See full version: Tell-tale signs of a blown head gasket
The final, most noticeable symptom is a big cloud of smoke pouring from the exhaust, and the engine gauge showing maximum temperature after a few minutes. Unfortunately, these symptoms often arrive when it is too late to sort the problem out. more
Having trouble with your car, but not sure if your head gasket is the issue? You may want to look out for these common signs of a blown head gasket:
Blowing your head gasket is a common problem for motorists – especially if you have an older car. If you’re not careful this can result in damage to the engine and high head gasket repair costs. You could even require a mechanic to replace the head gasket entirely, for no small cost.
Luckily you can identify a number of common symptoms of a blown head gasket early on – providing the opportunity to save yourself time, money and hassle.
Engines are happiest when everything stays where it belongs: oil in oil passages, water in water jackets and combustion gases in the cylinders. That's the natural order of things. But a blown head gasket can result is an engine that sometimes breathes oil, lubricates itself with coolant and tries to cool itself with hot exhaust gases. Somewhere in this chaos are the exact symptoms you need to confirm the failure; you just need to know where to look.
The old mechanic's spot-check for combustion gases in the coolant is to remove the radiator cap -- with the engine cold -- start the engine and smell the gases coming out of the radiator. Sometimes leaks like this won't become apparent until the engine heats up and the metal has expanded, so it may have to idle up to to temperature first. Exhaust gases in the coolant are often immediately visible as fizzy bubbles rising through the coolant with the engine running, and are often recognizable by smell to a trained nose. But if your nose isn't trained, or you don't want to stick your face near churning, boiling water, you can use a "block checker"-type dye tester. These kits use a special dye that turns from blue to yellow or green in the presence of combustion gases. The kit comes with a test cylinder that you fit over the radiator cap opening; if the fluid changes color after exposure to the gases from the radiator, you've got a blown head gasket, cracked head or cracked block. [links]
This is a classic sign of a blown head gasket, but can be difficult to recognize if you don't know what you're looking for. Unless you allow the engine to sit for days, coolant in the oil won't simply pool on top of the oil in the oilpan. If that were the case, you'd see water on the dipstick above the oil line when you checked it. Most of the time, though, the water will emulsify into your oil like vinegar in a bottle of Italian salad dressing after you shake it. The tiny bubbles will cause the oil to get lighter in color and go very opaque -- this is the dreaded "chocolate milk" of head gasket failure. If your oil is cleaner because you just changed it, it will be the same color, but be very opaque and hazy. Water-tainted oil also tends to run down the dipstick in odd ways, parting, separating and beading off instead of coating the dipstick smoothly. You may also see and smell steam coming from inside the engine when you remove the oil fill cap. here
The head gasket plays a very important role in the function of your car's engine, and a blown head gasket can cause serious damage and lead to major repairs. A head gasket is a seal that is fitted between the piston cylinder head and the engine block. The car's engine is an internal combustion engine. For combustion to occur inside the piston chamber, high compression pressure must be achieved. The head gasket seals the combustion process and prevents the coolant and engine oil from mixing together in the combustion chamber. A blown head gasket can cause engine malfunction and significant loss of engine power [source: Bumbeck]. Let us now learn how to tell if you have a blown head gasket.
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To start with, the gasket has to isolate oil and coolant ports and combustion chambers to prevent internal and external leaks. It also has to withstand extreme temperatures and pressures that are constantly changing. A head gasket has to withstand temperatures that can reach 400°F (204°C) between the cylinder and block, and 2000 to 4000°F (1093 to 2204°C) at the fire ring exposed to the combustion chamber. here
Of all the gaskets used around your car engine, the head gasket has one of the toughest jobs. more
Because of the rough conditions under which it has to work, head gasket construction has improved greatly during the last years to increase clamping pressure and physical resistance. [links]
On top of that, the head gasket has to fight corrosion and chemicals, and withstand the rubbing force from the cylinder head (especially aluminum built ones) expanding as it goes from cold to operating temperature. The gasket does all this while frequently filling minor distortions between the head and block surfaces and vibration during engine operation. [links]
Then, besides extreme temperature changes, a head gasket has to resist extreme pressures that go from negative (vacuum) to positive (usually 1000 psi (6895 kPa) or more), as each piston goes through its four stroke cycle. [links]