2014 TDI SEL Premium - No Heat

trentstafford

Member
Joined
Oct 10, 2019
Location
Illinois
TDI
2014 VW Passat TDI SEL Premium
I must admit that I did not expect to be posting here because I figured I 100% figured out the issue, guess not.

I recently purchased a 2014 Volkswagen Passat TDI SEL Premium in June, it has ran perfectly fine and no issues up until I went to use my heat. With the heat on full blast and the vehicle up to operating temperature I got no heat. However, if I would rev the car up while stopped or accelerated quickly, I would get a short burst of hot air, only for it to return back to being ice cold.

I consulted my friend who is a mechanic and he said that he is 99% certain that it is a clogged heater core, and after doing some research, it seemed like a pretty common issue. I ordered the part and spent what felt like an eternity installing it. Turning on the heat again I was met with ice cold air, no heat at all. I measured the temperature of both heater hoses coming in and out of the firewall and they were both at a decent 120-130. Coming into the cabin of the car, I felt the bottom pipe of the heater core, super hot, almost too hot to the touch. I felt the top one, ice cold, this is where I am stumped.

What I assume is that the issue lies in the blend door actuator, because it is near the lines on the interior which would explain the normal hoses in the engine bay and the one cold/hot one on the heater core itself. That's why I wanted to post here to see what everyone thought, i'm sure there are plenty of people here way more knowledgeable on these amazing cars than me.

Let me know what y'all think! Thanks in advance..:confused:
 

Herkypilot

Active member
Joined
Oct 28, 2005
Location
NC
TDI
'14 Passat TDI SE w/DSG
Resolved?

Surprised no one chimed in on this.

Did you figure out the problem?
 

93celicaconv

Veteran Member
Joined
May 22, 2013
Location
Wisconsin
TDI
Turned in my 2010 Jetta TDI Cup Edition to VW, DSG, Nav, Sunroof / Replaced with a 2015 Passat TDI SEL Premium
I'll try. I have a 2015 Passat TDI SEL Premium with the EA288 engine. You have the EA189 engine, so I'm pretty sure your cooling system is significantly different than mine. While I have a ton of 2015 technical references, I have little on 2014 and earlier models. But I'll share some thoughts.

Below is a coolant flow diagram for TDI's prior to 2015. Not sure this exactly pertains to your 2014 Passat. But, it should be close.

Now, in your model year and earlier, VW had a manufacturing problem with heat exchangers in the cooling system, where residual assembly flux was not flushed out prior to being installed. This flux, as it gradually mixed with the coolant (coolant is always slightly alkaline, with an ideal pH=9 or so), the flux turned the coolant gradually to slightly acidic (pH below 7.0). Well, the acidic coolant corrodes a lot of materials in the coolant passages. The pasty-flux and the debris from corrosion flow until they are blocked from flow in the smallest passages in the coolant flow circuit. That would be in the heater core, radiator, EGR cooling core, etc.

Now, if you were aware of this and monitored your coolant pH frequently, you would be wanting to flush and replace your coolant as your coolant reached about 7.5 to 8.0 on the pH scale (when at 7.0 pH, you are likely already too late). I did this soon after getting my 11,000 mile 2015 Passat - that coolant already was done to 7.5. The flushing gets most of the flux out (if it hasn't previously clogged a heat exchanger core). I was lucky and this preventative action hasn't caused me the problems you are now experiencing.

Now, if you look at the diagram attached, you will see the hot coolant coming from the engine first passes through your EGR cooler (6) before reaching your heater core (7). Regardless if your heater core was originally plugged or not, if your EGR core is blocked from this condition, you won't get much of any hot coolant flow going to your heater core. And, when you changed out your heater core, if you didn't chemically flush and then replace your coolant, you likely reclogged that new heater core with the amount of crud in your cooling system. Quite the cluster.

You stated in your problem statement that both inlet and outlet heater hoses were warm at 120 deg. If your thermostat is working properly, your hot side coolant should be at about 190 deg F, so your inlet hose temperature is too low.

Also, for the coolant to give up heat to the air from the heater core, the outlet hose temperature must be lower than your inlet. You said both were at the same temperature. Sort of feels you don't have any coolant flow to me. But then you said when you checked in the cabin of the car, you had a much warmer inlet and ice cold outlet. This is closer to normal. You can't hold a 190 deg F pipe in your hand, so it sounds like that temperature is near normal. The ice cold outlet suggest the coolant gave up all its heat possible, but the flow is so low that the coolant leaving slowly approached the temperature of the air going through the core. And because the coolant flow was so very low, the heat that was picked up by the air going through the heater core was so little, you barely noticed that it was ever so slightly warmer.

At any rate, debris in your coolant system (if with wasn't chemically flushed), not addressing your EGR core, and if you didn't change your coolant (only topped it off) the potential of the coolant no longer being alkaline likely have the EGR core clogged and potentially your newly replaced heater core, so you are back again now where you were when you first started.

Not good news, but I'm speculating this is what is going on.

 
Last edited:

Jmalibuss

Member
Joined
Jul 2, 2015
Location
LA Quinta
TDI
2013 Passat SEL
I am experiencing the same issue. Only getting 109 out of drivers side, progressively lowering to 75 it of the passenger side. I took some panels off to get to the heater core tubes under dash to take temps. The inlet and outlet temps are 160 and 130, I was expecting to see about 190 inlet. Also I was able to watch the blend doors move on both sides so I know they are working. Due to the above post about the EGR heat exchanger this is leading me to believe I may have the same issue. I was expecting to see a 190 inlet and much lower outlet from the heater core if it was partially plugged.

Any thoughts?
 

Tom in PT

Veteran Member
Joined
Jun 7, 2017
Location
Twilight Zone, WA State
TDI
2005 Passat sedan - SOLD; 2013 Passat DSG; both purchased new
Time to invoke the extended warranty on the heater core, if you are within the mileage limits. Check with a dealer.
 

brain_cow

New member
Joined
Dec 26, 2022
Location
San Antonio
TDI
2014 Passat TDI Sel Premium
@trentstafford

Sorry I'm late to the party... Sounds like your hoses were connected backward. Radiant heat would explain the 120F - 130F temps at the hose connectors. I'm guessing the upper house was 120F. You'd get a little heat when revving because it applied more pressure to the system, forcing it backward through the heater core.

Idk... That's just what made sense to me when I read your post. I'm not an expert.
 
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