The valve cover seals the top of the cylinder head; usually with a rubber or synthetic gasket that fits into a metal or plastic cover. The gasket is most often replaced when it begins to leak oil, or as a part of other engine work.
The valve cover doesn’t hold a reserve of oil like the oil pan, so oil leaks there tend to seep rather than drip. But being on the top of the engine does allow them to cause more problems.
Oil can leak from the valve cover onto the exhaust manifold, causing smoke and even fires, and it can coat and damage rubber parts.
Costs of Valve Cover Replacement
For some estimates of the valve cover gasket replacement cost, some common vehicles are used as examples using $100 an hour as a labor rate:
- For a 2004 GMC Sierra 1500 with a 5.3-liter engine, the labor time to replace either of the two valve cover gaskets is estimated at 0.7 of an hour. A factory replacement gasket set costs about $22 and a Felpro set costs about $17. The total cost to complete the job for either side would be about $92 using OE parts, and about $87 using aftermarket parts.
- For a 2015 Nissan Altima with a 2.5-liter engine, the labor time to replace the valve cover gasket is estimated at 1.3 hours. A factory gasket costs about $10, and an Apex gasket costs about $11. The total cost to complete the job would be about $140 using factory parts, or about $141 using aftermarket parts.
- For a 2005 Subaru Legacy with a 2.5-liter engine, the labor time to replace the valve cover gaskets is estimated at 0.9 for the right side and 1.1 hours for the left side. A factory valve cover gasket price is about $15, and a Beck/Arnley gasket set costs about $20. The total cost to complete the job would be about $105 for the right side and $125 for the left side using OE parts, or about $110 for the right side and $130 for the left side using aftermarket parts.
- For a 2010 Chevrolet Traverse with a 3.6-liter engine, the labor time to replace either valve cover gasket is about 3.5 hours each (access is very tight and obstructed for both). A factory gasket set costs about $46, and a Mahle gasket set costs about $48. The total cost to complete the job would be about $396 for either side using OE parts, and about $398 using aftermarket parts.
One thing to keep in mind is that usually, you can get individual valve cover gaskets from a dealer source. However, most aftermarket suppliers will bundle all the necessary parts together.
In addition to the gasket itself, there are often rubber grommets that seal the bolts holding the valve cover down and often seals that go around the spark plug tubes. As a rule, all of these should be replaced during a valve cover gasket replacement.
On a V-6 or V-8 engine, there will be two valve covers, and if only one is replaced, the unused parts from a set are usually given to the customer if asked.
Valve Cover Gasket Replacement
On some engines, the crankcase is fully sealed and under vacuum at idle and during normal operation. The valve cover gasket then also holds vacuum; a problem that causes an oil leak there under some conditions will cause a vacuum leak under other conditions, which can cause the engine to run poorly.
Replacement of the valve cover gasket involves moving out of the way whatever wiring harnesses or obstructions there are; sometimes removing coils or spark plug wires, then unbolting and removing the cover.
The surface of the cylinder head that the gasket seals against needs to be smooth and clean, Often, there are formed corners that the new gasket doesn’t seat against firmly. These are sealed with a small bead of gasket material which means cleaning off the old gasket material first.
What Else Might Go Wrong
The cylinder head has open passages to the crankcase, so the valve cover is essentially the upper seal for the crankcase. Any compression gases that escape past the piston rings (also called “blow-by) wind up in the crankcase. If there is an excess of this, the crankcase becomes pressurized and prone to forcing oil out.
In any case, where a valve cover gasket needs to be replaced, it is a good idea to take a quick check of an engine’s crankcase pressure. A new valve cover gasket might hold pressure on an engine with a blow-by problem, but oil will likely find another weak point to escape from.
The PCV system or the positive crankcase ventilation is designed to remove combustion gases from the crankcase and recycle them into the engine air intake. On a normal engine, this minimizes crankcase pressures and reduces any tendency to develop leaks.
If a valve cover gasket is leaking or if crankcase pressure is a suspect, it is a good idea to check the PCV valve. The PCV valve was at one time a regularly replaced service item as they were prone to clog and fail. However, newer engines run cleaner and problems are rarer.
Nevertheless, the PCV valve can still fail, and it should be ruled out as a cause of an oil leak problem during diagnosis or when repairs are being made. In many modern engines, the PCV valve is permanently built into the valve cover and only replaceable by replacing the valve cover.
If a valve cover is being removed in order to replace the gasket or other seals, it’s a good idea to verify that the PCV valve is functioning normally. If it’s not, the most economical time to replace the valve cover/PCV valve is when it is already removed.