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Discussion Starter · #1 ·
Gentlemen....looking for confirmation that I'm not a complete dolt (doubtful).
I've had overheating issues with my 2005 outback. Installed an aftermarket thermostat ($6) and it did NOT work so put in an OEM thermostat ($35) which did (lesson learned). Still had issues - found that the drivers side fan was not working - took it apart, cleaned it, buffed the armature, now works well. These fixes helped a lot but car is still overheating at low revs...ie. stop and go driving....when the revs get above 2000 the engine cools to where it should be after a few seconds. Highway driving the gauge is rock solid where it should be. Seems to me this is a water pump problem....at low revs it is not pumping adequate coolant thru the system...BUT...the pump only has 4 years and 40,000 miles on it. It's an OEM pump that I had installed when I bought the car. I'd hate to pull the pump only to find no problem there...could it be something else?
Thoughts??
 

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Meh.
I has wagons.
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Are the fans coming on as they should?

Have you burped the cooling system? It helps to have the front end elevated.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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any signs the cooling system has been 'abused' by previous owners?

could be partial blockage from corrosion/debris in rad or heater core
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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Gentlemen....looking for confirmation that I'm not a complete dolt (doubtful).
I've had overheating issues with my 2005 outback. Installed an aftermarket thermostat ($6) and it did NOT work so put in an OEM thermostat ($35) which did (lesson learned). Still had issues - found that the drivers side fan was not working - took it apart, cleaned it, buffed the armature, now works well. These fixes helped a lot but car is still overheating at low revs...ie. stop and go driving....when the revs get above 2000 the engine cools to where it should be after a few seconds. Highway driving the gauge is rock solid where it should be. Seems to me this is a water pump problem....at low revs it is not pumping adequate coolant thru the system...BUT...the pump only has 4 years and 40,000 miles on it. It's an OEM pump that I had installed when I bought the car. I'd hate to pull the pump only to find no problem there...could it be something else?
Thoughts??
miles on car?

miles on radiator?

miles on OEM rad cap? (no subs on a OEM rad cap).

and is this 2005 a H6, H4 plain, or H4 turbo.?
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Have you checked the space between the radiator and the AC condenser for blockage? When I checked my '01, it was 1/3rd blocked with leaf material.

Do you know that the fans are actually running and starting at the proper temp?
 

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2002 Outback 2.5 Base ---- 2008 Outback 3.0 L. L. Bean
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Carefully, put your hand at different parts of the radiator to feel if there is a cool spot or area. It should be very hot all around so be careful. Naturally watch the fans but you do this behind the grill. My radiator had a cool spot right in the middle. I would overheat in different conditions. I changed hoses, cap, coolant, w-pump and thermostat (always use thermostat from dealer). Finally changed radiator and have been great ever since. Also feel top and bottom hoses, they should be very hot! Be careful of moving parts and heat!!
 

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Discussion Starter · #7 ·
My 2005 is a 'plain jane' 4 cylinder with 175,000 miles. Thermostat is new and OEM. Fans are definitely working when car is overheating. Rad cap is OEM - not sure of age. Overheating is very consistent with engine revs. Gets hot at low revs - cools immediately and consistently when revs are raised.
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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are you losing coolant? (level low in radiator) is it being pushed into the overflow ?
 

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2019 Outback 2.5i Premium
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A lot of these threads put off addressing the elephant in the room, probably because of other cheaper fixes to try first, but it's almost always bad head gaskets. Check the coolant for contamination from the exhaust. Even if you don't see obvious contamination, if air keeps getting into the system that's likely the problem.
 

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I'd vote for degraded performance due to blockage in either the radiator or heater core.

It sounds like you've addressed the fan situation, and you've got a good thermostat.

Subaru water pumps are extremely robust, so I hesitate to think that's the problem.

But if the rad is blocked externally (leaves & bugs) or if it is clogged internally with mineral deposits, then it will have a hard time cooling the car at least until you hit the right conditions for maximum air and water flow through it.

Similarly, an internal restriction in the heater core can prevent the thermostat from doing its job. The thermostat depends on being bathed in hot water returning from the cabin. You don't get hot water back from the cabin unless it was hot to begin with and the heat wasn't actually extracted in the cabin, and of course all of that depends on good water flow through the core as driven by the pump.
 

