Engine Gaskets: the Good, the Bad, the Ugly

Learn about engine gaskets and a few of their failings

Gaskets. How can these relatively inexpensive, somewhat simple vehicle components perform such a crucial role, stand up to torturous temperature and pressure extremes, and wreak so much wallet-emptying havoc if and when they do fail? As it is with most vehicle systems, the answer lies in physics and mechanical engineering.

What they are supposed do

Even two finely-machined, glassy-smooth pieces of aircraft-grade metal will have surface irregularities that won't allow a perfect seal when the parts are bolted together under pressure.

Whether it’s the head gasket on a 1993 Oldsmobile Cutlass Supreme or the gasket on the end of a garden hose, gaskets – when they work properly – are supposed to form an impenetrable seal between two surfaces, thereby preventing fluids or gases from mixing or escaping. Your vehicle literally has hundreds of gaskets, from the seal around the doors and windows keeping air and water out, to the gaskets on the thermostat housing, valve cover, head, intake, exhaust, and numerous other places.

Gaskets are supposed to be designed and manufactured to withstand contact with a variety of chemicals and tolerate temperature extremes without degrading or suffering any loss of performance, even with long-term use. They’re also designed to compress under pressure so that the gasket molds itself to and matches any imperfections in the surfaces being sealed. And, thanks to being engineered to exact specifications, they help ensure that they are an appropriate match to the surface being sealed and that the materials they’re constructed from can withstand the physical forces they’re exposed to, including pressure and temperature.

Spectacular failures

Despite, however, the best intentions and designs, gaskets can and do go bad. When they do, the results are often spectacular, and very expensive to correct. One need only look to certain Subaru models and years, the third generation of GM’s 60-degree engine, or the V-6s in several Toyotas to see the ugly picture gasket failure paints.

Head gaskets are one of the costliest gasket failures. Since those are the gaskets most drivers have heard about, and because most heavy DIYers know all too well the frustration and time commitment they demand, the reasons for gasket failure can be narrowed down to several of the most common.

• Engine overheating
• Deficient gasket design
• Detonation damage
• Improper torque

Some Subaru years and models are known for having head gasket issues, as are vehicles from some other manufacturers.

While some will debate whether the problem has ever actually been fixed, head gasket problems are no stranger to Subaru’s first-generation 2.5-liter engine found in many Imprezas, Outbacks, Legacy GTs, and Foresters around the ’96 to ’99 model years. The gasket in question here was a multi-layer one constructed of steel and coated with a graphite-type material. That coating can wear away over time as a result of contact with chemicals in vehicle fluids, and lead to a failed seal that allows coolant to seep into the combustion chamber.

GM’s problems with leaking intake manifold gaskets on the third generation of their 60-degree engine stretched from about the mid-90s to 2003 and led to several class-action lawsuits. Blame here was placed on the gaskets’ design and materials used that allowed the gasket to soften and lose its seal over time.

Toyota’s head gasket failures in the mid-90s on some of their 3.0 and 3.4 liter V-6s meanwhile were traced to the heads’ design and the fact that they are difficult to seal.

Ford Windstars, Dodge Neons, and many other manufacturers and models also experienced head gasket problems at one time or another, further illustrating the critically important role this vehicle component plays and the engineering challenges it presents.

What they’re made of

Depending on their application, gaskets are made of anything from cork, to metal, to rubber and beyond. Vehicle head gaskets are typically:

• Layered steel – constructed from multiple layers of steel (MLS) and usually coated to further enhance their performance. They’re the type most often used in vehicles.
• Copper – delivers a long-lasting performance for extremely durable gaskets. Copper is crushable and can conform under pressure.
• Composites – made from several materials, including possibly asbestos in some older applications, and usually considered a technology that’s less reliable and more commonly found on earlier vehicles. Composite or cork gaskets can be found in assemblies that aren't fastened with a great deal of torque, such as valve covers, thermostats or water pumps.

Don’t Blow a Gasket

A sure-fire way to avoid the time and expense of a head-gasket failure and subsequent replacement is to stay away from vehicles with known head-gasket issues that haven’t had the problem repaired or resolved. After that comes careful attention to changing vehicle coolant and oil at recommended intervals to prevent prolonged gasket exposure to chemicals that may hasten its degradation; using the vehicle manufacturer-recommended coolant; maintaining proper torque on the head bolts; and watching for early signs of gasket failure, including white exhaust smoke or coolant mixing with oil, to prevent further engine damage. White exhaust smoke is actually steam as the coolant is being burned off in the combustion chambers, and will usually have a strong antifreeze smell.

Learn more about blown gaskets here. 

Replacement

The head gasket itself isn’t expensive, costing only about $20 for a 1995 F150 with a 5.0-liter engine or $50 for the complete head gasket set. It’s the time that’s involved with replacing the head gasket that really ratchets up the expense ratio. There are a lot of parts and assemblies that will have to be removed before the head itself can be removed, giving you access to the gasket, and on a V-style engine both gaskets will need to be replaced. On a high-mileage engine, a blown head gasket can also mean other problems; it's not uncommon for an engine that's had the head gasket replace to start burning oil next, as the sudden change in compression can cause blowby at the rings.

Because head gasket repairs are easily over $1,000 and can climb another thousand or more beyond that, seek advice from a professional mechanic as well as a second opinion before committing to a head-gasket replacement. Depending on the problem, it’s also worth trying one of the numerous head gasket sealant products available to see if that brings temporary or even long-term relief.

Whatever the gasket problem, and fix, turn out to be, don’t blow a gasket because of the expense and frustration involved. It’s just another part of the joy and pain equation that is vehicle ownership.

Editor’s note: If repairing a blown head gasket is your next project, stop by Advance Auto Parts for the parts and tools you need to fix the problem. Buy online, pick up in store, in 30 minutes.