Valve Cover Gasket Leak

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Reader Question

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

Arnold

 

Hey there Arnold,

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

First, you need to determine what kind of “leak” your car has.

There are two types of oil spills, a seep and a leak. A seep is just that, a slow seepage of oil that does not produce a drip, is sometimes not noticeable on the pavement as a “spill,” and generally does not seep enough oil to adversely affect the oil level between oil changes.

You may sometimes notice smoke or a burning odor caused by oil seeping on a hot engine or from coming into contact with hot exhaust parts. Seeps do not necessarily have to be repaired immediately.

A leak is just that, a leak that causes a drip of oil when the vehicle is parked. A leak will produce a puddle of 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 drain enough oil to do internal engine damage. A leak will usually be accompanied by smoke and a burning odor. Leaks should be corrected immediately.

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

Just for grins, I went out and looked at 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, they do not warrant replacing the gasket at this time.

If one of my cars were taken to a repair shop, I would suspect I would receive a call from the service manager advising me my valve covers are leaking and should be replaced. He would be correct to say they are “leaking,” but if I did not experience one of the symptoms of a leaking gasket I described earlier I would not have the gaskets replaced at this time.

So why do the gaskets leak?

The valve covers are located at the top of the motor and they are a common source of engine oil seeps and leaks. The valve covers are just that, protecting covers over the valves and rocker arms at the top of the engine.

The valve covers are bolted to the top of the engine and a large egg-carton-shaped gasket made of rubber or cork that seals the cover to the engine. Click here for illustration.

Oil is pumped from the bottom of the engine to the top of the engine to lubricate the valve train. This oil pools inside the valve cover as it slowly drips back inside the engine via “drain back holes” inside the cylinder head, then it
cycles up to the valve train again.

On a V-8 or V-6 engine, the valve covers are at an angle, and the oil accumulates at the bottom of the valve cover. The hot exhaust system is located directly below the valve cover, and a small amount of leaking oil that comes in contact with these hot exhaust parts can produce smoke and a burning odor.

Sludge build up due to lack of frequent oil changes can cause these drain back holes to become restricted, slowing the drain back process. This restriction causes the oil to accumulate in the valve cover longer and 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 this valve is to act as a vent for excess pressure that accumulates inside the engine and valve cover areas. Click here for illustrations

A restricted PCV valve can cause this excess pressure to find new avenues to vent, and an oil gasket or seal is usually “blown out” to let this pressure escape. Think of the PCV valve as the valve on top of an old time pressure cooker in your kitchen.

When the pressure inside reaches a certain point, the valve begins to shake from side-to-side and vent off excess steam. If this valve is restricted, the steam will find another way to vent off excess pressure–by blowing the lid off the pot.

If you have a higher-mileage car and are only experiencing seeps as explained above, then it is my recommendation to just keep an eye on the gaskets and replace them should the problem escalate to a true leak. Also, make sure you are following proper preventive maintenance of your vehicle.

The PCV valve should be replaced periodically, and the PCV system should be inspected to make sure no restriction is present. I replace the PCV valve when I perform a tune up on vehicles in my shop. The valve is inexpensive and easy to install.

Changing the engine oil and filter often and inspecting the PCV system
are the best ways to prevent costly engine oil leaks.

Blessings,

Austin Davis

12 Responses to Valve Cover Gasket Leak

  1. Austin Davis says:

    Valve cover gasket leaks are pretty common starting at around this mileage interval….although usually they just “seep” a little oil onto the engine which causes a burning smell and maybe a little smoke under the hood. If they are actually leaking/dripping oil then its time to replace them. I would expect to see oil on the driveway if they are leaking, but sometimes the leaking oil tends to accumulate on the engine itself and only really drips when you drive on the freeway and the wind blows it off the engine onto the ground.

    I would have a mechanic look into this farther, and will usually require the engine to be cleaned off so the source of the leak can be identified. There are many seals and gaskets on the engine that can leak and make it difficult sometimes to identify the source when everything is covered in oil. Any repair shop should be able to fix this for you, and probably cheaper and faster than the dealer would.

  2. Stephanie says:

    I have a 2008 Ford Fusion SEL with between 77,000-78,000 miles on it. The last time I took it to the dealership (Sticker on windshield states that it is due again this month or 81,000 miles)for my regular oil change they advised upon pickup that my valve cover were starting to leak. I checked my oil this morning & notice that it appears very low and I have recently (past day or so) noticed a burning oil smell. I see no visible leaks in any spots that i have parked my car in. Any suggestions?

  3. Austin Davis says:

    Not really Andy, replacement is what is needed…although I would take a wrench and “snug up” the mounting bolts first and see what happens. They have a tendency to loosen up over time and just a little tightening can work wonders

  4. Andy says:

    So I guess a can of oil leak stop would not really do much good for valve cover leaks?

  5. Austin Davis says:

    No probably not. The jerking could be a problem still with the transmission or it could be an engine miss, like from a bad spark plug or spark plug wire type of problem. I would take a wrench and LIGHTLY tighten up the valve cover gasket mounting bolts, which can loosen up over time and cause the gasket to leak. The noise, could just be low on P/S fluid.

  6. ericka says:

    i jus had my transmisson rebuilt on my 2002 ford focus n its makin lil jerks only goin 45mph n now makin a noise like the power steerings whinning noise wen accerlerating plus havrnt had an oil change n over 6000 miles n now i have oil on my valve cover gasket that i got replaced a yr n mth ago could n e of these resons b because of the jerkin

  7. Austin Davis says:

    Hi there. I have not heard of this EXACT problem on this EXACT vehicle, but have seen similar issues with oil leaking onto sensors (like the speed sensor) and causing problems. I have not worked enough on the older Optima’s to know how much money we are talking about to do the repair. if the repair is more than $300 I might suggest you get a second opinion.

    Any oil leaking on any sensor is not good for the sensor and can cause sensor failure though. I do agree that a bad speed sensor can cause transmission shifting and check engine light problems.

  8. Alisha says:

    Have a 2001 Kia Optima SE. Having problems with transmission shifting. Had car put on check engine light machine. Codes came back for Speed Sensors. Was told Pcv valve cover gasket and cam cover plate had to be replaced because oil was leaking onto speed sensors. Have you heard of or seen this problem before? And if so, what exactly do I need replaced?

  9. Austin Davis says:

    First thing I would do is put a wrench on all the valve cover mounting bolts and see if you can snug them down just a little…just a little, not too much. Those bolts can work loose and the gasket under the valve cover can get squished and become thinner over time.

    Then I would buy a can of CRC Brakleen from your local auto parts store and spray down the area around the valve covers to remove the oil that has spilled on the hot engine..producing the smell. The product drys instantly and is non flammable and uses no water.

    See how long those ideas last until you notice the smell again, or can see fresh oil leaking

  10. Carmen says:

    I was told that I have a really bad valve cover gasket leak last time I got an oil change, and I do sometimes smell a burning odor when I’m driving. From what you wrote, it would be considered a “seep” and not a leak (no puddles or variation in oil levels, etc.) A friend who knows about cars told me I don’t have to get it replaced, but the burning odor is new, and I wonder if that means I should replace it now. What do you think?

  11. Austin Davis says:

    Thank you, glad it was helpful to you.

  12. Matt says:

    Great info and suggestions!

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