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2001 Subaru Outback Wagon 2.5 5MT
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51 Posts
Discussion Starter · #1 ·
My 01 2.5L OBW overheats (actually comes close to red but never goes over) whenever I drive for more than a few minutes over 50MPH. I can drive below that as hard as I want (flooring, redlining, A/C blasting) and it won't go above mid.

Head gasket? Did a block test and no combustion gasses in coolant... so I'm stumped.

Is this a common problem?
 

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Meh.
I has wagons.
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12,372 Posts
Are the fans coming on?

Also, the Phase II engine rarely leaks internally. If the HG starts leaking, it is usually weeping oil and/or coolant. If these stay topped up, not an immediate repair need.
 

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2001 Subaru Outback Wagon 2.5 5MT
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Discussion Starter · #3 ·
I will double check fan operation. The reason why I didn't bother is I have no low speed or idling overheating issues. And good to know about the external HG issue.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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are you losing coolant? does it get pushed into the overflow bottle?

was an aftermarket t'stat installed? (one not from a dealer?)

any maintenance/wrecks/mods done before you noticed this?

are you due for a timing belt?
 

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2001 Subaru Outback Wagon 2.5 5MT
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51 Posts
Discussion Starter · #5 ·
Coolant is full. Cannot confirm thermostat. All maintenance "supposedly" done by previous owner (cannot confirm dealer has no papers). Dealer I purchased from states timing belt was done (will confirm soon by inspection).
 

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2001 Subaru Outback Wagon 2.5 5MT
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Discussion Starter · #6 ·
I'm leaning toward some lack of coolant flow though. I found some little particles of something in the coolant. Probably sealant from a coolant flush that was done but it also might be silicone from the water pump being replaced and silicone being applied too liberally. I'm gonna throw a thermostat and coolant flush at it and see if it helps.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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7,355 Posts
Lets start off with the Basics. Replace the T-stat with one from subaru and the cap and go from there.
 

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2001 Subaru Outback Wagon 2.5 5MT
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51 Posts
Discussion Starter · #8 ·
One thing my car is missing the stock belly pan (skid plate, etc)... this may be the problem eh? My only thing is I bought the car 3 weeks ago and this problem just started a few days ago. :/
 

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2001 Subaru Outback Wagon 2.5 5MT
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Discussion Starter · #11 ·
Hmm rust in California? o_O

I know that water pumps can have that problem but I'm not convinced that's it. I'll tear it down if we can't narrow it to the radiator or thermostat.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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Hmm rust in California? o_O

I know that water pumps can have that problem but I'm not convinced that's it. I'll tear it down if we can't narrow it to the radiator or thermostat.
his point has more to do with corrosion inside the cooling system. You said you saw some debris and, IF , someone in the past has ever run straight water or perhaps an improper type of coolant - rust/corrosion could affect the pump and other internal parts. If that pump were made of substandard alloys, the vanes could have eroded away. That would lead to BOTH partial blockage and reduced pump efficiency.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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You may have a clogged radiator, especially if you saw things floating around in the fluid.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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You may have a clogged radiator, especially if you saw things floating around in the fluid.

I wonder if an infrared thermometer would show cooler sections of the radiator?
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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It will, as the traditional method is to touch it with the palm of your hands.
 

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2001 Subaru Outback Wagon 2.5 5MT
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51 Posts
Discussion Starter · #16 ·
Yeah I'm actually suspecting a blockage in the radiator as the chunks I saw were/are definitely either sealer or silicone. I'm gonna do some feeling of the radiator tomorrow.

BTW I'm an ASE certified tech (not gloating... well maybe a little) turned service manager the last few years, so I know what's up. I just hate diagnosing cooling system issues so I wanted some input as to common failures before I start taking stuff apart.

Also if anyone has rebuilt the 5MT before and has some tips on replacing the viscous coupling unit I'd like to hear about it. I'm gonna tackle that at some point this year before it starts snowing up in the hills.
 

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2011 Forester XT touring
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Maybe someone put in an aftermarket waterpump and the vanes have rusted off...
I had a similar thing happen where the vane/impeller was free spinning on the water pump shaft. Different car though. Chevy with a V-6. Same exact symptoms though.
 

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2001 Subaru Outback Wagon 2.5 5MT
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51 Posts
Discussion Starter · #19 ·
I know the corroding/melting impeller problem is common on domestics (Ford 3.0 V6 I think is very common).

Nipper: Thanks for the write up! Seems like it's not worth $600 to sublet the replacement we can definitely take care of that easy.
 

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2001 Subaru Outback Wagon 2.5 5MT
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Discussion Starter · #20 ·
So got out the infrared thermometer and checked for cold spots in the radiator, sure enough there's a portion of the center (in between the two fans) that remains under 100 degrees when the rest is around 150+. Leads me to believe there is blockage in there.

Sounds like I'm getting a new radiator and thermostat! Thank goodness it's not head gaskets (yet lol).
 
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