Subaru Outback Overheating

My wife has a 2011 Subaru Outback 3.6R that has been overheating intermittingly over the last year. It has around 165k miles and so far we have had the fans, fan module, and thermostat replaced. Two days after the thermostat was replaced, I had driven it for 2 hours mostly at highway speed. I was sitting in a parking lot and the AC got warm/hot and the flashing red overheat icon came on so I turned it off.

We purchased it used from a dealership and my father went with my wife and used one of the head gasket testers that you stick in the radiator but I’ve since read that head gasket failures don’t always present exhaust gas in the coolant. Does this sound like a head gasket failure or could it be something else? I feel like I’ve thrown money at this car since day 1 and don’t want throw any more if I don’t have to.

This should be in the owners manual, but it’s not.



Have you verified that the cooling fans are operative when the A/C is engaged?

Has overheating happened with the A/C off?

Last question. Has there been any service work done on the A\C system which involved recharging?

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Is it losing any coolant?

My mind leaps immediately to head gasket when I hear overheating and Subaru.

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When it is parked, the cooling fans will turn on then off, they won’t stay on. The overheating has happened in cold weather. That was the first time and the fans were the original ‘solution’. I asked to have the AC recharged. My local, non-dealer, mechanic said it would only take a little.

Not that I’m aware of.

I understand this is a joke but I really wish they had a gauge over the blue/red idiot lights.

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I have never seen a joke from @tester

This is why it’s rarely wise to buy a used Subaru.

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I had serious reservations and a very stubborn wife.

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The Subaru might now be junk. Throw the keys at your wife and scream "now look what you’ve cost me!.

Could be a head gasket, but also could be something else. Coolant leaking into the combustion chambers can (if sufficiently severe) present as exhaust at the radiator and/or as white smoke at the tailpipe (I believe there is an electronic sniffer for this), and as fouled spark plugs. One can perform a cooling system pressurization test and a combustion chamber leak down test to detect leaks to the combustion chamber. Coolant leaking to the oil should show up in the oil (it froths up like a milkshake, and if really bad “oil” level can rise).

A blocked radiator can cause overheating and newly replaced parts (thermostat, fan switch, etc.) can go bad. An improperly oriented thermostat will give problems. Low coolant will cause overheating. Sometimes water pumps stop working (plastic impellers, if it has one, can spin on the shaft). Is the serpentine belt intact, not slipping?

Either you or a competent mechanic should check these before concluding it’s a head gasket, which are pricey. If it is a head gasket, it’s recommended to replace both of them.


If it is not overheating when driving at normal road speeds it doesn’t necessarily sound like a head gasket issue. Does the overheating only happen when stopped or idling? Who replaced the thermostat and was it aftermarket or OEM?

Anytime the engine is overheating the radiator fans should be spinning like a banshee. Next time it happens, leave the engine on, get out of the vehicle and pop the hood. Are the engine compartment fans spinning like crazy?

If the answer is “no”, then you have a fan or fan control problem.

If the answer is “yes”, then you could have one or several problems. Common among them:

  • Radiator cap isn’t holding pressure
  • Coolant level is low
  • Air in cooling system
  • Water pump faulty
  • Radiator faulty
  • Thermostat faulty
  • Temperature gauge faulty
  • Head gasket faulty

Chemical tests on the coolant and a cooling system pressure test are both commonly used by mechanics for head gasket problems. It isn’t always possible to verify the head gasket is the problem until the head is removed for a look-see. In that case experienced mechanics know how to eliminate most of the possibilities, and if nothing found they’ll presume it a head gasket problem.

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The fan cycling on and then off after engine shutdown is normal. The exact complaint is still a bit murky to me as to when that overheating occurs and whether or not it’s losing coolant, but I might throw out a few possibilities.
One is a weak pressure cap for the cooling system. Cheap and easy. Caps can get weak with age.
Second could be a missing lower radiator air duct; or deflector.

Personally, I would not get all bent out of shape over your Subaru. The 6 cylinder is not known for head gasket problems. Unless severely overheated, even the 4 cylinders are not particularly prone to blown head gaskets. The issue there is oil or coolant weepage which if managed correctly will not be a problem although no weepage is preferred.

I asked about A/C on the off chance that someone may have overcharged the system.

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WE see very few complaints about the 6 cylinder Subaru overheating. More complaints about the 4 cylinder ones blowing head gaskets than all other cars combined.

How Subaru got such a sterling reputation escapes me. Th`y are the darling of the consumer reports crowd.

I have never purchased one because I have never needed the complications of all wheel drive in my life.

Bedsides, it never snows near Buffalo, NY in the winter (yes, that’s a joke.) Front wheel drive is ok, but I actually would prefer rear wheel drive in the winter. It is the most fun and after 3 million miles of driving a big rig and 15 years of driving a school bus, all my reflexes are geared for rear wheel drive.

If you don’t like subarus-don’t buy one-that’s why I don’t have a toyota-I’m getting my 9th next weekend. :no_mouth:


The 3.6 wasn’t really prone to head gasket failure. If you let it overheat you might have damaged them.

Look at the bright side, lots of new Subarus have serious problems.

Head gaskets don’t make the car junk, just another big expense.