Heater Core Failure

First time posting, just wanted to put out some info on my recent experience.
I just bought a 2014 Passat TDI SEL Premium, my first VW. Picked up the car last weekend and on the way home the CEL came on. Pulled the code and found P2457 - EGR Cooler Efficiency Below Threshold. After a bunch of research I was confident it was the heater core since there was no heat as well. Since it had the Extended EGR warranty I took it to the local VW dealer and they confirmed it was in fact the heater core. They flushed the system 5 times and replaced the heater core, all covered under warranty! Great experience with the dealer and very pleased overall.

Dealer also pulled code P040C in case anyone is interested. They mentioned the system was pretty gunked up.
Service ticket showed they performed Tech Service Bulletin #2040580 which appears to be this one.
https://static.nhtsa.gov/odi/tsbs/2016/MC-10106581-9340.pdf

I have the same car and had the same issue. I did not have a good time with my dealer. They did a replacement but put a leaking heater core in, got coolent on the interior, returned and my car, spent six more days in the shop. The service guy told me that this is a very common issue with this year. I have 76K on my car and it's had three heater cores replaced in that time. And this is my first WV too, I traded a 25 year old Volvo in on this car, wish I would have bought another Volvo.

I too had this problem after putting about 20,000 miles on my 2014; only had about 24,000 when I bought it. We had a wicked cold snap here in the south where it was like 55 degrees and noticed heat wasn't working then CEL came on. Figured I was going to be out about $700 for a new heater core only to find out it was covered under my "TDi warranty". We'll see if they actually fix it satisfactorily.

Pretty much every 2013 and 2014 Passat TDI seems to need a heater core eventually.

Some people report needing this repair more than once. What I cannot figure out is why; why would the system clog again with a new heater core and complete flushing of the cooling system and new coolant. I have seen some speculation that G13 coolant is the cause. Is that true? Should G12++ be used instead after a heater core failure?

The cause is a chemical reaction between the flux of the heater core and the g13 coolant. It’s impossible to get every bit of coolant out and replaced. Mine has been done twice at 41,000 miles (dec 15), then at 53,000 (oct 17). The car was parked most of 2016 and 2017. Still good at 87000.