Engine: Spark Plug Tube Seals

What it Does

Spark plug tube seals go between the engine’s spark plug tubes and the engine’s valve cover(s) so that engine oil cannot leak from the upper engine area into the spark plug tubes.

Why This Matters

Spark plug tube seal failure results in oil leakage and ignition system part contamination. This can encourage misfires to develop, have a minor impact on spark plug replacement costs, and increase service part costs due to oil contamination.

Possible Problems and Concerns

Oil Leakage (loss of sealing tension):

As these seals age, they can loose their resilience and fail to hold tight against the spark plug tube. This allows oil to leak from the upper engine area into the spark plug tube.

Oil Leakage (installation error):

If sufficient care is not taken during valve cover installation, a tube seal can bind on the top of its spark plug tube and tear or deform, resulting in severe leakage into the spark plug tube.

Oil Contamination:

Pooling of oil in the spark plug tube can damage boots for ignition coils and spark plug wires. It attacks the rubber boots. Since these boots insulate against electrical energy jumping away from the spark plug, degraded or destroyed boot condition can encourage an ignition system induced misfire.

Increased Service Cost:

During a spark plug replacement, if oil is found pooled in the spark plug tube, it must be removed prior to installing the new spark plug and will likely also need to be removed from the applicable ignition coil or spark plug wire boot. This increases the working time required for the spark plug replacement.

Valve Cover Damage:

The spark plug tube seal must seal to both the valve cover and the spark plug tube to prevent oil leakage. A mistake or lack of care during seal removal can result in scratch, nick, or gouge damage to the portion of the valve cover that seats and secures to the seal.

Recommended Parts Brands

Original equipment or comparable.

Repair Notes

Spark plug tube seals require valve cover removal for replacement. In many cases, they are round seals that install tightly in the valve cover itself. There are also designs in which they are incorporated into the valve cover gasket.