Tech Stuff

Ford Triton spark thread repair

"I’ve got to let you know up front that a tune-up on your truck may cost up to $1,500.”

How do you think your customer will take it when you tell him that?

As you may already know, if the spark plugs break off in the cylinder heads of Ford’s Triton (three-valve) engines you may have to pull the cylinder heads to retrieve the broken parts.

The OEM spark plug shell is separate from the threaded portion. Photo by Bob Weber
<p>The OEM spark plug shell is separate from the threaded portion. Photo by Bob Weber</p>

Ford knows about the problem and issued a technical service bulletin about it. The TSB states: “Some 2004-2008 F-150, 2006-2008 Mark LT, 2005-2008 F-Super Duty, Expedition, and Navigator, with 5.4L 3-V engine; 2005-2008 Mustang, 2006-2008 Explorer, Mountaineer, and 2007-2008 Explorer Sport Trac with 4.6L 3-V engine; 2005-2008 F-Super Duty, 2006-2008 and F-Stripped Chassis, with 6.8L 3-V engine may experience difficulty with spark plug removal. This may cause damage to the spark plug and leave part of the spark plug in the cylinder head. Affected engine build dates are as follows: 5.4L 3-V and 6.8L 3-V before 10/9/07, 4.6L 3-V before 11/30/07.”

The threads on these extended reach spark plugs do not extend to the end of the spark plug holes in the heads. There is a shell that extends about an inch down the hole into the combustion chamber. A loop at the bottom of the shell forms the ground electrode.

Exploded view of the Triton spark plug.  Photo courtesy Lisle Corp.
<p>Exploded view of the Triton spark plug. Photo courtesy Lisle Corp.</p>

During engine operation, carbon builds up on the shell between it and the cylinder head. As the carbon cokes and hardens, this acts as a “locking agent,” preventing the shell from coming out of the cylinder head during spark plug removal.

Sometimes the shell stays behind while the rest of the spark plug breaks away. Sometimes, it’s worse and the porcelain insulator remains with the shell.

If the spark plugs cannot be fully removed, the solution can involve removal of the cylinder heads, with the spark plug pieces removed at the machine shop. That’s when it gets expensive... real expensive.

Tags: spark plugs 
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