Impreza overheating light coming on

[walkerjc]

I have a 2010 Subaru Impreza 2.5i non turbo that i bought about a year ago. The guy who had it before me redid the head gaskets and some general maintenance. I have put maybe 1000 miles on it and it now has a p0137 code (which isnt really a concern to me, just thought to mention it for context?) and the overheating light came on flashing and then solid after driving for about 20 minutes. I pulled over and let it idle until the light went away and kept driving for about 30 minutes slower, with no light. When i drove it again, the light came on same as before and i stopped and it went away, just like before. I had the heat inside the car on max, btw, it was around 25 degrees fahrenheit. I got out and looked at the cooling fans and they were both running smoothly and well, so they arent the problem. I thought it could be a thermostat or maybe a bubble in the coolant system somewhere? I do realize it could be the head gaskets even though they were changed in the last 2000 miles but i think it is unlikely.

so to sum up:

problems:
p0137 code (not really concerned abt more for context)
overheating light came on after about 20 minutes of driving

recent maintenance:
oil change about 1000 miles ago
head gaskets within 2000 miles ago
spark plug wires within 2000 miles ago

misc. info:
abt. 182k miles
manual transmission
completely stock besides wheels

Im really only concerned about the overheating light and would appreciate any amount of knowledge and information regarding possible problems and fixes, thanks in advance. I will be testing for a few thing and will update on that later.

 

[GuyS1]

Are the symptoms just the light coming on? Head gasket failure is a common cause of overheating. If the gasket was replaced and the head was warped and not machined true, that would explain an early failure of the recent head gasket. If the head gasket has failed then you’d be losing coolant as well as overheating. But sometimes the leaked coolant isn’t readily visible and doesn’t drop the coolant level in an obvious way. When my headgasket was gone, the coolant leak was noticeable only on the top of frame/crossmembers. It wasn’t visibly obvious, and my car actually wasn’t even overheating. What tipped me off was the small of coolant. When I took it to the Subaru mechanic, he highly recommended I had the head machined, which I did. That was 60,000 miles ago. No problems since.

 

[walkerjc]

Are the symptoms just the light coming on? Head gasket failure is a common cause of overheating. If the gasket was replaced and the head was warped and not machined true, that would explain an early failure of the recent head gasket. If the head gasket has failed then you’d be losing coolant as well as overheating. But sometimes the leaked coolant isn’t readily visible and doesn’t drop the coolant level in an obvious way. When my headgasket was gone, the coolant leak was noticeable only on the top of frame/crossmembers. It wasn’t visibly obvious, and my car actually wasn’t even overheating. What tipped me off was the small of coolant. When I took it to the Subaru mechanic, he highly recommended I had the head machined, which I did. That was 60,000 miles ago. No problems since.

I worked on it today and found that the coolant was a bit less than 1/2 gallon low, I topped it off and will be looking for coolant leaks and lower coolant levels. I plan to change the coolant out all together here in the next week or so. I do think it is very possible that the head gaskets are bad and warped heads with no machining could be a likely cause of premature failure. Thanks for the reply and advice, really appreciate it.

 

[bmart]

I have also heard of guys just doing the gaskets wrong or damaging them during install. If you have clogged coolant channel/hose anywhere... Was the thermostat replaced or at least tested when he did the work? Driving it hot will do nothing but create the potential for more damage. 20 minutes is a long time. You can dye the coolant and see what is going on with an inexpensive pressure tester.

 

[walkerjc]

I have also heard of guys just doing the gaskets wrong or damaging them during install. If you have clogged coolant channel/hose anywhere... Was the thermostat replaced or at least tested when he did the work? Driving it hot will do nothing but create the potential for more damage. 20 minutes is a long time. You can dye the coolant and see what is going on with an inexpensive pressure tester.

I tested some things a few days back, the lower coolant hose was empty when the motor was cold, and the hose filled up once the motor was warm. This would indicate that the hose is not being clogged, and that the thermostat is working (opening at temperature to allow coolant to flow). I'm not sure if it was replaced or tested thoroughly when the head gaskets were done though. I agree that 20 minutes is a long time for it to overheat, and another interesting part was that when the overheating light started flashing, I pulled over and let it idle until the light came off.
Anyway, all evidence seems to point towards head gaskets gone bad, so I plan to do a leak-down test sometime soon.

Thanks for the advice.

 

[walkerjc]

* UPDATE *

the check engine light was something electrical going back to the sensor and is resolved, so it has nothing to do with the over heating as suspected.

 

[GuyS1]

Oh. Was it a wire? Or was it an electronic or ECU like fault?

 

[walkerjc]

Oh. Was it a wire? Or was it an electronic or ECU like fault?

Pretty sure just a wire grounded out somewhere. The wires were not tied down (probably from when the last guy did the head gaskets), so I tied them with a zip tie to hold it and after I started the car the light went away.