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2004 Forester 5 speed
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130 Posts
Discussion Starter #1
I will preface this by saying that I had my 2004's thermostat and coolant replaced at the dealer in December. The stat gasket was leaking was the reason for replacement. I was smelling coolant at the time and was just thrilled it wasn't the head gasket.

1st of January 2010 [~2 weeks after the dealer service], I was driving [duh] about 70 miles into a 300 mile trip. I stop to get gas, and smell coolant. The expansion bottle is nearly full [this is not how it usually looks]. However the top hose is hot, and the bottom hose is cool, so I figure the radiator is working correctly, as is everything else. I am sure to check the temp gauge - which is normal - and everything is fine the rest of the trip. Bottle stays nearly full.

So I forget about it. I drive around town normally for three months without thinking of this and without problems. Never driving for any longer than an hour at a time, however.

Fast forward to this past Friday. 100 miles into 300 mile trip. I stop for gas and smell coolant. Expansion bottle has overflowed. Top radiator hose is hot. Bottom hose is cool. Temp gauge normal. I continue trip. I do not overheat.

The next day, after the car has cooled overnight, the overflow bottle has recessed back to the LOW line on it. The radiator is full. I fill the bottle back up to the full line.

NOTE: I recall while driving around in the 3-month interim that the bottle was typically more or less at the full line. However, I did have an oil change last week [before the most recent trip] and the lube guy might have over-topped off the overflow bottle. I did not check it since the oil change.

I start the same trip back [300 miles]. I make it without issue. It looks like the expansion bottle overflowed some, but not a whole lot. I will check again in the morning after it has cooled.

When the expansion bottle was full, it wasn't like it was boiling over. I overheated about 40k miles ago [head gaskets and clogged radiator] and it was steaming. This wasn't the case. It almost felt like normal expansion, but it seemed to be expanding "too much."

The car hasn't overheated since having the stat replaced. Can anyone suggest what might be the problem, or even if there is a problem? I would rather not go to the dealer, since it is an hour drive away. No check engine light has come on, and no temp gauge spike. Also, the car doesn't feel like it is overheating. No way would I have actually completed my trips if the car was really overheating.

If anyone needs any more information, please let me know, and I will check.
 

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Premium Member
2019 Crosstrek 2018 XT
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14,503 Posts
Sounds like H. But if you didn't replace it with a Subaru Thermostat I would try that. Also test the stat before putting it in. Oops sounds like you have a Subaru thermostat. I'd replace it anyway. Make sure the fans are operating.
 

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03X MT
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846 Posts
The expansion bottle at the low mark when cool is the way it is supposed to be. Do not add coolant to the full mark when cool. Where is the coolant supposed to go as the coolant in the radiator expands? it will blow out the top of the bottle.
 

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01 Forester S
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102 Posts
All too often, techs will install a 'spec' thermostat. These usually do -not- have the toggle in them that original Subaru thermostats do. We always use either original Subaru or Mishimoto (lower temp) thermostats. My personal pref is the latter. Easy (messy, but easy) to check and replace.
 

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2004 Forester 5 speed
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130 Posts
Discussion Starter #5
It was a Subaru stat.

So, when the coolant is at the bottom line on the expansion bottle [the one marked LOW], that is where it should be when cool? That makes some sense to me and would seem to allow PLENTY of expansion.

Adc, did you mean to say sounds like head gaskets?
 

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2014 Impreza Ltd CVT
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3,319 Posts
When is cools down, open the radiator cap, is there 'air' in the radiator?
If there is, I would suspect the headgaskets. ( rare to fail this way on an 04, but it is possible )

If the radiator is full of fluid, then it is fluid expansion, more than normal. And with the lower hose cool, I would suspect the recently replaced thermostat. Either failed ( not opening ), installed backward ( have seen this a few times ), or OEM NOT Subaru ( I have seen dealers invoice for a Subaru part when they got it from a local parts supplier ).

