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 (mainly because i'm not sure if it will actually fix, and if it is good long-term).

Any ideas?

Doubtful as it's a compression leak - much higher pressure than an oil or coolant leak.

But a simple head gasket replacement should not cost a fortune - I have no mechanical experience or skill, but have replaced 3 myself on 4 cyl cars just by following the Haynes manuals!

Most of thes products are snake oil, or at best a get you home fix. First thing to try is to re-torque the cylinder head bolts; that might just be enough. After that it's head off and a new gasket. If you get on top of this pretty quick you can probably avoid having to resurface the head

Go rent a chemical combustion gas test kit from your local auto parts store. Basically it's a large syringe that you place into where your coolant pressure cap goes and it is filled about 1/3 of the way with the special blue liquid that turns yellow when combustion gases are detected in the coolant. You will have to purchase the liquid separately. This is the most simple, sure fire way of confirming a head gasket leak into the cooling system, and if you do detect combustion gases in the coolant, then it'll be up to you to decide whether or not you want to take the necessary action to repair it properly. If you don't, then consider other possibilities such as thermostat issues, cooling fan issues, restrictions, air pockets, or even water pump issues as well.

The chemical you describe is a total waste of money as it will do nothing to seal the leak. If you are short of cash buy the Haynes manual and do the work yourself. You may need a machine shop to correct the head surface if it is warped. A steel straight edge will reveal this. No light should show between the straight edge and the head surface.

The only way to fix a headgasket that's bad is to replace it. All the additives don't work worth a darn and just plug up the hydraulic lifters.

Don't count on it!

You likely have a WARPED aluminum cylinder head that was caused by a severe overheat.

Do you recall an incident when your temperature gauge was high and you kept driving the car?

The cylinder head gasket leaking is not the PROBLEM, it's the SYMPTOM. The problem is the warped cylinder head.

-Engine overhaul mechanic and general automotive mechanic since 1972

If it does, buy a lotto ticket too. It won't hurt to try, but don't bet the farm on it. Have the cooling system pressure tested before you go too deep. Combustion leaking into the cooling system usually comes through cylinder head CRACKS. Repair is $$$$$$.

Get the gasket sealer you add to the radiator, drive for 100 miles not exeding 3.5k rpm and do a coolant flush

Unless you're mechanical inclined, take it to a dealer. They'll check it & tell you how much it will cost. If the car has been good until now, consider the expense. Can you buy something else for that amount? Do you trust it?

They do work sometimes and somewhat but definitely not any answer. Replacing the gasket is the answer and not that hard. You have to spend about $100 for the gasket set and $25-$50 to have the head surfaced. That is total expense. A fancy sealer casts $40 and it may not hold up.