Again thanks to all the posters here, am edging towards thinking it is the stem valve, and only when it is in motion as one person said and the forces are greater on the tire, the washing liquid and spray i have had 3 garages do it, 2 pairs of eyes peering over it as it was being sprayed and rotated...and I also did it myself....

I have a tank large enough to dunk it, worse comes to worse will take it off myself and dunk it and see after pumping up slightly higher....

X has a habit waiting for the holiday season to throw up surprises, last year was the starter

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E53 X5 3.0d SUV prod.date 11/2004 eng.variant M57N Europe Right hand drive N