Valve Cover Gasket

Reader Question: My valve cover gaskets continue to leak oil. I have had them three times in the last two years, and now they are leaking again. is this happening?

Dear Arnold,

Stopping an oil leak can sometimes frustrating if you don't find and correct the source of the problem. valve cover gaskets are probably just the symptom of the leak and the source.

First, you need to determine what kind "leak" your car has. There are two types of oil spills, a and a leak. A seep is just that, a slow seepage of oil that does produce a drip, is sometimes not noticeable on the pavement as "spill," and generally does not seep enough oil to affect the oil level between oil changes. You may sometimes notice or a burning odor caused by oil seeping on a hot engine or from into contact with hot exhaust parts. Seeps do not necessarily have to repaired immediately.

A leak is just that, a leak that causes drip of oil when the vehicle is parked. A leak will produce a puddle oil on the pavement, and continues to drip while the vehicle is driven. A leak can adversely affect oil levels, and if not checked, can enough oil to do internal engine damage. A leak will usually accompanied by smoke and a burning odor. Leaks should be immediately.

It is extremely common to have oil from a valve cover on just about every car with over 30,000 miles. small oil seep at the valve cover gasket will attract dust and dirt sticks to the seepage, so this "seep" can be obvious to naked eye and still not be serious enough to require replacement of gaskets at this time.

Just for grins, I went out and looked my car and my wife's car, and both vehicles have valve cover seeps. Although these seeps are coming from a leaking valve cover gasket, do not warrant replacing the gasket at this time. If one of my cars taken to a repair shop, I would suspect I would receive a call from service manager advising me my valve covers are leaking and should replaced. He would be correct to say they are "leaking," if I did not experience one of the symptoms of a leaking gasket described earlier I would not have the gaskets replaced at this time.

So why do the gaskets leak? The covers are located at the top of the motor and they are a common of engine oil seeps and leaks. The valve covers are just that, protecting covers over the valves and rocker arms at the top of engine. The valve covers are bolted to the top of the engine and a egg-carton-shaped gasket made of rubber or cork that seals the cover the engine. here for illustration.

Oil is pumped from the bottom of engine to the top of the engine to lubricate the valve train. This pools inside the valve cover as it slowly drips back inside the via "drain back holes" inside the cylinder head, then cycles up to the valve train again. On a V-8 or V-6 engine, the covers are at an angle, and the oil accumulates at the bottom of valve cover. The hot exhaust system is located directly below the cover, and a small amount of leaking oil that comes in contact these hot exhaust parts can produce smoke and a burning odor. build up due to lack of frequent oil changes can cause these drain holes to become restricted, slowing the drain back process. restriction causes the oil to accumulate in the valve cover longer exert more pressure on the valve cover gaskets.

A Positive Crankcase Ventilation (PCV) valve is inserted in the valve cover itself, and the purpose of valve is to act as a vent for excess pressure that accumulates the engine and valve cover areas. here for illustrations A restricted PCV valve can cause this pressure to find new avenues to vent, and an oil gasket or seal usually "blown out" to let this pressure escape. Think of PCV valve as the valve on top of an old time pressure cooker in kitchen. When the pressure inside reaches a certain point, the begins to shake from side-to-side and vent off excess steam. If valve is restricted, the steam will find another way to vent off pressure--by blowing the lid off the pot.

If you have a higher-mileage car and only experiencing seeps as explained above, then it is my to just keep an eye on the gaskets and replace them should the escalate to a true leak. Also, make sure you are following preventive maintenance of your vehicle. The PCV valve should be periodically, and the PCV system should be inspected to make sure restriction is present. I replace the PCV valve when I perform a tune on vehicles in my shop. The valve is inexpensive and easy to install. Changing the engine oil and filter often and inspecting the PCV are the best ways to prevent costly engine oil leaks.


Austin C Davis

Learn more about oil leaks and gaskets