Symptoms of a Failing Head Gasket

When motorists are experiencing car problems their mind churns through some of the worst-case scenarios. High on this list would be a blown head gasket. This article will explain what a head gasket is and review a handful of symptoms of one that has failed.

When it comes to problems with this component early detection is critical in preventing internal engine damage. This is magnified on aluminum engines since this type of metal doesn’t hold up to extreme temperatures well. In the end getting the answer to the question if the gasket has failed can be achieved with a few basic tests. When it comes to the diagnosis of this gasket no guessing is necessary because its failure creates clear evidence that can be evaluated by those who know what to look for.

The Head Gaskets Job

When you get down to it, this part is just a gasket. However, it’s one of the most complex sealing gaskets you’ll find in any engine. The part itself is usually of composite construction containing metal, fiberglass, Kevlar and sometimes carbon fiber. The gasket is compressed by a strategic network of head bolts to provide superior clamping force. It’s designed to handle temperature ranges from well below 0 to 3000 degrees Fahrenheit.

Although all of these things are daunting challenges to its survival the most stressful and critical is withstanding the internal pressure of combustion right after ignition. At this point the gasket could be exposed to pressures of 1000 psi or more. When a head gasket sealing capabilities are compromised by this sudden peak of pressure it pushes the gasket away from the combustion chamber. Mechanics and automotive enthusiasts have nicknamed this condition as a blown out head gasket. This is one colloquialism highly accurate in its description of the problem.

Blown Head Gasket Symptoms

Here is a quick explanation of why this one problem can produce a wide range of symptoms. The head gasket seals three major engine systems from each other. This is necessary as oil and coolant need to be passed between the engine block and the cylinder head. The head gasket seals these two systems and separates them from each other and keeps them away from the effects of the combustion chamber.

When the gasket fails it can open up in different ways creating different symptoms. As an example the gasket can deteriorate between the cooling and the oil passageways allowing pressurized coolant to flow into the engine oil system. This creates a milkshake like deposit on the oil fill cap or if severe enough it can be detected on the dipstick as it turns the oil into a jelly like slime.

Common Head Gasket Problems

One of the more common failures of the head gasket is for the compression seal to blow out a spot between the combustion chamber and a cooling passage. This allows compression to leak into the cooling system. If this condition is severe enough they can often be detected by looking for bubbles in the radiator or coolant system reservoir. Some professional auto repair shops that have emission test equipment can place the exhaust probe over the coolant to detect exhaust gases mixed with the anti-freeze.

As for the driver when this type of failure exists a common complaint would be intermittent overheating. This is because the engine cooling system is designed to be free of air pockets. A compression leak into the cooling system creates air pockets that stop the coolant from flowing freely.

When this situation is severe enough drivers might complain of the temperature needle swinging up quickly. If the air pockets created by the combustion leak work their way to the coolant reservoir and are vented to the atmosphere flow may resume and the temperature gauge returns to normal for a short time before the cycle begins again.

Positive Identification of Blown Head Gaskets

There are several rudimentary tests that can be performed when a blown head gasket is suspected. As mentioned throughout the article there is telltale signs that will push the mechanic to administer these tests and help them decide which one to perform. If a compression blowout is suspected each individual cylinder can be tested to see if it holds pressure. A mechanic needs to be on his toes when evaluating the results because a cylinder that will not hold pressure could be leaking from the intake or exhaust valves as well as the head gasket.

If combustion is suspected of leaking into the coolant system there is a low-cost combustion leak tester fluid that changes color when it detects trace amounts of exhaust gases. Remember that coolant shouldn’t have any post combustion gases in it. Although there are other reasons besides a compromised head gasket that would allow exhaust to mix with these fluids, gasket failure is the most common reason. Although cracked blocks and cylinder heads can also cause the Lisle test fluid to change colors. Rest assured, when a head gasket is suspected of failure, a skilled mechanic can confirm the condition prior to disassembling the engine.