Valve stem seal replacement
Valve stem seals prevent oil from travelling down the valve stem from the cylinder head into the combustion chamber.
Symptoms
- Blue smoke on startup after parking and when revving.
- Oil consumption rises while compression stays normal.
What's included
- When the rubber hardens and cracks, a recognisable symptom appears: blue-grey smoke on starting after parking and when revving, with rising oil consumption despite normal compression. This distinction matters: worn rings reduce compression, while faulty stem seals leave it normal, and this helps us distinguish the repairs. On many engines, replacement is possible without removing the cylinder head, making it substantially less expensive. We also inspect the guides: a worn guide quickly damages a new seal.
Why it matters
Worn rings drop compression, worn seals don't — that's exactly how the two repairs are told apart. A worn-out guide wears through a new seal within a few thousand kilometers.
More details
Valve stem seals stop oil from the head reaching the combustion chamber along the valve stem. When the rubber hardens and cracks, a recognizable symptom appears: blue smoke on startup after the car has been parked and on throttle blips, while oil consumption rises with normal compression. This is an important distinction — worn rings drop compression, worn seals don't, and that's exactly how we tell the two repairs apart. On many engines the seals can be replaced without removing the head, which is significantly cheaper. At the same time we inspect the valve guides: a worn guide kills a new seal within a few thousand kilometers.
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