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A lot of these threads put off addressing the elephant in the room, probably because of other cheaper fixes to try first, but it's almost always bad head gaskets. Check the coolant for contamination from the exhaust. Even if you don't see obvious contamination, if air keeps getting into the system that's likely the problem.
Coolant-to-combustion breaches are rare in this model. (Note, they are highly susceptible to a different type of head gasket failure instead)

Combustion breaches are very common in the older DOHC 2.5 engine, perhaps you are thinking of that?
 

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2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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My 2005 is a 'plain jane' 4 cylinder with 175,000 miles. Thermostat is new and OEM. Fans are definitely working when car is overheating. Rad cap is OEM - not sure of age. Overheating is very consistent with engine revs. Gets hot at low revs - cools immediately and consistently when revs are raised.
I would remove and rinse out the radiator (inside and out), and maybe consider just buying a new radiator at that kind of miles. ...with a new OEM rad cap for it.

edit:

and I deleted a bunch of other stuff from a guy with a 2.5 turbo (that car should have its own thread if need be,
probably here where they all live,...and breed : http://www.subaruoutback.org/forums/109-gen-3-2005-2009/ )

such as a turbo is quite a different animal then this plain jane 2.5, and updated this thread title.
 

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Adding to what has already been mentioned/suggested . . .

In regard to the fans, they might be turning, but are they turning at the right speed? There's a pair of green connectors under the dash. They are normally not together, but when connected and the ignition is turned to On, the ECU will cycle the radiator fans (among other devices). The two fans (they always run together) will begin at off, increase to what is a relatively slower speed, and then switch to high speed before turning off and the cycle repeats. With the hood open and watching the fans, the speed changes in both fans should be apparent visually and by the "roar" they make. Might be an idea to check this out. (Engine remains off for this test.) The two green "test mode connectors" are probably found in the front right foot well area at or under the forward edge of the floor carpeting. (Remember to disconnect them when the test is complete.)

Also, when the car is stopped and idling, the temperature gauge is even marginally above normal, and the radiator fans are running, have you tried turning on the car heater at the hottest temperature and fan on high speed? If there's flow through the heater core, the added heat being withdrawn from the coolant should lower the gauge back to normal, or at least have a noticeable impact. (Set the HVAC to take in outside air, not recycle. Also this works if the cabin air filter isn't blocked -- if the car has one.)

Fans are definitely working when car is overheating.
Because of the way the gauge is programmed, the fans should come on even before the gauge begins to go up, and be on (high speed) if the gauge is a pointer width or two above normal.
 

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Discussion Starter · #14 ·
Lots of good ideas...many thx all.
Since I'm not losing coolant and there doesn't seem to be any contamination from a bad gasket (and the gasket and head were redone 40k miles ago)....I like rastermans suggestion. A blocked rad or one with decreased flow thru it would I think produce the symptoms I'm seeing...ie. better cooling with increase in revs - and consequently more coolant flow thru the rad. I'll see about getting a radflush or what other options are available in that area.
cheers
 

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A brand new radiator is only about $120. The radiator/fan assembly is easy to remove as one unit. I did that to give myself more working room when changing my timing belt and it only took a few extra minutes. You might want to consider just buying a new one and be done with it.

Make sure you use either premixed coolant or 1:1 coolant concentrate:distilled water and not hard water.
 

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Discussion Starter · #16 ·
Good idea on the new radiator....by the time I invest the time and trouble and expense of cleaning the old one - may well b worth it.
cheers.
 

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A little tidbit of "old guy" talk

In the old days of soldered metal radiator tops, "rodding out" the radiator was a viable alternative to buying a new one. I had a 1986 Toyota 4Runner and every 2 years, the engine started running hot. I eventually learned that the radiator gets plugged up so I found a shop that would desolder the top, rod out the radiator and seal it back up for $50. Worked like clockwork. I got to the point of being able to take the radiator out, drive it to the shop in my wife's car on a Saturday morning and get the "like new" radiator back that afternoon with no more than about 45 minutes invested in the job including the drive to/from the shop. The original radiator lasted the life of the 4Runner (238k miles and 15 years).

Nowadays with crimped-on plastic radiator shells, the radiators are virtually an expendable item.
 
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