Cooling
Overheating in traffic: fan fuses, radiator end tanks, thermostat and cap
The gauge climbs in city driving and drops on the highway when a fan circuit is dead; the 2005 XT has two fans on separate fuses. Older cars also crack the plastic radiator end tanks at the upper hose or crimp seam, and a tired thermostat or cap finishes the job.
Frequency basis: One well-documented 2005 XT case (temperature climbing at idle, fixed by a blown main-fan fuse) in a thread with 419k views, plus generation-wide radiator plastic-tank cracking documented by owner logs and a parts guide. Overheating itself is uncommon, but it is the fastest route to a head gasket job on this engine.
Symptoms
- Temperature rises at idle or in stop-and-go, normal at highway speed
- One or both fans do not run with the A/C on (they should start immediately)
- Coolant seep or crust at the upper hose neck or along the tank crimp; coolant smell after a drive
- Reservoir level dropping with no visible leak
Causes found
- Blown sub-fan or main-fan fuse (fuse 3 feeds the low-speed series circuit, fuse 4 the main fan at high speed), often from a corroded or wet fan connector
- Fan relay failure
- Brittle plastic radiator end tank cracked by heat cycling
- Thermostat sticking or a radiator cap that no longer holds pressure
- Air pocket after a coolant change that was not bled
Check in this order
- Turn the A/C on with the engine running: both fans must start at once. If not, check the fan fuses and relays first, then the connectors
- Pressure-test the system cold and inspect the end tanks and hose necks with a light
- Test the cap with a cap tester; replace the thermostat with a Subaru unit if it is old
- Bleed the system properly with the nose up after any coolant work
What fixed it
- A new main-fan fuse cured the 2005 XT case outright; find why it blew
- Replace a cracked radiator (sealers do not hold on plastic tanks); all-aluminium aftermarket radiators (Koyorad, CSF, Mishimoto) avoid the plastic tanks
- Do the thermostat and cap with the radiator and refill with Subaru coolant
- Do not drive an overheating turbo car: head gasket and turbo damage follow quickly
References on this site
OEM parts
- 45111AG09ARadiator complete
- 45161AG00AHose, radiator inlet
- 73311AG01ARadiator fan motor and impeller
- 45124AC000Air plug, radiator (bleed)
Factory manual chapters
Maintenance guides
Sources
Forum threads are owner reports, not factory findings. Counts are from the threads and complaint records read for this page; read the sources before buying parts.
- 1.2005 XT Heating up/overheating
subaruoutback.org · Forum thread · 2010, blown main-fan fuse; fan fuse circuit explanation
- 2.2005 Subaru Outback XT overheating w/AC on
cartalk.com · Forum thread
- 3.Subaru Outback Radiator Guide for 2000-2010 Models
go-parts.com · Article · vendor guide: plastic end-tank cracking pattern
- 4.Radiator crack filler
subaruoutback.org · Forum thread · sealers do not hold on plastic tanks
- 5.2006 OB XT aftermarket radiators?
subaruoutback.org · Forum thread