rickybobdy riggodeaux thanks for quick replies, guy at garage put the New O - ring in the right place for sure, it goes in the groove basically where the old 'flattened' compressed ring was and oiled it also...the cap is in great condition to be honest....

I did a little test also, loosened the cap a little, drove for 10mins and result the same, then did another 10mins of driving and seemed to improve, not sure if engine temp related.Also when i say leak ,I don't mean the type of catastrophic leak you would get if you didn't put the o-ring in the groove of the filter, this is just enough to dampen your finger tip as you run it round the edge where the filter cover mates with the metal housing....I'll monitor attach pics if needed and like ricky bobby said will get a new filter if need be ......

PS it was a mann filter, and old filter needed a fair bit of tugging to remove as it was attached to cap, is this normal?
pss wife is going nuts, last weekend was the cv boot clip loose on x5 saga, and this weekend seeping o ring hmmmm

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