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Flashing Red Coolant light


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Hi, I'm new to this site and new to owning a Subaru. I just bought a 2010 Subaru Legacy 2.5i with 152,000 miles on it (I know it's high). I've been driving it for two weeks now with no problems. All of a sudden the coolant light starting blinking red when I was driving to work. I immediately pulled over and let it cool down. I checked to see the coolant is on the full mark. After 10 minutes I started it up back up and drove home. The light never came back on. My question is, would this be a blown gasket or something else?
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Out of curiosity, what was the temp outside when you were driving?

When you say the coolant level, did you see JUST water or JUST antifreeze in? Did it look like it was a mix (hard to tell sometimes, I know)?

 

Also, welcome to the forums!!

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The temp outside was around 50 degrees. Both fans work I checked that, it looked like the coolant was a mix but I couldn't tell for sure. It was definitely not just water. It was a dark greenish color.

Your coolant shouldn't be any color except blue... Also the Subaru Super Blue is pre-mixed and can be had from any Subaru dealer for $25-$30, or a bit cheaper from Amazon. If it's low add a little water FOR NOW and get it flushed and refilled ASAP. I've got almost 105k mi on my GT and it's first (to my knowledge) additional coolant was just after last summer and was literally 1/4 gal which pretty much filled the overflow. If you've lost more then that theres something else going on. Definitely get a pressure test done and make sure there's no bubbles (air) in the system as stated above.

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Your coolant shouldn't be any color except blue... Also the Subaru Super Blue is pre-mixed and can be had from any Subaru dealer for $25-$30, or a bit cheaper from Amazon. If it's low add a little water FOR NOW and get it flushed and refilled ASAP. I've got almost 105k mi on my GT and it's first (to my knowledge) additional coolant was just after last summer and was literally 1/4 gal which pretty much filled the overflow. If you've lost more then that theres something else going on. Definitely get a pressure test done and make sure there's no bubbles (air) in the system as stated above.

What if I didn't lose any coolant and it is dark blue, not green. I was mistaken by the color.

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To check if its a head gasket, check you're oil to see if its a milky texture. That means coolant is leaking into it and you definitely have a failed head gasket.

 

Look at you're exhaust, if its a blueish color you're burning oil. Another sign that oil is leaking into the combustion chamber. Another sign of a head gasket leak. If you're exhaust has a sweet smell that means coolant is burning off in the combustion chamber.

 

Subaru blue coolant has a 100k service interval. Once the coolant properties start to break down corrosion starts on these aluminum blocks. It's important to keep this fresh or you can clog the little fins in the radiator.

 

When you checked the coolant, did you look at the overflow or look underneath the radiator cap? Please don't do this after the engine is hot. Make sure its cool or you could get some serious burns and lose a lot of coolant.

 

Thermostats are super simple valves and rarely fail in these newer cars so I'd be hard pressed to say that is the case.

 

Another check you can do is if the car starts flashing hot, turn on the heater/defroster on high heat. If that starts to cool the car down there is a blockage in the cooling. Either an air pocket or a bad radiator.

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To check if its a head gasket, check you're oil to see if its a milky texture. That means coolant is leaking into it and you definitely have a failed head gasket.

 

Look at you're exhaust, if its a blueish color you're burning oil. Another sign that oil is leaking into the combustion chamber. Another sign of a head gasket leak. If you're exhaust has a sweet smell that means coolant is burning off in the combustion chamber.

 

Subaru blue coolant has a 100k service interval. Once the coolant properties start to break down corrosion starts on these aluminum blocks. It's important to keep this fresh or you can clog the little fins in the radiator.

 

When you checked the coolant, did you look at the overflow or look underneath the radiator cap? Please don't do this after the engine is hot. Make sure its cool or you could get some serious burns and lose a lot of coolant.

 

Thermostats are super simple valves and rarely fail in these newer cars so I'd be hard pressed to say that is the case.

 

Another check you can do is if the car starts flashing hot, turn on the heater/defroster on high heat. If that starts to cool the car down there is a blockage in the cooling. Either an air pocket or a bad radiator.

I checked all of that and everything seems to be okay. No oil or sweet smell coming from the exhaust. The oil looks like oil, no milky substance. I might change the coolant because I'm not sure when he had it changed. When I looked at it, I looked under the radiator cap, not the overflow.

 

I also forgot to mention that when I drove it home I had the A/C running on high.

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...Another check you can do is if the car starts flashing hot, turn on the heater/defroster on high heat. If that starts to cool the car down there is a blockage in the cooling. Either an air pocket or a bad radiator.

 

To clarify, when trying to cool the engine, do not run the front defrost or AC, just use the heat. The front defroster automatically engages the AC. Running the AC will put more load on the engine and heat up the condenser in front of the radiator.

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Red blinking light sounds like the ECU knew overheating was happening, so sensor seems to be working.

 

Turning on the AC just to get the fans running seems counterintuitive. It's like saying, well the human body sweats to cool itself off, so if I'm overheating I should run around the block so I can sweat more. :lol:

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  • 3 weeks later...
Update:I drove it for a couple weeks without it going on once. Then, this past weekend it started up again and wouldn't go away so I took it to the dealer and had them diagnose it. They told me the head gasket was just starting to go so $1600 later, its all fixed. Thanks you guys for helping me out!
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