Valve stem seals prevent oil from contaminating the air/fuel mixture in the engine's combustion chamber. They also prevent intake and exhaust gases from contaminating the oil in the cylinder head and the rest of the engine. Valve stem seams are like any other round seal, only much smaller.

What happens when valve stem seals go bad?

When you have a bad valve seal, the oil that collects at the front cover of the head will end up burning when you push on the accelerator after coasting for a while. This is apparent especially when going downhill and again will be indicated by the excessive smoke that leaves the tailpipe.

How much does it cost to replace valve stem seals?

A valve stem seal replacement cost will vary. On average the cost will run between $900 to $1,800. The cost will depend on the make and model of the vehicle as well as where you take the vehicle.