on Black

  10. #7
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    Quote Originally Posted by jberks View Post
    ......I've also ordered (from eBay) a 6mm straight through connector (a more reasonable £1.25) which I plan to swap with the restrictor just to see what happens without any restriction.
    Please keep us posted on your tests. I've never been very happy with the washers on the XF. I drilled an additional 1mm hole on the driver side wiper (think the XK's get this as standard) to increase flow rate directly to the screen, but it is still not really sufficient.

    I copied the modification posted by this chap - helps clear the lower portion of the screen on the driver's side:

    2014 XF 3.0D Portfolio / 2006 Kia Picanto 1.1LX

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  12. #8
    Senior Member jberks's Avatar
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    Update
    so picked up the part today. £21 ish but it came in a kit with the connectors and pipe work for the bulkhead too.

    Before I fitted it I did the same test as before. Blew through in the flow direction. On the old one it was fairly free flowing Towards one Jet but more resistant in the other. Couldn’t blow through the new one at all. Which was opposite to what I expected. Anyway, fitted it and the washers are like new. Lots of flow, good pressure on both sides. I haven’t even bothered with the connector I ordered.
    So I guess rather than just faulty the old one was worn out and in reality they shouldn’t be free flowing but build up pressure before opening.

    2012 XF 3.0D S Premium Luxury

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  14. #9
    Senior Member Poundy's Avatar
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    Good find JB I'm sure it will solve a few problems for other members
    64 Plate RSport 3.0D All Black, Ceramic coated, self healing front car wrap, 19" alloys

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