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Air in cooling system - head gasket leak?

(1995 Chevrolet Cavalier)
in Huntington, NY on January 03, 2009
My cooling system constantly pushes out whatever coolant I put into it. If I don't watch it, it overheats. The coolant is being pushed out by air, but no matter how many times I fill it and bleed it, there is still air getting into the system, and not much coolant getting out. Is this definitely a head gasket leak or could it be something else?

It seems like the "air" mostly gets into the system with the engine running. It definitely gets some air introduced while it is warming up (but not after it has warmed up?), and there is a sudden surge of pressure when I shut down the engine, which is worse after it has warmed up.

I drove it 800 miles recently with no problems, but driving half an hour to work every day causes it to push out all the coolant and/or overheat.
Displaying 5 answers & 8 comments
Popular Answer
on May 02, 2010
Sounds like this could be a blown head gasket or cracked head. The best test, short of the chemical "Blok Check" is start it up cold. Run just above idel for one or two minutes. Then shut the motor off. Carefully remove cap: If there is pressure, it came from combustion, not the engine heating up. If there is pressure, it could have only come from combustion gasses buidling up.
on January 05, 2009
Is there any apparent leak that you can see? Do you see white smoke from the exhaust? Check your oil dipstick for oil and coolant intermix. It will look like a mayonnaise that has turned. Does the coolant smell like exhaust or gasoline? If the car has overheated, there is a good chance the head gasket has blown but it should be verified.
on January 06, 2009
Does the dipstick look ok? Often when the coolant and oil mix, you'll see it on the dipstick. Oil doesn't really float on coolant like it does on pure water. Either way, if the oil or coolant didn't look normal, it would be obvious that one didn't look like it should.

You'll want to do a compression test to see if any cylinders are low. I would be careful doing a cooling system pressure test because if coolant is leaking into the cylinders, you don't want to hydro lock the engine. It's important to figure out where the coolant is going because if it is a basic leak, that will save you a head gasket. Your front passenger floor carpet isn't wet is it?
on January 06, 2009
If you leave the spark plugs out when you first turn over the engine, you should be ok. Be careful when you crank it, water really shoots out of the plug holes! And yes, you should be able to see which cylinder(s) might be leaking. Good luck!

Most cooling systems should be able to maintain 14-15 psi. Thankfully the oil still looks ok. It's a mess when there's intermix
on April 06, 2009
Thanks for the update. Torque-to-yield, or stretch bolts should always be replaced when removed as they are one time use. Many shops with a smog machine can use their emissions sniffer to check for exhaust gasses in your coolant tank. They don't submerse the sniffer but the fumes off the coolant will show a reading if the combustion is leaking
on January 05, 2009
I don't see any leak.

I don't see a lot of smoke, but it's winter so it's hard to tell smoke from steam.

I don't see any foam or coffee in the oil fill, though I haven't opened anything up or checked the oil pan.

The coolant doesn't have oil floating on it, and smells like coolant. It gets a little brown over time.
on January 06, 2009
No, the dipstick looks normal. I think it's a leak from the cylinder directly into the coolant. It only gets air in the system while the engine is running (especially when I turn it off), and the coolant level stays the same unless it spills over at the pressure cap. I will try to do a pressure test. If I take the spark plugs out before pressurizing the coolant, I don't need to worry about hydrolock, right? Any coolant will squirt out of the spark plug holes when I turn the engine, and I will see which cylinder has the leak.
on May 31, 2010
I was told I had a leak in my head gasket but that they were able to fix it "chemically." However I am still experiencing overheating and loss of coolant and my passenger side floor carpet does get wet. Can any one suggest what to do next? Please!!
on June 30, 2010
change the heater core it's a little radiator inside the dashboard probably has a crack in or something in it which is causing coolant to leak inside the car on the floor board causing the engine to get air in the system causing the temperature to rise or go up and down maybe overheat at times which is dangerous if not replcaed that may solve your problem
on April 06, 2009
Could this be your water pump? It is a common problem in 2.4L engines and causes collant loss and overheating?
on April 06, 2009
It was the head gasket, leaking combustion gases into the coolant. Last time they repaired the head gasket they didn't replace the torque-to-yield head bolts, so they were stretched and not tightened down enough.
on June 13, 2012
I had a 1990 z24 Cavalier (which the overflow also acted as the filler...) I would pour water in and it was fine for a little bit, then it would push all the water out the overflow... when the car was running and thermostat open, it would "perk" out of the jug... I thought it was a head gasket, but I replaced the water pump and it fixed the problem. My water pump for that car only cost $32 for a lifetime (which was a smart choice because it went out again 2 years later). That has been my experience. Check for steam/white smoke coming from the exhaust, and check your oil to see if it's level has raised or it is white (meaning water is being pushed into the oil). Also check your hoses and thermostat. All are relatively inexpensive fixes (excluding the head gasket). Always start with the cheapest fixes first when the problem part isn't obvious
on September 21, 2010
Make sure that your thermometer is in the right way up. My cavalier did this as well, I could drive it and it would be fine but as soon as I turned the engine off all of the coolant came gushing out. I found out it was because the thermometer was upside down and an easy fix.
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