Diagnosing and Fixing Valve Cover Gasket Leaks
A leaking valve cover gasket can cause a range of problems, from oil leaks and stains to catastrophic engine damage over time. Thankfully, with vigilance and some mechanical skills, valve cover gasket leaks can be promptly diagnosed and repaired. This article provides a comprehensive, step-by-step guide to identifying symptoms, understanding causes, diagnosing leaks, and correctly fixing valve cover gaskets in your vehicle.
Introduction
The valve cover is the metal housing that encloses the top of the cylinder head and protects the valve train components on modern internal combustion engines. Attached to the valve cover is a gasket made of rubber, cork, or other materials that provides a critical oil and air seal for the valve cover.
Over time, valve cover gaskets can become worn, brittle, or damaged. Cracks, shrinkage, or rotting of the gasket material allows oil to seep out from the valve cover, resulting in leaks. Valve cover gasket leaks should not be ignored, as the drips of oil can damage other engine components, lead to further oil leaks, and even cause engine overheating or fires. Replacing a worn valve cover gasket is a relatively straightforward repair that can prevent catastrophic engine failure down the line.
This article will teach you how to:
- Recognize common symptoms of a valve cover gasket leak
- Understand the potential causes of valve cover gasket leaks
- Diagnose a valve cover gasket leak correctly
- Step-by-step instructions for replacing a valve cover gasket
Let’s start by identifying the most common observable symptoms of a leaking valve cover gasket.
Symptoms of a Valve Cover Gasket Leak
The symptoms listed below can indicate a leaking valve cover gasket. The more symptoms you notice, the more likely it is that the gasket needs to be replaced:
Oil Leaks and Stains
The most obvious symptom is oil dripping directly from the valve cover gasket location. This will leave oil stains and residue around the valve cover. You may notice the leaks directly on top of the engine, but oil can also drip onto other engine components.
Burning Smell
Oil dripping onto hot engine components can produce a distinct burning smell from under the hood. Be aware of any unusual burning odors.
Misfires
If enough oil seeps into the spark plug wells, it can cause the plugs to misfire. This reduces engine performance.
Overheating Engine
Leaks can cause low oil levels over time, reducing crucial lubrication and cooling of engine components, leading to overheating.
White Smoke
Oil leaks reaching exhaust components can produce white/blue smoke from the tailpipe. This indicates oil is being burned in the combustion chambers.
What Causes Valve Cover Gasket Leaks
Before repairing a leaking valve cover gasket, it helps to understand what commonly causes the gaskets to fail in the first place.
The primary reasons valve cover gasket leaks occur include:
- Worn/aged gasket material – Gaskets naturally degrade and harden over time. As the gasket material loses flexibility, shrinking and cracking occur.
- Damage to the valve cover – The metal valve cover can become warped or cracked due to overtightening or heat cycles. This damages the gasket seal.
- Loose fasteners – If the bolts or screws securing the valve cover are loose, the gasket seal can fail. Missing fasteners also cause leaks.
- Oil contamination – Dirt and debris can prevent the gasket from sealing tightly against the cylinder head surface.
Being aware of these failure points can help you diagnose the leak accurately. Next we’ll cover how to systematically diagnose valve cover gasket leaks.
Diagnosing a Valve Cover Gasket Leak
Diagnosing a valve cover gasket leak involves three main inspection steps:
1. Visual Inspection
Pop the hood with the engine cooled and visually inspect the valve cover.
Look for:
- Oil residue/stains around valve cover
- Damaged/cracked valve cover
- Loose or missing fasteners
- Gasket protruding from valve cover seam
2. Feel for Oil Leaks
Gently feel around the valve cover gasket sealing surface with your fingers to find the exact leak location. Oil may still be wet/damp. Also inspect the cylinder head surface.
3. Check Engine Oil Level/Condition
Low oil levels over time can indicate a valve cover gasket leak. Inspect the oil color/quality and top off oil if running low.
These three inspection steps should locate valve cover gasket leaks accurately. If you confirm a leaking gasket, continue to the replacement procedure below. Consider replacing the valve cover itself if it is badly damaged.
Replacing a Leaking Valve Cover Gasket
Follow this 10 step procedure to safely replace a leaking valve cover gasket:
1. Disconnect negative battery terminal
Disconnect the negative battery cable to prevent electrical shorts.
2. Allow engine to cool
Make sure the engine is completely cooled to avoid burns. Recently running engines can remain hot for over an hour after turning off.
3. Remove accessories/components
Remove any brackets, hardware, hoses, or wiring that obstruct valve cover removal. Label items if necessary.
4. Clean valve cover
Use a gasket scraper and degreaser to thoroughly clean old sealant/grime from the valve cover and cylinder head surface.
5. Inspect sealing surfaces
Check that the sealing surfaces are clean and free of warped/damaged areas. Repair any flaws that could prevent gasket sealing.
6. Remove old gasket
If any old gasket material remains stuck, scrape gently with a gasket scraper or use a soft wire brush.
7. Install new gasket
Many replacement valve cover gaskets now feature self-adhesive backing for easy installation. Apply sealant if recommended by the manufacturer.
8. Reinstall valve cover
Carefully lower the valve cover back onto the cylinder head with the new gasket in place. Hand-thread fasteners first.
9. Tighten fasteners
Finally, tighten the valve cover bolts or screws to the torque specs listed in your repair manual using a calibrated torque wrench. Do not overtighten.
10. Reconnect components and battery
Once the valve cover is reinstalled, reconnect all accessories, components, and the negative battery cable.
Be aware that specific replacement procedures can vary across engine types and vehicles. Always refer to the factory service manual for your exact vehicle when conducting repairs.
Valve Cover Gasket Leak Symptoms – Video Review
Conclusion
Identifying and properly fixing valve cover gasket leaks is crucial preventative maintenance for your engine. Left unchecked, these leaks can lead to dismal outcomes like seized pistons, rod bearing failure, fires, and complete engine rebuilds. Monitoring your vehicle for telltale symptoms, understanding why gaskets fail, accurately diagnosing leaks, and conducting a step-by-step professional-quality repair using the guide above will help maximize engine life and avoid catastrophic damage from neglecting worn valve cover gaskets. With vigilance and dedication to vehicle care, valve cover gasket leaks can be effectively repaired before major issues occur.
Valve Cover Gasket Leak Troubleshooting
| Symptom Notice | Potential Cause | Corrective Action |
| Oil leaking from valve cover | Worn/damaged gasket <br> Warped/cracked cover <br> Loose/missing fasteners | Replace gasket <br> Replace/repair valve cover <br> Reinstall/replace fasteners |
| Burning plastic smell | Oil dripping on hot exhaust | Replace gasket <br> Clean oil residue from exhaust |
| White smoke from tailpipe | Oil leaking into combustion chamber | Replace gasket <br> Inspect piston rings/cylinders |
| Engine overheating | Low oil from leaks <br> Oil leaks on sensors | Top off oil <br> Clean sensors |
| Misfiring/loss of power | Oil fouling spark plugs | Replace gasket <br> Clean/replace plugs |
