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2006 2.5i
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Discussion Starter #1
ive flushed my heater core 3 or four times now with improved heating from when i started. however after 5 minutes of full heat passenger side goes luke warm.

should i continue flushing it or call it and replace the heater core?

should i replace the evaporator and expansion valve while im in there?

anything else i should do while i take everything apart
 

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2005 OBXT Limited, VF37, STI intake, 5MT
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1,568 Posts
Is it just the passenger side that goes luke-warm?

Does your car have dual-zone temperature control? (Digital display with two temp knobs)
 

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2006 2.5i
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8 Posts
Discussion Starter #4
i apologize for the lack of information. 06 outback 2.5i Manuel heating, i wish this was just a simple dual zone actuator...


it does not have a Subaru thermostat, altho it does look similar to the thermo pictured on the right. either way i find extremely difficult to understand how a thermo could effect the heat transfer of a heater core.
 

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'18 OB 3.6R
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64 Posts
These particular heater cores are really easy to get air in it when you flush them, and very hard to get the air bubbles out.

Also on an '06 I think the entire dash has to come out to get to the heater core? If I'm remembering correctly...there's no way to slide it out from the bottom - so that's something to look forward to.
 

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2009 OB 2.5i 4EAT
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ive flushed my heater core 3 or four times now with improved heating from when i started. however after 5 minutes of full heat passenger side goes luke warm.

should i continue flushing it or call it and replace the heater core? . . .
How did you flush the core?

The photos in the thread that @sternman318 posted show the gunk in the bottom tank of the core. The bottom tank is connected to the lower metal tube coming through the firewall, which is the inlet side to the core. This implies that the heater core is upward flow which seems odd; nevertheless if your core has anything like that clog in it, it won't likely move if the flush is done in the same direction as the normal flow -- it would at least have to be reverse flow.

If you're prepared to replace the core, and if you only did forward and/or plain water flushing up to now, then there's nothing to lose by trying a more aggressive approach. The linked thread mentions using "all kinds of stuff" but no specifics. There are radiator flush chemicals that might be tried. If the flushing fluid is poured in through the upper metal tube (the outlet from the core), it should make its way down the narrow core tubes to the lower tank. If then left there for some time (instructions might have more on whether this is recommended) the chemicals might soften/loosen the clog. Then reverse flushing, so that any pieces can exit through the lower metal tube without having to go through the narrow core tubes, might restore sufficient flow.

I suspect that in the linked case, where the bottom tank was clogged, the green material was mostly at the far end of the tank, i.e., away from the inlet hose. This is also toward the right side of the car, which might well correspond to where most of the passenger side air flows through the core. If so, then during normal driving, the incoming hot water would be pushing the clog in the lower tank toward the right and, at the same time up against the inlets to the core tubes themselves. In your case, the fact that the heater seems to work for about five minutes then fail might be explained by the clog material expanding in the heat or moving from the bottom of the lower tank to the inlets of the narrow core tubes toward the right side of the core.

Just an idea . . .
 

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I could see upward flow perhaps helping to purge air out....


otherwise ????
I was wondering why the up-flow (if I had that correct). Didn't think of purging. Indeed! Air rises, and if it's in the upper tank it will be pushed/carried out the upper metal core tube and eventually to the upper radiator tank where it's expelled through the rad cap to the external reservoir. Way to go 1 Lucky Texan!
 

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2006 2.5i
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Discussion Starter #10
These particular heater cores are really easy to get air in it when you flush them, and very hard to get the air bubbles out.

Also on an '06 I think the entire dash has to come out to get to the heater core? If I'm remembering correctly...there's no way to slide it out from the bottom - so that's something to look forward to.
I discovered that replacing the thermostat! i filled the system with a old style burper, since then only vaccum fills.

thank you for this i hadnt come across it in my reading, im lean towards replacing the core

How did you flush the core?

The photos in the thread that @sternman318 posted show the gunk in the bottom tank of the core. The bottom tank is connected to the lower metal tube coming through the firewall, which is the inlet side to the core. This implies that the heater core is upward flow which seems odd; nevertheless if your core has anything like that clog in it, it won't likely move if the flush is done in the same direction as the normal flow -- it would at least have to be reverse flow.

If you're prepared to replace the core, and if you only did forward and/or plain water flushing up to now, then there's nothing to lose by trying a more aggressive approach. The linked thread mentions using "all kinds of stuff" but no specifics. There are radiator flush chemicals that might be tried. If the flushing fluid is poured in through the upper metal tube (the outlet from the core), it should make its way down the narrow core tubes to the lower tank. If then left there for some time (instructions might have more on whether this is recommended) the chemicals might soften/loosen the clog. Then reverse flushing, so that any pieces can exit through the lower metal tube without having to go through the narrow core tubes, might restore sufficient flow.

I suspect that in the linked case, where the bottom tank was clogged, the green material was mostly at the far end of the tank, i.e., away from the inlet hose. This is also toward the right side of the car, which might well correspond to where most of the passenger side air flows through the core. If so, then during normal driving, the incoming hot water would be pushing the clog in the lower tank toward the right and, at the same time up against the inlets to the core tubes themselves. In your case, the fact that the heater seems to work for about five minutes then fail might be explained by the clog material expanding in the heat or moving from the bottom of the lower tank to the inlets of the narrow core tubes toward the right side of the core.

Just an idea . . .
i have suspected this, or created this same scenario in my head. so far ive just flushed back an forth several time per flush with water from a hose, however i had such good flow i didnt think it was still clogged (first couple time i got so much crap out of it). i think this weekend im going to hit lowes for a garden pond pump some 3/8 hose and a big bucket of CLR. As you said what is the worst that could happen?

Ultimately tho, im think it'd be in my best interest for longevity to replaced the hear core and radiator in one swoop. possibly throw a genuine thermostat too, tho i may wait till i tackle the TB WP and related seals.
 

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2009 Outback 2.5L, automatic
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My 2009 Outback has had heater issues for a year now. A shop pronounced the control and cable OK and thought they got heat. I got heat for about 10 minutes by surprise the other day, then back to cold only. I am prepared to flush the core. Please guide me as to which nipple is IN and which is OUT and how to do the reverse flush to not get air into the system as I have read is a problem. Thanks and Happy New Year to all in the Forum.
 
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