Valve stem oil seals control how much oil reaches the valve guides. A small amount of oil lubricates the stem, but too much is drawn into the combustion chamber and burned. As seals harden and wear with age and heat, oil consumption and smoke can increase.
Common Symptoms
- A puff of blue smoke at startup after the engine has been sitting, which then clears.
- Blue smoke after long periods of idling or when decelerating.
- Increased oil consumption and oil-fouled spark plugs.
Valve Seals or Piston Rings?
Worn piston rings also cause oil burning, but they usually produce smoke under load and acceleration, together with low compression or high crankcase pressure. A compression test and leak-down test help separate the two. Worn valve guides can produce the same symptoms as seals, so guide clearance should be checked if the head is removed.
Replacement
- Seals can be replaced with the head on the engine on many applications, using air pressure in the cylinder to hold the valves closed, or with the head removed during a rebuild.
- Use the correct seal type for the engine. Intake and exhaust seals can be different.
- Protect the new seal during installation with the installation sleeve, and use the correct installer so the seal sits square on the guide.
- Check valve guide wear. A new seal will not stop oil consumption through a badly worn guide.
Evergreen Valve Stem Seals
Evergreen supplies valve stem oil seals as part of gasket sets and seals, and many Evergreen head gasket sets include them. Find the right part in the Evergreen eCatalog.
