A4 B7 2.0L TDi still not fixed

Me again! I wish there was better news, but I still have a cooling issue on my son's car. Changing out the water pump with no impeller has made things a lot better, obviously, but we still have an intermittent loss of coolant, mainly when the car is driven on the motorway. My son has noticed white smoke from the exhaust from time to time. I am thinking that we have a faulty EGR cooler. Having read up lots on these things, it sounds like it is a likely culprit. I have performed several cooling system pressure tests and it always holds pressure, but I have read that this is the case because the coolers only leak when they are very hot and under a lot of load. I was wondering, in order to test whether the cooler is the cause, could I bypass the water side of it by connecting the hoses together in some way, and if so, would it cause any damage giving the car a motorway run with the cooler water flow not connected? Finally, if I have to replace the cooler, is it a job we could tackle ourselves? Thanks, any replies will be gratefully received.

What is the VIN?

Hi Crasher, hope you are well. I can get the VIN when my son gets home in about an hour, but the reg. is ML08 UWY

Vin: Wauzzz8e68a134273