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Stay up to date with the latest auto service newsWhen it comes to automobiles, things change often. As technology advances and we devise new and more efficient ways to make repairs, it is important to stay informed. These articles come from various sources, and we offer them here so that you can stay up to date on the latest happenings.
Ford's Spark Plug Woes
Starting in 1997 and extending thru 2008 Ford built three engines the 4.6 Liter, 5.4 L and 6.8 L all having the same design flaw. These engines have 2 valves per cylinder with aluminum cylinder heads. The problem that can occur is the spark plug (s) blowing out of the cylinder head and breaking the ignition coil belonging to the affected cylinder. Ford claimed it was because of improper torque being applied when the plugs were changed, but many times factory installed plugs have been known to blow out on low mileage vehicles. If you look at Fig. 1 about 5 threads actually hold the spark plug in the head, which is not enough in some instances to withstand the pressure of combustion. Not all engines fail with this issue but as they age the problems seem to occur more often, especially after a high mileage tune up is done. We feel this is because of the weakening of the aluminum threads when old plugs are removed. Ford only authorized cylinder head replacement when the vehicle was under warranty. There are several ways to repair the problem once a plug blows out but only one of them is authorized by Ford as the correct fix. Depending on the vehicle and the location of the blowout, Fords repair policy may require the cylinder head to be removed. All repairs require an insert being used which replaces the threaded area to maintain and hold the replacement plug. If the decision is made to not use their procedure another failure can occur making the problem worse so depending on customer circumstances and vehicle mileage all factors must be weighed as to which repair is used.
A second design flaw began in 2004 and extended thru 2008.5 year models. These engines are the 3 valves per cylinder (Triton) in the same displacements as above. The new style plugs used in these engines are of a two piece welded design as seen in Fig. 2. A very narrow space between the portion of the plug some in the repair industry call the bullet and the cylinder head will build up with carbon causing the plug to seize. If procedures are not followed before removal is attempted (even doing these things) sometimes the plug will break off at the welded area leaving the outer casing, porcelain insulator and center electrode in the hole. To remove this broken piece most repair facilities purchase an aftermarket set of tools which requires the technician to drive the porcelain downward in order to install another tool that will be used to remove the broken portion. If the porcelain breaks and falls into the cylinder all of this broken material must be removed and this is very difficult. The debris can cause internal engine damage. The cylinder head should be removed if there is any doubt that all the debris have been removed and this is very costly. One manufacturer offers a redesigned plug that has a one piece body that won’t come apart. We prefer to use these when replacing them.