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Discussion Starter #1
So guys I come to you in need of help, so I just discovered that my 05 H6 has a bit of a cooling issue. What i mean by this is if you let the car just sit and warm up it wont stop at operation temp it will creep up higher and higher despite the fans coming on. Here's the odd part though, the reason that its taken me so long to notice this is, if the car is moving and you're getting any sort of airflow you'll be 100% ok unless you want to go through a drive though. :mad: Im taking an IR gun/camera home from work today to look everything over to see what is going on. If you have any ideas let me know I would really appreciate it. And hopefully when I replace the thermostat tonight everything will be fixed, figures crossed.

~Garrett
 

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Typically this is due to a fouled up coolant flow. Subaru only tstat after market parts store tstats are known to be one cause of this. Mucked up radiator ie crud in the radiator restricting flow. Or radiators outside gummed up with yrs of bug carcases and simply not cooling well. Also both fans going on if the larger fan has failed this has been another source of temp increase while not moving.
 

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OBW H6 VDC, Tribeca, XT6
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No other issues - sounds, Check engine light, etc?
any recent work done?

1. Reduced coolant flow: Clogged radiator or tstat.

2. Headgasket. When it does it again - get out and look in the overflow tank for bubbles, could be just one every second or so given how light your symptoms are.
 

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Discussion Starter #5
ok so to give some more info what I know is that both fans are running and will ramp up to the max speed but it wont help. Secondly im going to take a look at the radiator with the ir camera tonight to see if any channels are clogged. As for headgasket I wouldnt imagine that it would be this as there is not odd smoke or anything due to the combustion mixed with coolant. Third I do have a Check Engine light on and its P0420 and it has to do with the bank 1 cat being below threshold.
 

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Coolant flow or heat shedding... Thats your issue, whats causing it is tbd.

When the car is moving both flow rate and cooling ability increase. When your not moving cooling via air flow is reduced and flow rate via water pump is lower. A really dirty plugged up outer core can do this from yrs of dead bugs packed into the cooling fins. Or some type of flow restriction internally.
 

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OBW H6 VDC, Tribeca, XT6
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indeed i hope it's not headgaskets, hopefully something simpler.

As for headgasket I wouldnt imagine that it would be this as there is not odd smoke or anything due to the combustion mixed with coolant.
these never smoke when the headgaskets fail. they will pass compression tests, no oil coolant mixing, and generally pass all the standard headgasket failure tests.

symptoms escalate like this, sometimes over the course of a year, with months between episodes:
1. overheating - often at idle/stopped
2. very random overheating
3. booling out overflow reservoir
4. bubbles in overflow when overheating occurs.
5. more random overheating happening while driving
6. overheating and when heat is turned on in the cabin the air is initially hot for a few seconds then cools down - no heat in the cabin while engine is overheating
7. after that issues escalate to common overheating, boiling out the overflow.

Third I do have a Check Engine light on and its P0420 and it has to do with the bank 1 cat being below threshold.
yeah that's not related to the overheating. in 2004 and earlier Subaru's it's only an indicator, the ECU doesn't even use it for anything. you can physically remove/cut the sensor and it won't (can't) change how the engine runs at all.
 

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WOW that is one sick radiator!

i drive a few miles of dusty gravely roads every single day and my 220,000 mile radiator doesn't look anything like that.

my Kubota diesel tractor radiator looks like that every year - are you using your Subaru like a tractor?
 

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Hahaha no not at all! My mom used it to commute to work for 8 years and then handed it down to me. We live in a pretty rural area but it's all 55mph highways, no dirt roads. It's probably been on a dirt road 5 times in its life. I'm just happy it was the radiator and not something more serious/expensive.
 

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Discussion Starter #11
ok so what im going to do is look for the coolant bubbling in the overflow after I replace the coolant then I'll do the heat test and ill take a long look at the rad. But my crazy idea was that there might be a bubble in the coolant jacket on the bank 1 side causing that side to over heat pre burning the hydro carbons before the cat, that through the code
 

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Riom given the age and its a h6, 99% your radiator looks like the one just posted. Raidiators are like $100. A bad one can wreck a $4000 engine, you following my logic?
 

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Discussion Starter #13
Riom given the age and its a h6, 99% your radiator looks like the one just posted. Raidiators are like $100. A bad one can wreck a $4000 engine, you following my logic?
yeah im going to take a peek at it now to see whats up, if the engines 4k i paid 100 bucks for the rest of the car lol
 

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Discussion Starter #14
UPDATE: So I looked at the rad and it was all clean like in the picture.
http://a.pomf.se/dwqhfv.jpg
As for it being a head gasket im going to check the heat symptom to see if it goes from hot to cold and to look to see if there is any bubbling as of right now my bet is on a water pump but im praying for the flush to work even though I highly doubt that itll do squat.
 

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2006 3.0r vdc
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Is that the radiator or the A/C condenser? My A/C condenser it just as clean as your picture and my radiator was absolutely clogged.
 

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Car: 2008 Tribeca, 2010 LGT, Sold: 2005 XT Limited
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Water pump on an H6 is no walk in the park. Whole timing cover needs to come off, then the chain.

Definitely replace thermostat.

Fans are 2 speed. Sounds like you are sure they are getting to top speed.
 

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Discussion Starter #18
Water pump on an H6 is no walk in the park. Whole timing cover needs to come off, then the chain.

Definitely replace thermostat.

Fans are 2 speed. Sounds like you are sure they are getting to top speed.
Yeah Im not going to be doing it alone my dads a mechanical engineer and hes been working on cars his whole life and wants me to learn just like he did.. the hard way. But ill make sure that its actually the radiator not the condenser. As for the fans im 100% that the came on low then went to full blast because i was standing by the car going between looking at the temp and the engine bay.
 

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From the glare on the pic it looks like you just took a pic through the front grille? If so you are looking at the condenser. The radiator is behind it. You can see a small section of the radiator if you look in the lower air intake (below main grille). You will notice that there is the condenser that covers the radiator almost entirely minus a couple inches on the bottom.
 

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Discussion Starter #20
From the glare on the pic it looks like you just took a pic through the front grille? If so you are looking at the condenser. The radiator is behind it. You can see a small section of the radiator if you look in the lower air intake (below main grille). You will notice that there is the condenser that covers the radiator almost entirely minus a couple inches on the bottom.
Yeah my bad but im back with good results. Just to recap the first time we simulated the issue we just let the car run at idle until it hit operating temp. from there the temp continued to rise with the fans coming on low then full blast to no avail (note the air that it blew out felt cool not hot as it should). But this time we put the front 2 wheels up on ramps, I looked at the coolant res there was no bubbling and then i cranked the heat all the way up and it blew hot without dropping in temp, so far so good right. After poking around for a bit the fans came on low and blew hot air out then shut off indicating that the engine was being properly cooled. After we shut the car off, I noticed that the coolant was low. We topped it off, my guess is that it was a air bubble that got filled by the coolant in the res.
 
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