Low Heat/No Heat from heater and EGR Cooling faults

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sabres1016

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Jetta TDI MKVI

I am posting this as to maybe help another since the winter is coming soon. I had noticed last winter that my heat was very low. Basically to the point that it was cool coming from the center vents, but out of the side vents it was warmer. This is what was confusing me. I lived with it because it doesn't get that cold in North Texas and I have heated seats. So, when I replaced the timing belt and flushed the coolant (which had crap floating in the reservoir). I took the lines off of the heater core and ran water through it and I saw clean water and nothing obvious that showed the heater core to be clogged. Put everything back together with no help. During the spring time I started getting EGR COOLING faults and a MIL light (unsure of the fault code itself). I would clear the fault and it would go away for a month. The fault started becoming more frequent over time. From what I found, this is definitely a heater core issue because the coolant runs through the heater core before going to the EGR valve. IF the heater core is blocked, the flow will not be efficient enough for the valve. I replaced the heater core and have had no problems since. As a matter of fact, the heat is so damn hot I never put it on full heat. So anyone with a TDI that is having an EGR COOLING issue, take a look at the heater core. I also read that this is a common issue with the Volkswagens'. At the time I had between 120-130k miles when i replaced the heater core.
 
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Jef

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On the older Passat vehicles, 1999 to 2005 range, the heater cores would clog up. A good fix was to remove as much coolant from the heater core and then fill it up with CLR and let it soak for several hours, then flush it out. I wonder if the same would of helped your heater core?
 
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DrPeter

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Hi there,

Nice find, the Volkswagen Group does recommend replacing the coolant as per the maintenance schedule and to use the proper coolant for the vehicle!!
'Important: NOT ALL coolant types can be mixed as some of these coolants are NOT compatible.

See the table below:



Hope this helps,

drpeter
 
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Jonesy

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There's a little gel/powder bag (like a salt sachet) inside the coolant reservoir that can burst and contaminate the cooling system & block up the heater core rad.This usually happens when wrong coolant is mixed. Best practice is to replace coolant reservoir and heater core together and flush entire system a few times. Usually the reservoir goes dirty and black looking and hard to see the level of coolant without taking off the cap. It's double skinned so I find them very hard to get clear again.
 
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Jonesy

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Also the heater core itself is designed to allow coolant through even when it's blocked..... It's designed like a bypass system that will still allow the circuit complete even if the tiny cores are clogged up.
 
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