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Discussion Starter #1
I have a 2007 Outback that my wife drives. to preface: She said she was not able to get heat to blow. She walked me through all of the stuff she did (basically turning the knobs numerous times in different configurations) and then at the end she said the heat started blowing and there was smoke blowing out of the vents too.

I drove car to work and found that:
1. the temp gauge didn't move for the first 2.5 miles of driving. Once it started moving it moved pretty quick up to the middle range of temp and then slowly crept higher.
2. If I park and leave the car for 5 minutes and then drive again it the temp gauge will lower as the car cools down but then creep upwards.
3. It got right to the lower line of the "danger" section of the gauge but I would pull over and let it cool down.
4. The coolant was low so I add and it didn't seem to make much of a difference.
5. Even when hot, it didn't blow warm/hot air.

I am thinking that I have a faulty thermostat. Before I begin troubleshooting, is there anything else I should be checking or thinking about? Heater core? Temp door cable?
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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If the overflow bottle was run dry (it was) then you have air in the coolant system and it needs to be bled out. This is step one. After the coolant system is properly bled of air, then further diagnostics can commence if necessary.
 

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Discussion Starter #3
Overflow bottle was not dry. It had coolant in it, just below the "low" mark by about 0.5"

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03 H6 OBW & 06 WRX Sportwagon
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while this issue continues, do not rely on the coolant level in the o'flow bottle, always check the radiator.

new quality radiator cap would be a good thing to try, the radiator 'should' have been maintaining proper level by pulling coolant from the o'flow thru the cap back into the radiator.

refill everything properly, check the rad's level and maintain the level in the overflow for 3-4 'drive cycles' . On my soobs, I didn't care for how stiff the o'flow tube was on the nipple at the rad's neck, so I used 2 small zipties to clamp it tight - just in case air was slipping past.
 

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1999 Legacy Outback, 2008 Outback
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if the thermostat is stuck open the heater would blow cool air...
jim
 

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As Traildog has suggested I would give it a good burping like a baby. When cold park it facing uphill take the rad cap off and let it run until it starts getting hot. Any air should be pushed out. Then put a new original rad cap on.
 
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1999 Legacy Outback, 2008 Outback
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But if stuck open wouldn't engine temp run cool?

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or it could be broken? i had one that was broken in half
when i removed it and yes, the car was overheating. cheap
thing to replace. another big possibility is the dreaded head
gasket fail. i've had two fail in the last 5 years and the last
one even passed all the tests, and it was still the HG. they
can be very difficult to diagnose...
good luck, jim
 

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I am thinking that I have a faulty thermostat.
Nah, forget that. That's not it and if it is it's an easy fix and proper diagnosis will get you there anyway.

Before I begin troubleshooting, is there anything else I should be checking or thinking about?
Yes you should diagnosis this properly.

Overflow bottle was not dry.
The overflow tank isn't really worthy of diagnostic data.

1. properly fill and burp the radiator, just filling the overflow tank is pointless (as you have already found out)

Your goal is to determine if:

After properly filling the system (via radiator) then you'll want to keep a close eye on coolant loss.

a. is it loosing coolant?
b. is it loosing with no signs of coolant (internally)?
c. is it loosing via boiling and overflowing out the overflow tank?
D. is it an external leak somewhere?
E. is it still overheating - and when?
F. if **a properly filled and working** system starts to overheat - check the overflow tnak immediately and look for signs of bubbles in the overflow tank or boiling in the overflow tank.

You don't want to confuse a boiling overflow tank/fluid loss with external leaking.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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If this was the case...

Overflow bottle was not dry. It had coolant in it, just below the "low" mark by about 0.5"
I assumed based on this ...

4. The coolant was low so I add and it didn't seem to make much of a difference.
However, now I confused by it ...

while this issue continues, do not rely on the coolant level in the o'flow bottle, always check the radiator.
The comments about no heat from the HVAC system , but blowing smoke right at the end, is a classic symptom of air trapped in the heater core. Things try to get hot, they even smell of something burnt. But you don't get heat, just burnt smell.

The system really needs to be bled of air. The proper way to do this is to jam a large capacity funnel into the highest point of the system. (The rad cap in this case) The coolant heats and expands (and burps) into the funnel. During the process you need to cycle the heater and the A/C. And you need to bring the car to operating temps. You will know when the t-stat opens. It's will be dramatic. You may need to empty some coolant from the funnel. Eventually when bled, you have to let the coolant contact and cap it up (with a full overflow) As soon as the level reaches the bottom of the funnel.

Properly bleed the system as step 1.
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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@sternman318

@rsrocket1

I was going to suggest the proper. tool. I knew someone else would. Besides, I have to post my "where the is a *******, there is a way" method.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Front end up on jackstands seems to work well.
Lets you easily grab the lower hose to check the thermostat is open, too.
 

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Discussion Starter #16
Just burped the system without funnel. Not great way to do it but everything is closed in New Orleans today. Heat is working fine. Test drive and no overheating.


Question now is how does air get in a relatively closed system?

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03 H6 OBW & 06 WRX Sportwagon
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Just burped the system without funnel. Not great way to do it but everything is closed in New Orleans today. Heat is working fine. Test drive and no overheating.


Question now is how does air get in a relatively closed system?

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'gas' gets in;

if there is a spot that flashes to steam

if there is an internal head gasket breach, combustion gasses can get in.

if the overflow tank is empty when the system cools.

if there is a leaky seal of some type; radiator end tanks, rad cap, overflow tube, hose clamp, etc. - air can be sucked in when the system cools.
 

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Discussion Starter #18
Just spoke to Subaru mechanic. He said need to add Subaru cooling conditioner. It's imperative to keeping it running well


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@Subaruzi

Not imperative, but doesn't hurt. I believe Subaru was pushing it hard because of head gasket failures- this can help seal/ prolong life of head gasket in some cases. It's cheap enough to be a 'why not'.
 
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