Oil leaks are a problem with older engines. Among oil leaks, valve cover leaks are the most common oil leaks that occur. Fortunately, valve cover gasket leaks are common. Most people do not worry about this problem much since it is very typical once a car ages and has some mileage.
Keep reading to find out what causes a valve cover to leak, symptoms of a bad valve cover gasket, and what to expect to pay to replace it (it will likely be more than you think).
What is a Valve Cover Gasket?
An internal combustion engine is an arrangement of many structural components assembled to work together seamlessly. Even so, these components must be sealed together to prevent fluid loss while an engine is operating.
The seal is achieved through the use of specialized gaskets that have been cut or molded for proper fitment. Traditionally, gaskets of this type were made from pressed fiber or cork material of varying thickness.
Today, the majority of automotive gaskets are made of rubber-coated plastic or specialty fiberglass-based products.
One of the structural junctions that we routinely use a gasket on, is that of an engine’s cylinder head(s) and valve cover gasket(s). An inline engine would have one cylinder head, while a “V” engine would have two heads.
These heads contain the valvetrain components (valves, valve springs, and rockers) that move back and forth continually to manage the amount of intake air drawn into the engine’s cylinder(s) and exhaust gases released into the exhaust tract.
These valvetrain components are constantly cooled and lubricated by an oil supply from the engine.
Every cylinder head has a valve cover (often referred to as a rocker cover in service literature of years past) bolted to it.
A valve cover provides a means of containing oil from leaking from the cylinder head on which it is mounted while preventing debris from entering the cylinder head area.
A valve cover gasket is located between each cylinder head and valve cover provides a more efficient seal than metal to metal mounting.
Without a valve cover gasket, oil would easily leak from the junction between these two components.
Signs of a bad Valve Cover Gasket
A bad valve cover gasket produces several concerning, yet recognizable, symptoms. Unless you own one particular model of engine, most variants of these symptoms remain relatively standard.
Below are some of the most common signs of a bad valve cover gasket.
#1. Smell Of Burning Oil.
When the oil begins to seep through a vehicle’s valve cover gasket, it will find its way to many heated surfaces. It is the oily residue that begins to “cook” when exposed to the various heat sources in a vehicle’s engine bay. This results in a perceptible odor of burnt oil.
This odor will remain until the offending valve cover gasket is replaced. Once the valve cover gasket has been replaced, the engine should be cleaned with degreaser and warm water to eliminate the above-mentioned odor.
#2. Oil On External Surfaces Of Engine.
The most recognizable sign of a leaking valve cover gasket is the oily residue coating the external surfaces of the engine’s cylinder head. If the leak is severe enough, the oil continues to leak downward and coats the engine’s block.
Oil not only creates a mess, it also makes it difficult to see the source of other potential leaks. This oil contamination can only be cleaned up once the offending valve cover gasket is replaced and the engine is thoroughly cleaned.
Although the oil that makes it to the undercarriage of a vehicle may be from the valve cover, it may also be a bad oil pan gasket.
#3. Low Engine Oil.
An internal combustion engine is designed to operate with a specific amount of motor oil, otherwise known as the total oil capacity of the engine.
When there is a leak from an engine, if oil is not replenished, the maximum total is reduced.
If a valve cover gasket leak is significant enough, it might reduce an engine’s oil level to a point that other secondary effects arise, such as the more rapid wear of internal parts.
In other words, it could be a real problem if it is not fixed fairly quickly.
#4. Engine Misfire.
Valve cover gasket leaks can allow engine oil to leak into many places which it is never supposed to be. For instance; an engine’s spark plug wells.
When engine oil begins to fill up, you can easily have many issues related to, what is most easily recognized, is engine misfire.
With enough time and enough leakage, you can contaminate a spark plug to the point of saturating its insulator and electrode. If enough oil seeps into the combustion chamber, it can even foul the spark plug altogether.
You may have to replace the spark plug, over and over and over again; unless you do eventually fix the engine’s leaking valve cover gasket.
Reasons Why a Valve Cover Gasket Can Fail
Although all valve cover gaskets are vulnerable to leak with time, there are several different reasons that can contribute to the degradation of a gasket’s structural integrity. Most of which, are at least partially maintenance-related.
#1. Infrequent Oil Changes.
Arguably, the leading cause of premature valve cover gasket failure is infrequent engine maintenance. Fresh engine oil, changed at a scheduled interval, contains a variety of additives that are intended to prevent gasket degradation.
These additives will break down over time, leaving an engine’s valve cover gasket(s) susceptible to accelerated wear, degradation, and aging. This situation tends to occur when routine maintenance items are ignored for extended periods.
#2. Overheating.
Another major culprit for valve cover gasket failure is overheating. Every engine is designed to operate under specific temperatures.
When an engine exceeds that temperature, as in the case of overheating, it can subject an engine’s gaskets to heat stress and substantially increase the likelihood of gasket blowout and cracking.
Overheating can not only destroy an engine’s valve cover gasket(s), but can also compromise the integrity of other critical seals, such as the head gasket. In the case of excessive engine overheating, it is not uncommon to find several failed gaskets on the same engine.
#3. Valve Cover Bolts Over/Under Tightened.
