If your car is leaking oil from the upper engine, it may be difficult to find the exact source. Oil often leaks down below the engine compartment and can then be blown around under the vehicle by wind as you drive. One very common source of a leak, however, is around the valve-cover gasket. Check for the presence of oil on top of the cylinder head and near the spark-plug connections. The rubber gasket sits beneath the valve cover -- the metal lid that sits on top of the cylinder head on most cars. The lid and gasket keep dust and debris out of the engine while keeping the oil in. It's not uncommon for the gasket on an older engine to develop a leak, and in most cases this problem is not serious. Replacing a leaky gasket is a relatively minor job, but it's definitely something that should be taken care of. Important: Check the service manual for your vehicle before tackling this job since there may be particular procedures unique to your specific vehicle. Also, you will need the proper torque specifications for reinstalling the valve cover. The basic steps are outlined below. Materials: Service manual for your vehicle
Socket wrench or speed wrench
Torque wrench
Rubber mallet
Gasket scraper
Gasket cleaner
Parts washer (optional)
Pliers - Allow the engine to cool before beginning work.
- For safety, disconnect the negative battery cable.
- Use pliers to detach the breather hose from the cover fitting by loosening the hose clamp (figure A). Tuck the hose back out of the way.
- Remove the spark-plug wires from their retaining brackets and move them aside so that they are out of the way (figure B).
- Use a socket wrench or speed wrench to loosen the cover bolts that hold the valve cover in place. Remove the bolts (figure C).
- Lift off the valve cover. If the cover does not come loose easily, tap it gently with a rubber mallet to free it from the engine head. Use caution since the valve cover is aluminum and can easily be damaged. Never force or pry the cover off. The old gasket should lift off with the cover. Be sure to remove the PVC valve and hose at the top of the cover and inspect these. They may need to be replaced also.
- With the valve cover removed, inspect the underside for buildup of carbon deposits (figure D). The amount of deposits gives an indication of how frequently the oil has been changed. Cars that have gone for longer intervals between oil changes will have a more serious buildup.
- With the cover off, use a scraper to clean away any carbon, debris or old-gasket residue from the top of the head around the seal (figure E). After scraping, follow up with a gasket cleaner. Be extremely careful when scraping and cleaning the area around the seal. If any residue or particles fall down into the head and inside the cam, the contaminants may cause internal engine damage.
Tip: Use a folded piece of paper or toweling to cover the valve-cover opening while cleaning the cylinder head to make certain no contaminants get inside the engine. - With the valve cover removed, the best way to clean it of carbon deposits and gasket-residue is with a parts washer (figure F). These use chemical cleaners and a rotating brush to help clean away stubborn deposits. If you don't have access to a parts washer, you can use soap and water. Remove the old gasket from the groove where it fits in the cover (figure G).
- Scrub away as much residue as possible from the underside of the cover (figure H). Be certain to clean around the PVC valve and grommet, or replace them if they are damaged. Do not scrape the underside of the cover as the aluminum can easily be gouged or damaged. After cleaning, let the cover dry completely.
- Once the cover has been thoroughly cleaned, seat the new gasket into its groove in the valve cover (figure I).
- With the gasket firmly in its groove, reinstall the cover onto the engine head using a torque wrench (figure J).
Important: Reinstalling the valve cover requires that the cover bolts be tightened back down to the proper torque specifications. Check the service manual for your vehicle to get these specs. - With the cover reinstalled and torqued to the proper specifications, reattach the plug wires and the breather hose.
- Reconnect the negative battery cable and start the engine. Run it for a few minutes and check to make certain there are no leaks.
The rear valve-cover gasket can be replaced following these same basic steps. It's farther back in the engine compartment and a little more difficult to access, but the procedure is much the same. The main difference is that you will need to carefully disconnect the oil temperature sensor (figure K) before removing the rear valve cover. Consult your vehicle service manual for specific information. Click here to download a PDF illustration showing the engine's valve-cover gasket.
Illustrations may be viewed by using 
RESOURCES :
The Complete Idiot's Guide to Trouble-Free Car Care
Author: Dan Ramsey
ISBN: 0028635833
Alpha Books
Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896
Automotive Parts Washer
Model: 660N
The Automotive Parts Washer
is available from
Safety Kleen Corp.
1000 N. Randall Rd.
Elgin, IL 60123
Toll-free: 800-699-5740
Web-site:
www.safety-kleen.com
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