Saturday, September 20, 2014 Detailed Auto Topics
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Change can sometimes be very useful.  Poorly thought out change can also be very costly, without providing benefit

In my opinion, the Ford two-piece spark plug is a perfect example of the later.  The multitude of people unlucky enough to own a vehicle with this plug may learn that the hardest way.

Suppose you decide to replace the spark plugs in your Ford three-valve V8 engine.  You buy the new spark plugs.  First you notice the strange appearance.  An extended base with a looped electrode.
This is the Ford two piece spark plug

Ford two piece spark plug prone to breakage

Piece one contains the porcelain insulator, hex base and threads.  Welded to the bottom is piece two, with the lower tip and electrode.  A very innovative looking device?   When you remove the first plug, you notice it looks very different.  Where’s the lower tip and electrode?  It’s seized in the cylinder and has broken away from the plug body.

New Ford plug on the left broken Ford plug on right

As you stare down the spark plug tube in the cylinder head your mind races.  There is no way to grab the broken part and the new plug will not screw in.  Welcome to Ford’s wonderful innovation, the two piece spark plug.  Sometimes all eight plugs may break.

Two piece Ford spark plug in three valve cylinder head

Ford is well aware of the problem, but has failed to issue a recall or warranty.  Instead they SELL an expensive and very time consuming set of tools to attempt to remove the broken parts. A set of pins are supplied, that are epoxied into the porcelain tip.  If this holds, a special puller is used to extract the porcelain tip.  This can take several attempts and several hours.

Broken Ford spark plug porcelain tip and extraction tool

Once the porcelain is extracted, a special tap is used to thread the metal electrode tip.  A small rubber plug is first placed in the tip to prevent metal shavings from falling into the cylinder.  Once threaded another special puller is used to extract the metal tip. 

One of the tools used to extract broken Ford spark plugs

If all goes well, you will be out a few hundred for the tools along with a weekend or more of effort.  If all does not go well, removing the engine and cylinder heads might be the other option.  

Ford engines that come with two-piece spark plugs

Ford 4.6L, 5.4L and 6.8L 3 Valve engines have the two piece spark plug; The 2 Valve engine does not use this plug
You can identify the two and three valve Ford engines by the valve cover shape


2005-2008 Mustang

2004-2008 F-150

2005-2008 Expedition, F-Super Duty

2006-2008 Explorer,

F-53 Motorhome Chassis

2007-2008 Explorer Sport Trac


2005-2008 Navigator

2006-2008 Mark LT


2006-2008 Mountaineer

Tips to avoid breaking Ford two-piece spark plugs

I have found, the sooner these plugs are replaced the better the chances of removal without breaking.  I like to replace them before 50,000 miles.

The engine needs to be cool when attempting removal.

Loosen the plug no more than 1/4 turn.  Stop and pour a small amount of carbon dissolving solvent into the plug tube.  Motorcraft offers chemical PM3.  Allow this to sit and hopefully loosen the carbon.

Tighten the plug and then loosen again, several times.  Do not apply more than 35 foot-pounds of torque trying to remove the plugs.

If the plug comes out, crank the engine several times to expel any liquid that could have entered the cylinder.

These plugs often snap off with little or no warning.  If you do not wish to attempt removal of the broken plug(s) tow the vehicle to a quality shop like AGCO.

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