how likely do i have a head gasket failure/cracked head?

[tootsie]

1997 4runner with 200k miles was sitting for a couple weeks while I was away, and when I ran it again upon coming back, sweet white smoke started billowing from the tail pipe. before i went away on my trip, i've been driving the car everyday with no problems, although I did suspect something cause the exhaust smelled sweet only when i started it in the morning, but the smell would go away after driving it for a bit. I did a block test that also came out negative. theres no overheating and no engine codes, although I did have a misfire code on cylinder 3 which went away after replacing spark plugs a few months ago (the spark plug in cyl 3 was seized, and we rethreaded the sparkplug hole).

my question is could this be anything else except a blown head gasket/cracked head?

 

[AuSeeker]

It's sound like the most likely possibility, when you run it and then park it overnight coolant leaks past the head gasket and into the cylinder, onxe you start it the coolant burns off, the next test would be to pull the plug and insert a bore scope/snake camera into the suspect cylinder and see if there's coolant on top of the piston.

If you find it is the head gasket and you can't afford to replace the gaskets you may want to try one of the head gasket leak sealer products.

 

[brillo_76]

Unlikely, you can do radiator leak down test to verify. You mostly can see the external coolant leaks and smell them.

 

[tootsie]

Unlikely, you can do radiator leak down test to verify. You mostly can see the external coolant leaks and smell them.

unlikely that it is headgasket leak? or unlikely that it isnt?

 

[brillo_76]

unlikely that it is headgasket leak? or unlikely that it isnt?

Oh its an head gasket or cracked head for sure. The head gasket leak can be verified with the leak down test. The white fog and sweet smell on cold startup is a dead give away. Wither its the head cracked or the gasket at this point is irreverent. Another way to check is to take out the plugs and use an inspection camera to see the coolant coming into the cylinder.

On a ice cold engine remove the radiator cap, you see bubbles in the coolant too as the either a crack head or bad head gasket as you will have compression psi leaking into the coolant system as well. You would see the coolant externally if it was just leaking out would be dripping on the ground under the rig.

If the engine got hot anytime in the past. It warps the head or cracks them between 2 valves... Very common if the Engine went to H. The cast blocks can take that heat the aluminum heads can not.

Compression test will also show you were the issue is which cylinders as well. Hopes this help clarify along with ways to narrow it down.

 

[mtbtim]

Guaranteed your head is cracked. It cracks between the valves and once the crack migrates to a coolant jacket, coolant can leak into a cylinder. The reason why you get smoke and a misfire in the morning is because when you shut down the vehicle and let it sit overnight, the cooling system is still under pressure. That pressure finds it's way out via the crack in the cylinder and allow coolant to pool on top of the cylinder head. When you first start it, the coolant fouls out the spark plug until the coolant burns off (white smoke) and then the cylinder fires normally. The #3 cylinder is notorious for cracking. You either spend the time and money to replace heads or you put the money towards a rebuilt engine. After replacing heads on these engines twice, I'd much rather put the time and money into getting a quality rebuilt engine. My Timmy the Toolman YouTube channel has video series for both ways to go.


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