In addition, simply replacing a valve cover gasket will often yield leaking gaskets in short order when the valve cover bolts are not torqued properly upon installation.
Over-tightening these bolts can lead to pinched surface and/or improper gasket seating. Conversely, if the bolts are under-tightened, there may never be a sufficient seal between the metallic surfaces at all.
Is a Valve Cover Gasket Leak Serious?
In most cases, a valve cover gasket leak is not considered serious, particularly if the leak is minor and does not significantly contaminate the engine’s external surfaces.
Typically, a valve cover gasket leak is only considered serious if it becomes bad enough to cause major oil loss.
What is also worrisome is a valve cover gasket leak that bestows a misfire condition. This happens when oil from the leak runs off and finds its way into a spark plug well, which consequently contaminates a spark plugs electrode and insulator.
In any event, it is ideal to replace a leaking valve cover gasket within a reasonable amount of time. A leak like this will only get worse, thus leading to a severity that is consistent with both above examples.
Being proactive about repairs like this leads to the least chance of causing drivability-related symptoms.
How Long Should the Gasket Last?
The life expectancy of a valve cover gasket(s) in an engine is often based on a number of factors, such as the make and model of the engine, the frequency of routine engine maintenance, and any motorist’s driving habits.
Some OEM gaskets will be naturally better than others and therefore will offer a longer service life, while valve cover gaskets in a consistently well-maintained engine, will always be more likely to last longer than that of a neglected engine.
Another interesting fact about engine gaskets is that those found in a vehicle’s engine that are driven infrequently are more susceptible to failing sooner, as they become dry and brittle, just from resting.
But, on average, you can expect to get approximately 40,000-60,000 miles out of your engine’s valve cover gaskets, and that should be with little to no issues. In fact, in some cases, gaskets like these last a significantly longer time.
Valve Cover Gasket Replacement Cost
The cost to replace a valve cover gasket is typically different from vehicle to vehicle, often due to differences in labor cost associated with doing this type of job. There is a difference in the amount of labor required to complete the job depending on the engine design.
In many cases, a valve cover gasket replacement can be done in 1-2 hours. This means you can expect to incur a minor labor charge.
It’s not always the case, however. For some engines, it may take 4-5 hours to do this job, and the labor cost is going to be substantially higher.
Valve cover gaskets themselves can also vary in cost depending on the vehicle. Some valve cover gaskets may run as low as $15, while others can cost over $100. Take the cost of the valve cover gaskets into consideration, as well.
However, if you are looking for an average, you should expect to pay between $90-$400 for your valve cover gasket replacement.
The lower end of that range will always reflect a replacement on a 4-cylinder domestic engine, and the higher end of the range will reflect replacement on a foreign vehicle with a “V” configuration engine.
Valve Cover Gasket Materials
Valve cover gaskets all have one job (to seal properly to prevent oil leaks), but their make-up determines how well they do it. Below are some of the more common types of materials used for valve cover gaskets.
Plastic
Plastic valve cover gaskets have become more common (and popular) with the recent surge in “plastic” valve covers (common in modern vehicles). They are lightweight, fairly durable, and have some thermal resistance.
Plastic valve cover gaskets may not be suitable for older engines used in higher operating temperatures, as they tend to deteriorate quickly in extreme heat.
Rubber
Rubber valve cover gaskets made from silicone or nitrile rubber offer the best thermal resistance and longevity.
While not as durable as a plastic cover, they are better than cork and offer many temperature variations without changing shape and risking a leak. In general, rubber and silicone gaskets are relatively higher in cost than other gaskets.
Cork
Cork has been a traditional material for valve cover gaskets due to its lower cost and easy installation. Cork provides reasonable sealing for most engines, but it isn’t as good as rubber or plastic gaskets and probably not as durable.
Cork valve cover gaskets tend to compress only over time and can easily be replaced and filled more often, and could fall short in high temperature applications.
Metal
Metal gaskets are typically manufactured from aluminum or steel, offer some excellent durability, and are easy to seal in higher temperatures. But metal valve covers are generally more expensive and more difficult to install than most other materials.
FAQs.
Can a Leaking Valve Cover Gasket Cause a Fire?
Yes, a leaking valve cover gasket can cause a fire, but it’s a rare scenario. When oil leaks from the valve cover to the engine’s exterior, it may make contact with hot engine components, such as the exhaust manifold or exhaust piping, that are hot enough to ignite any oil drop that makes contact.
If you do smell a burning smell or see some smoke coming from under the hood you should address that immediately.
Is it Safe to Drive with a Leaking Valve Cover Gasket?
Generally, it is not safe to drive with a leaking valve cover gasket. The simple reason is because until you realize that you have a leak you might drive some distance with a low engine oil level which will lead to engine damage from lack of oil and the excessive friction and heat that occurs with insufficient lubrication between moving engine parts.
Why is My Valve Cover Gasket Leaking Just After Replacement?
If your valve cover gasket is leaking not long after replacement you are not the only one. The best and most straightforward reason is that the valve cover gasket was not installed properly, was pinched, or was damaged during the installation.
In a small number of cases there may be an issue with the valve cover itself being warped or cracked that is allowing oil to leak. To a lesser extent, a problem with the engine’s vacuum or pressure system could be causing the leak even with a new valve cover gasket installed.