Distributors are an ignition system component found on many older cars and trucks. While they have largely been replaced by the development of coil on plug ignition systems, they are still commonly found on many vehicles made in the last few decades. They use a rotating shaft that is driven by the engine to distribute the spark to the engine's individual cylinders. As they are a moving component that can be removed, they require a seal just the same as any other engine component.
Distributors commonly employ a specifically sized o-ring that fits on the distributors shaft to seal it with the engine referred to as the distributor o-ring. The distributor o-ring simply seals the distributor housing with the engine to prevent oil leaks at the base of the distributor. When the o-ring fails it can cause oil leaks from the base of distributor, which can lead to other problems. Usually a bad or failing distributor o-ring will produce a few symptoms that can alert the driver of a potential problem that should be serviced.
Oil leaks around the engine
Oil leaks are by far the most common symptom of a failed distributor o-ring. If the distributor o-ring wears out or fails, it will no longer be able to properly seal the distributor with the engine. This will cause oil to leak from the base of the distributor and onto the engine. This problem will not only create a mess in the engine bay, but it will also slowly reduce the oil level of the engine, which if allowed to drop low enough, can put the engine at risk of receiving damage.
Engine performance issues
Another much less common symptom of a bad distributor o-ring is engine performance issues. If a bad distributor o-ring allows oil to leak onto certain parts of the engine bay, the oil may find its way into wiring and hoses, which can cause them to deteriorate. Deteriorated wiring and hoses can cause all sorts of issues ranging from vacuum leaks, to wiring shorts, which can then lead to performance issues such as reduced power, acceleration, and fuel economy.
The distributor o-ring is a simple but important seal that is found on virtually all vehicles equipped with a distributor. When they fail, oil leaks can form and develop into other issues. If you find that your distributor o-ring is leaking, have the vehicle inspected by a professional technician, such as one from YourMechanic. They will be able to look over the car and determine if you need a distributor o-ring replacement.