VW Passat Heater Core Replacement

Ski season is approaching.  I need to get the heat working in the car.  At best it is luke warm.  The car is a VW Passat B6 and one of its weak points is the heater core, it gets clogged up over time... you know the "lifetime fill" thing.  Yea, the coolant is good until the lifetime of the radiator or heater core is over - cut short in the prime of the cars life because the coolant was never changed!  

VW recommends when you change the heater core, to flush the cooling system twice.  OK, not big deal - open the drain plug to let the nasty old coolant out.  You ask "Where is the coolant drain plug on a VW Passat B6?"  Good question - THERE IS NONE.  I looked for an hour - if you can find one, PLEASE post it to the blog.  I took off the front bumper looking for it per one video, I searched for an hour.  Ughh!  

So how to drain the coolant?  This article was helpful.  But since the is no drain cock on this car, I used the following method.  

Remove the passenger lower wheel well liner.  This allow access to the radiator hose.  (Don't confuse the radiator hose and the inter cooler hose.)  I removed the hose from the plastic fitting (not the quick connect coupling from the radiator.  I did not want to tug too hard on the plastic radiator parts or coupling shown on the right side and break anything.   

 With this hose disconnected I skipped to the step where the small hose is removed from the top of the coolant expansion tank and used compressed air.  

With two fill and flush cycles I was able to get the water coming out of the system to run clear.  

Now - on to the heater core replacement.  This video is a good representation of how it is done.  The factory heater core was marked as a Denso.  So I purchased the Denso and saved around $100 versus the VW branded one.

The Denso does not come with the plastic surrounds on the heater core. I used the old one.  

Much is written about removing the old core and getting the old core out.  I found it helps to simply cut the old HEATER CORE hard lines so I could then get a perch and twist and pull on the old pipes.  I used a Dremel oscillating saw, with this bit

I then lubricated the new o-rings with some silicone paste.  Installed the clamps (a real pain).  Work slow, and don't bend the tubes, they are really soft.  

Finally I pressure tested the system to make sure all was good.  The tool I used was not a traditional pressure tester - I don't have one.  So I used this instead.  Handy to have if you do frequent flushes.  

Follow-up:  So the heat was still not great unless I revved the motor like crazy.  Next suspect was the Auxiliary coolant pump p/n 1K0965561G .  

I removed the pump by clamping off the two hoses so as not to loose a bunch of coolant.  I then jumped the motor with 12 volts and the motor did not run.  So seems like the pump is bad.  

Update:  Pump replaced.  Easy job.  The Pierberg pump at FCP has the VW logo scratched off.  

Heat has improved.  Time to bolt on the Blizzacks, then I deem the Passat Wagon (the swag-wag) ready for ski season.  ;-)  But wait, there is more - 

(Follow up - - As mentioned VW Says flush to cooling system twice when you replace the heater core.  DO THIS!  I did not, since, I had changed the coolant a couple of times, and flushed the old heater core in each of the last two winters.  Bad mistake - on a ski trip 1000 miles from home the heat got weaker and weaker.  Trip to the dealer - new heater core and $1000 later I have great heat, and a very slightly used Denso heater core for sale on eBay.) 

Close (esc)

Flash Spring Sale

Flash Sale: Buy One , Get 50% off a second pair. Limited Time, Act NOW!

Shop Now

Age verification

By clicking enter you are verifying that you are old enough to consume alcohol.


Shopping Cart

Your cart is currently empty.
Shop now