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2008 Subaru Outback PZEV,2010 Impreza 2.5i
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Discussion Starter #1
Dear All,

I have a new issue on my 2008 Outback base model with EJ 2.5 engine and 5MT.

There is no heat from passenger side vents including the passenger side center vent. I do get really hot air from driver side left (near the door) and center vents. When I run A/C cold air blows from all vents. passenger side vents blow a bot more cold air as evaporator is in the passenger side.

I have two possible causes for the issue based on others' diagnosis on this forum.

(1) Blocked heater core: This is a possibility as I have never flushed heater core before. I did, however, drain and refill the radiator every 30K miles and used only OEM coolant with coolant conditioner.
(2) Malfunctioned vent door. This could be a possibility as well, as I had an issue with air bag replacement. The dealer broke my dash panel and when I received the car back, I had no heat and no hazard lights working. I did get most of these fixed with a new dash panel, but, not everything back to the way they were before air bag replacement.

Based on above, I wonder where to start from. Looking at vent motors first? Or should I flush the heater core first. I do get really hot air from driver side.

Thanks
 

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I haven't worked on the heater duct system, but my understanding of the control vanes in the manual HVAC is that they're common to both sides; i.e., there's nothing that distinguishes how the air flows out the left and right side vents. If the air flow, i.e., where it comes out (whether cold or hot), is changing properly on both sides (face level, floor level, windshield), then I doubt the mode (air flow) control motors is a factor. Also, if the air temperature on the driver side also varies appropriately with the temperature control, then the single vane that directs air through the core to control the temperature is working.

Nevertheless, when the mode is set to direct the air to the floor outlets (and closing off the mid-level vents nearest to the doors using their rotary controls), is there the same sharp difference in air temperature between left and right? If not, then, again based on my understanding of the layout, the heater core is more of a suspect.

There's been a number of posts here recently where flushing the core has improved if not corrected the left-right heat balance in the manual HVAC system, and that's probably simpler to do first than taking the dash apart to access the mechanisms.
 

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2008 Subaru Outback PZEV,2010 Impreza 2.5i
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Discussion Starter #3
Heater core flush

Thanks Plain OM,

Yes, heater core flushing is more convenient than taking dash or radio apart.

Let me flush the heater core with a garden hose and refill the system either using distilled water or Subaru coolant and report results.
 

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2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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moved to gen3 section. where there are lots of other ones like this. (with differences in plain and auto climate control).
 

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2005 Legacy GT wagon 5MT Limited
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The scale always builds up on the passenger side, thus the symptoms that would seem to indicate a passenger blend door.
Thorough flushing sometimes helps, but replacing the core is the only fully effective solution.
Using the proper coolant is the prevention. Mixing auto parts store coolant with the Subaru coolant creates precipitates.
 

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2007 Outback 2.5i
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The scale always builds up on the passenger side, thus the symptoms that would seem to indicate a passenger blend door.
Thorough flushing sometimes helps, but replacing the core is the only fully effective solution.
Using the proper coolant is the prevention. Mixing auto parts store coolant with the Subaru coolant creates precipitates.
We've had the same problem over the years with our '07 2.5i. It's been serviced only by Subaru dealers since new, so I assume they used the proper coolant. Flushing the core helps (but not completely), but the problem always seemed to come back eventually. Traded it in this summer, so that'll take care of the problem for us. :smile2:
 

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2008 Subaru Outback PZEV,2010 Impreza 2.5i
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Discussion Starter #7
I never used auto parts store coolant but Subaru Long Life coolant. I did use Subaru coolant conditioner.
 

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2005 Outback Wagon 2.5 N/A EJ259 5MT
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I had the same issue. Flushing the heater core worked great. All you need is a 5/8" barbed end to female garden hose brass fitting, which will cost about $5 at your local hardware store. This will fit the OEM heater hoses in the engine compartment. Popped the short (~1'-2') heater hoses off the engine, flush water through each way, burp the cooling system, and top off with your choice of coolant. Or if you haven't changed the coolant for a while, flush the entire cooling system.
 

