I've been meaning to make a further contribution to this thread and I hope the following helps in some way. I took the water pump of my car only to discover it was in perfect order. I had however ordered a new pump in anticipation of changing it for the original. Obviously I had an opportunity to take the original pump apart to discover the inner workings. I can tell you categorically the Jaguar pump only distinguishes itself from (at least some) others by virtue of a rubber seal that fits over/seals the electrical connections. This seal becomes compressed when the male part of the pump connection is pushed onto the female socket and presumably this helps assure a seal. In all other respects it is all but identical to just about every other pump I have seen. That's not to say there isn't a difference at one critical location and namely the pump seal. This is simply an o ring of sorts which sits in the housing just above the impeller as shown in “Pic 5” and “Pic 7”. In practice there may well be grades of seal better than others and just perhaps some seals are more compatible with screen wash than others. To be honest even with a failure of this seal I'd be very surprised that water can migrate past the previously mentioned electrical connection seal on the basis if water were to pass the impeller seal then it would come into direct contact with a dc motor and would surely cause a short circuit. Therefore I'm struggling to accept the diagnosis of water travelling via capillary action because in theory the moment it passes the seal the motor should cease to operate. Please see following the photographs to understand my conclusion.
BTW and as an aside the pump on my BMW failed shortly after I took the below pics. The pump was then 11 years old and was in a dire state but it was all but identical to the Jag pump bar the electrical seal as mentioned above. It appeared to have been leaking through the seal which incidentally was clearly degraded and I suspect minute amounts of water had passed promoting rust on the motor casing. I should also add the pump simply stopped working and given that water had come into contact with a dc motor then should I be surprised. I'm sure the same thing would and should happen with a Jag pump.
Now seeing the inner workings/construction of the pump I’m not quite sure how Jaguar can charge the price they do. In reality a £10 ( or less ) pump would perform just as well and from what I could make of it Vauxhall and some Fords use the same pump as Jag and supply it in exchange for peanuts. I can’t say whether these model include for the additional electrical seal which I should also say I believe is to stop water getting in rather than out. Seeing what I saw annoys me intensely when I know (as ever) Jaguar are shafting at every opportunity, I mean seriously £90 for a pump that cost them a fiver at the most!
Pic 1: The pump as removed from the car
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Pic 2: The pump electrical socket
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Pic 3: The rubber seal on the electical connections within the pump socket
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Pic 4: The pumps electrical connections
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Pic 5: The business end of the pump showing the impeller
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Pic 6: Another view of the innards
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Pic 7: The housing containg the pump seal situated above the impeller. This is the critical component
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Pic 8: Another view with the seal hosing removed
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Pic 9: The seal hosing with the critical component (rubber seal) all lubed with rubber grease and ready for re-install
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