After replacing most of my coolant hoses, a leaking overflow tank and the water pump I still had a leak. Actually a flood coming from the tank's new cap. I did not like how it closed so I replaced it with the old cap from the original expansion tank. It is a Motorcraft cap and screwed on like I expected. After a few trips around town the coolant level seems to have found a new normal and I now have no more drops. The "new" cap that came with the tank does not tighten properly on either the original tank or the second replacement tank I purchased 2 years ago either. On my son's Taurus, the forum's users really push for the use of Motorcraft parts like gas caps, radiator caps and ignition coils. I must confess that I always felt that was not necessary. However perhaps the "original" cap is better suited to control the pressure in the Jaguar system. Both of the caps that came with my 2 replacement tanks have no name on them and the center s different as well. The Motorcraft cap has a metal center whereas the others are plastic. Also the stickers on the replacement parts don't stay on either. My newest tank is hardly 2 weeks old and already the stickers are gone.From now on I will only buy Jaguar (Ford?) parts. Of course I already purchased a radiator so here's hoping iit lasts.