In any case, it would be best to drain the coolant, remove the thermostat and inspect to see if it's installed in the right direction, or that it has a LONG spring base as the Subaru part has to sit deeper in the coolant and open sooner.
 

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2004 Forester 5 speed
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130 Posts
Discussion Starter #7
Just went out this morning to drive it. Expansion bottle was still full, radiator wasn't full.

I dropped off my son [10 mile drive], and the temp stayed normal. Got home, popped the hood, and looked in the expansion bottle: bubbles.

So...I had the head gaskets replaced at 100k miles and I just hit 139k right now. Seems unlikely for an 04. Oh well. Going back to Subaru today. Anyone want to commiserate with me?
 

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2003 2.5x
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645 Posts
Ugh, I just hate reading stuff like this. It plain sucks to see so many HG failures, especially the repeated failures after initial repair.

I find myself checking ours regularly for tell-tale symptoms and signs, which can get unnerving...and we dont even drive it daily. Actually considering a rental vehicle for our upcoming vacation to DisneyLand. Wait... I thought we bought these for trouble free ownership:shake:

Damn Subaru, how could you get so many things right but this one thing sooo very wrong?:crazy:
 

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Ah crap.. I'm back with my 05 XS
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8,294 Posts
Sounds like my story. My coolant overflowing out of the overflow bottle first happened at 41k. Stat housing and/or gasket leaking since then too. Changed the cap and redid the coolant and it stayed normal. 55k changed the coolant again, housing/gasket still leaking, tightened that sucker down. Fast foward to 66k, I'm fixing head gaskets. Foaming of coolant, though not brown at all, and housing/gasket leaking like a mofo + a lot more oil seeping out of the HGs than I've ever seen before. I have an 05 with the xxx632 gasket.
 

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04 Forester X, MT
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1,039 Posts
I have owned (2) 2000 and a 2004 now. I typically have coolant bottle at "Full" mark cold. I have towed a 2000lb camper in summertime with 5 people and luggage and not blown coolant from the bottle, although I have seen it get maybe 1 to 1/2 inch from the top. This is at elevations generally below say 5,000 feet or so.

Just got the Subaru multi-layer-shim headgasket at 86kmi due to external oil leak. Hope it lasts!
 

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2004 Forester 5 speed
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130 Posts
Discussion Starter #12
Just dropped off the car at the dealer. The problem was a cracked thermostat housing - you know, that plastic thing??? This was letting air into the system, which forced the coolant out of the cooling system and into the overflow. Let's hope this fixes it! I was relieved to hear it wasn't head gaskets, which look good.

Can anyone tell me if a cracked stat housing would cause all of the symptoms that I listed?
 

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2004 Forester 5 speed
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130 Posts
Discussion Starter #14
Me too.

Does the cracked housing seem like a reasonable explanation?

They had to order the part; the cracked housing was made from plastic. Does anyone know if the replacement is made of something else? Pref. not plastic??
 

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Ah crap.. I'm back with my 05 XS
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8,294 Posts
Just dropped off the car at the dealer. The problem was a cracked thermostat housing - you know, that plastic thing??? This was letting air into the system, which forced the coolant out of the cooling system and into the overflow. Let's hope this fixes it! I was relieved to hear it wasn't head gaskets, which look good.

Can anyone tell me if a cracked stat housing would cause all of the symptoms that I listed?
Yes it would. For me, it just coincided with leaking HGs. But that plastic crap they use for the t-stat housing should be replaced with the replacement metal one as soon as you can. I got a replacement metal one.
 

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04 Forester X, MT
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1,039 Posts
Yes it would. For me, it just coincided with leaking HGs. But that plastic crap they use for the t-stat housing should be replaced with the replacement metal one as soon as you can. I got a replacement metal one.
is your replacement metal one aftermarket or perhaps one of the subaru "performance" parts?!
 

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Ah crap.. I'm back with my 05 XS
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8,294 Posts
nope, ordered the PN listed for my car from a former vendor here and it was metal, to my surprise. guess they finally understood that plastic sucks for the coolant system.
 
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