Grab an old plug lead boot -Plug end - Straight type. Force this over the end of the dip stick & refit so that it becomes a seal & retainer. Its a harmonic thing that sets up in the dipstick and it just vibrates out at those RPM's. Just another lack of thought @ the design stage on fords part
, the
oil being flung of the timing chain is aimed straight at the dipstick tube and any crankcase pressure tends to carry it up the tube. If they had fitted the dipstick on the other side of the timing cover or in the pan like some other models it doesnt seem to happen.
Jac Mac