[xk] XK120 Windscreen Washer Plumbing


Am working on the dash for my XK120, S/N S677519 and wanted to get the windscreen washers to really work again. Replaced all the tubing. The old stuff simply crumbled when you breathed on it. Bit of a PITA to get all the hoses connected, but none-the-less, that’s done. The control valve on the dash was the next troublesome issue. Was able to find a new one at Barratt and had a question about plumbing it up. In Viart, page 320, it describes the washers. The control valve is identified as P/N C.5472/7. Amazingly, that is the same P/N that Barratt had on their computer. The valve is supposed to make a tight vacuum seal unless you push in the button, in which case, the intake manifold vacuum is supposed to suck the pump diaphragm up. Then when you release the valve, the pump is supposed to squirt fluid onto the windscreen.

My question is about the plumbing. In Viart, they show the valve with two fitting and the whole thing looks like a “T” with one fitting on the straight run and one on the branch. There is more detail if you google bobine jaguar xk windscreen washers detail. My question is about the plumbing connections. In my car, the intake manifold is connected to the straight run of the control valve and the branch goes to the pump. Viart shows it the other way. When I tested the valve, it made a tight shutoff with vacuum applied to the run fitting, but not on the branch, leading me to think the plumbing on the car was run correctly. Just wanted to check since Viart is a really good reference and it differs from the car and from how the valve seems to work.

Thanks Much,


In reply to a message from Clifford sent Wed 9 Mar 2016:


I looked at a spare C.5472/7 control valve. You are right.
Viart shows the rubber tubing routed to the incorrect
ports on the control valve.–
Mike Balch
Iowa, United States
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In reply to a message from Mike Balch sent Wed 9 Mar 2016:

I have one which is different from the one Viart shows on
page 320 but is exactly like Urs Schmid Volume 2 page 41.

The straight inline hose port is closed to the world unless
the button is pushed. The 90 degree angle port is open to a
small bleed hole in the side and also somewhat through the
shaft to the push button. When the button is pushed the two
hose ports are of course connected and there is a bleed
through the small bleed hole and the shaft. Thus there is a
slight vacuum loss when using the valve.

So you are right and Viart is wrong, unless he had a
different valve. He must have had a reason for drawing the
one he did. Could it be a later version from a 140 or
something? I think he did the 140 book first. I noticed he
has a 140 map drawer support.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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