2012 Legacy overheating problems

[snads]

So car started overheating a few months back. Got it towed back to the house after starting it up a few times and driving < 5 min just to make sure it wasn't some weird fluke. Changed out the thermostat and refilled the system. It ran great for 2 months.

 

Was driving around town and it started overheating again with the same problems, coolant bubbling out of the overflow tank. Got it towed to the house again, this time I had little slices of what looked like black rubber in the coolant. I didn't want to think it was the head gasket since the car only has 90k miles on it. This time I changed bottom and top hoses, radiator, and I got a new gasket for my thermostat (thermostat I ordered was leaking for some reason with bottom pipe on). Ive been driving it around my block as there are a lot of hills by me, when it warms up it overheats the minute I try to go uphill.

 

Fans are running, bottom pipe is cold, is my thermostat bad again?? I have a heater core I ordered but before I do all that work I want to make sure it's not something dumb. I think I have all the air out?? I've ran it pulles the cap a while its hot and could hear air escaping but not 100% sure.

 

I have a heater core i ordered but I'm trying not to do all that work if its something stupid. The bottom pipe is staying cold when

[Alexmed2002]

You might need to pressure test the system. That will tell you whether or not you may have a blown headgasket.

[Sarang]

I wouldn't think that a heater core would cause it to overheat.

Stock Subaru thermostats are known to be very reliable.

 

The coolant is designed to get over 212 degrees inside the engine and not boil due to the pressure in the system. If you were leaking coolant, then it was not maintaining pressure and your coolant may have boiled in the engine. That would cause you to overheat very fast.

 

Last year my car overheated because of a very tiny pinhole leak in one of the small coolant hoses. Replaced the hose, filled it back up, and no more problems.