There's 2 connections there. Mine was leaking from the bottom, albeit slowly. I really only noticed when doing headlight lens. New oring fixed it although I did have to go to a hydraulic shop since my kit did not have the right size. Also on the topic of expansion tank, they certainly do crack and leak, you will find several posts on here about it. I thought mine had cracked at one point but it turned out to be oring on the bottom of the tank, so I would check that as well if you suspect the tank.


On the egr cooler, yours is different than mine, but I would say it could be either or if it's a descent amount you're losing, probably the 'ribbed' area. I believe that's where they crack and cause a larger leak. Not really sure as I removed mine a while ago.