How to: Replacing 2012+ NMS Passat heater core

Penst8grad

Member
Joined
Nov 24, 2017
Location
Pa
TDI
2015 Passat TDI SEL
I pried the bottom one off but the top was turning into more tension than I felt comfortable. I said "uncle". Not happy that a 6mm bolt is going to cost a large chunk of change but I am more comfortable with that than alternative. Former ASE certified tech, but I know when it's time to throw in the towel.

Thank you everyone for the great thread that was very helpful despite my failure.
 

ret1614

Member
Joined
Mar 16, 2021
Location
Carson City
TDI
14 Passat CKRA, 05 Jetta BRM, 02 JSW ALH
Seems like I may be reviving an old thread, but I just finished doing the heater core dance myself. Got the dealer to knock a grand off the price of the car, so it’s a fortunate thing.
Anyways, three things.
The 6mm screw holds a plastic block that the through firewall pipes pass through. Molded in, 0 give, that screw has to come all the way out.
The o-rings on my old heater core were stuck to the through dash pipes, messed around for too long before I finally cut the pipes off the old heater core and yanked them out after I got the old core all the way out of the way.
Getting the new core all the way seated into the pipes was a painful experience. Finally got some hose clamps and slide jaw pliers to force them together. Used water based lube on the o-rings, petroleum could degrade them.
I did take a few pictures, but I’m not sure how to post them up. I’ll chuck them on IG if anyone is interested.
 
Last edited:

superdavis78

Member
Joined
Jul 31, 2021
Location
Corbin, KY
TDI
2015 VW Passat TDI SE
I’m having a hell of a time getting the top heater core connection to seat. Bottom one seated just fine. I don’t want to force too much because of the thin aluminum. Suggestions?
 

PLC Geek

Active member
Joined
Jan 24, 2017
Location
Murrieta, CA
TDI
2015 TDI SE 6MT
It was one of those small wooden shop brushes with the square shaft like this:

The stuff on the other side of the firewall was disconnected. I had to get back there before because the fitting broke:

It was much easier, in my opinion, to get the core changed with access to the fittings on other side of the firewall. With my son on the other side pushing on the fitting with a piece of 1x2, I put the handle end to the flange of the fitting and used a mallet to tap it home.
 

superdavis78

Member
Joined
Jul 31, 2021
Location
Corbin, KY
TDI
2015 VW Passat TDI SE
I’ve got the top hose in the firewall disconnected. I’ll disconnect the bottom hose and see if I can gently push the pipes. I have the bottom pipe seated and connected at the heater core. That top one is giving me tough go.
 

PLC Geek

Active member
Joined
Jan 24, 2017
Location
Murrieta, CA
TDI
2015 TDI SE 6MT
I’ve got the top hose in the firewall disconnected. I’ll disconnect the bottom hose and see if I can gently push the pipes. I have the bottom pipe seated and connected at the heater core. That top one is giving me tough go.

When I was trying to fully seat the o-rings by myself, I was trying to use both hands to push the heater core tube into the firewall tube. I could see the firewall tubes mounting flexing backwards. I did not have enough grip area or strength to hold both tubes and push them together from the heater core side. I fought them for like 20 minutes, cursing the entire time. I finally decided to get access to the firewall tubes from the other side. It only took me about 10 minutes to remove the stuff from the engine bay as I had been there before to replace that broken fitting. Once I had access to the other side I had my son help me. He used a short piece of 1x2 to provide backup pressure on the tube from the engine side, and I used the handle of the brush and a small mallet to seat the tubes. I angled the handle of the brush against the flange of the heater core tube. A couple of taps and it was seated fully. Took less than 5 minutes.
 

superdavis78

Member
Joined
Jul 31, 2021
Location
Corbin, KY
TDI
2015 VW Passat TDI SE
Still having issues getting the top pipe seated into the new heater core. The bottom pipe seats up fine. I am at a loss. I feel like I’ve tried everything, and still no luck. Anyone have any suggestions?
 

calimustang

Veteran Member
Joined
May 17, 2010
Location
Central FL
TDI
2011 JSW DSG (buyback, RIP), 2014 JSW TDI, 2015 Passat TDI, 2013 Jetta TDI.
thanks! mine failed last year, now the cold front just hit this weekend so it is kicking my arse to get this done. :)
 

Penst8grad

Member
Joined
Nov 24, 2017
Location
Pa
TDI
2015 Passat TDI SEL
Ours failed again. 2nd time in 8 months!

Dealer finally got my wife's car in. (Allegedly) replaced the heater core again and flushed system 2x. She had heat when she left. Next morning no heat again. She called back to ask about warranty from 1st replacement and was told it was Goodwill since she was 1400 miles over 12mo 12K warranty on last core.

I looked at it over the weekend and found a lot of air in the system and expansion tank overfilled. Obviously the hope was it would burp itself. Burped what I could and now have Luke warm heat.

The only thing stopping my 1st time was 6mm bolt at firewall. I'd love to know how people get to it. I could not.

Car goes back for AdBlue warning (nox sensor) next week. I dont want to spend more on this heating problem.
 

PLC Geek

Active member
Joined
Jan 24, 2017
Location
Murrieta, CA
TDI
2015 TDI SE 6MT
The only thing stopping my 1st time was 6mm bolt at firewall. I'd love to know how people get to it. I could not.
Remove this stuff to gain access to that bolt on the firewall:
 

dantes

New member
Joined
Aug 6, 2020
Location
Chicago
TDI
‘14 JSW & ‘15 Passat
2015 TDi, 50k miles….looks like I need to start replacing mines also as the VW doesn’t want to warrant this, I’m suggesting to everyone of us to complain to nhtsa.gov of this ongoing issues, it’s not safe to drive the car when the defrosting is not working.
 
Top