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2008 Subaru Outback PZEV,2010 Impreza 2.5i
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Discussion Starter #9
Thank you everyone for their response. I am very much inclined to flush the heater core with the garden hose. I have one concern through, The water supply here in Houston is hard. Thus, if I use hard water to flush the heater core, would the ions causing hardness corrode the heater core and especially cause issues with head gaskets? So far I only used distilled water and Subaru Long Life Coolant every 30K miles.

Compressed air flushing of the heater core is a better solution. I need to find a compressor and fittings to do that. Using a corrosion inhibitor in subsequent coolant is also a potential solution. I wonder if Subaru Long Life Coolant and conditioner has a corrosion inhibitor.

Thanks
 

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Use the garden hose because it's available. A few minutes of hard water exposure isn't going to hurt anything, just don't use it for the refill afterwards.

Every antifreeze on the market contains some kind of corrosion inhibitor.
 

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2008 Subaru Outback PZEV,2010 Impreza 2.5i
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Discussion Starter #11
Use the garden hose because it's available. A few minutes of hard water exposure isn't going to hurt anything, just don't use it for the refill afterwards.

Every antifreeze on the market contains some kind of corrosion inhibitor.
Thanks Rasterman. I will do a drain and refill a few times using distilled water to reduce/remove the water from garden hose afterward.
 

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Same problem on our 08 as well as the noises

The passenger side, center vent blows cold air regardless of the temperature setting. There is also a mysterious noise coming from that same area which at first sounded like the CD player trying to load a CD. I located a wonderful YouTube video that addresses the noise and it turns out to be the vent mode actuator.
If the heater core flushing doesn't make a difference (it didn't with ours) this might correct the issue for good. A lot of positive feedback.
Here is the YouTube link;

Good luck.
 

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I had the same issue. Flushing the heater core worked great. All you need is a 5/8" barbed end to female garden hose brass fitting, which will cost about $5 at your local hardware store. This will fit the OEM heater hoses in the engine compartment. Popped the short (~1'-2') heater hoses off the engine, flush water through each way, burp the cooling system, and top off with your choice of coolant. Or if you haven't changed the coolant for a while, flush the entire cooling system.
I'm having that same issue and did a heater core flush with no success. It still blows cold out of the passenger side while the driver side is hot. Help!!!
 

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2005 Outback 2.5i, Auto Transmission, 270k+
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Did you
I'm having that same issue and did a heater core flush with no success. It still blows cold out of the passenger side while the driver side is hot. Help!!!
Year, model, etc would help us figure out where to start.

There is a video right above your post that may or may not address your situation.
 

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Did you

Year, model, etc would help us figure out where to start.

There is a video right above your post that may or may not address your situation.
have you tried some CLR or neat vinegar and left over night ?? .. i had the same with my 06 and this sowrked for me .. left it in for 24 hrs and then give it a good flush
 

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My mechanic flushed it. Said it was super clean. The heat definitely comes out hotter now but it’s still contained to the driver side only. All the actuators looked like they’re working properly also.
 

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i would give it a good few flushes .. try it with the CLR over night and then the vinegar over night and see what crude that loosens up , took mine about 4 flushes to get the heat from passenger side decent
 

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i would give it a good few flushes .. try it with the CLR over night and then the vinegar over night and see what crude that loosens up , took mine about 4 flushes to get the heat from passenger side decent
have you tried some CLR or neat vinegar and left over night ?? .. i had the same with my 06 and this sowrked for me .. left it in for 24 hrs and then give it a good flush
Finally after three flushes I'm feeling some warm air. Problem is I'm not sure which worked better the white vinegar or the CLR. I think I'm going to try the vinegar tonight. I don't wanna harm it with to much CLR. Thanks for keeping me motovated!
 
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