Can a head gasket sealer fix combustion gases leaking into my cooling system?

I have a 2005 Honda Civic that seems to be leaking combustion gases into the cooling system. No external leaks and no signs of oil in coolant, but the car would heat up after a good 30 min drive. Since the vehicle is old, I’m not sure if I want to get an expensive repair or seal it with a head gasket sealer... show more I have a 2005 Honda Civic that seems to be leaking combustion gases into the cooling system. No external leaks and no signs of oil in coolant, but the car would heat up after a good 30 min drive.

Since the vehicle is old, I’m not sure if I want to get an expensive repair or seal it with a head gasket sealer (mainly because im not sure if it will actually fix, and if it is good long-term).

Any ideas?
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