If you’re wondering what it is that causes a cylinder head gasket to fail it could only be for one reason: You have a car with a blown head gasket. Bummer. Expensive too. At least it’s not terminal.
Let’s start off by explaining what a gasket does. If you have a container of some kind and it has a couple of parts that need to seal together so that whatever is inside doesn’t leak out you need a gasket between those parts so they’ll seal. Next time you open a jar look inside the lid. Around the edge you’ll see a rubber ring, that’s a gasket. The weather strip around your door is also a gasket, intended to keep the outside elements out and the nice comfortable inside air in.
Now, the engine in your car is made up of a bunch of parts and there are a number of gaskets used to keep the various fluids (including air) inside where they belong. The gaskets that have the toughest job are the cylinder head gaskets that go at the business end of the engine, between the engine block and the….Cylinder Heads! The engine block is a large chunky piece of metal, often iron, that contains the pistons and crankshaft. The cylinder head is a much smaller piece of metal, usually aluminum nowadays, that contains the combustion chambers and valves. There’s a ton of heat generated in these two, particularly in the head. If you remember your high school physics you’ll know that heat makes things expand, things like your block and heads, then they contract as they cool. This expansion and contraction causes there to be a little bit of movement between the heads and the block. In all modern engines that I’m aware of the gaskets have been engineered in such a way that this small amount of movement doesn’t have any effect on its’ ability to seal, though there were a few engines that had some real problems in the ‘90s.
Overheating is the biggest cause of head gasket failure. The engine block, being the more robust part and not having exhaust gasses routed through it, deals with this heat better than the heads. The heads can get so hot that they warp, expand to a point that they can’t return to their normal shape. When that happens there’ll be spots where the head gasket isn’t held as tightly as it needs to be and it will fail, leaking coolant, compression or both.
Sometimes the cause of failure will be corrosion. Poorly maintained coolant will allow corrosion to eat away at the head or block and eventually tunnel around the head gasket. A lot of times the owner is unaware of the problem until there’s enough of a coolant leak to overheat the engine. Then, see paragraph above.
The key to keeping this from happening to you is maintenance. If hoses are replaced before they fail they won’t blow out. If someone is keeping an eye on your radiator and water pump the chances of dramatic failure decrease. If your coolant is properly maintained it can’t erode your engine. We would like to provide that service to you.
From your Local Mechanic, All Tune and Lube Tempe. Complete Auto Repair and Maintenance.