5.4L plugs will not thread in fully
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New User
Joined: Dec 2008
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5.4L plugs will not thread in fully
I changed my spark plugs in my 97 Expedition and the new plugs do not thread all the way in. The old plugs were the factory original with the short reach threads. The reach on the new plugs is almost twice as long. I have read about the "blow out" problem some people have had and i think the reach was increased to help with this issue. The new plugs have about 11 turns of thread, but they will only thread in 5 turns until the stop hard. I am guessing the the head has a carbon build up were the old short reach plugs stopped, not allowing the long reach plugs from threading all the way in. Has anyone had this problem before? I am thinking of running a tap down the bore to clean out the carbon. Any thoughts or suggestion would be much appreaciated. This my first time on the group, so be gental...........Thanks
Jay
Jay
Tuned
Joined: Aug 2007
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The Motorcraft plugs I put in had the same throw as the originals in my 98 4.6 and 2003 5.4. Could be you have the wrong plugs. The reason they stop, before seating properly, is they hit something, maybe carbon build up but the top of the piston - not sure if it would be that bad and would not be on all 8, just 1.
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I cross refrenced the plugs on the web, every site that I checked says that they are the right plug. They are Boch 2X Platimum part #4304. I am going to the local Ford dealer today to see what the have. The guy at the parts counter is very helpfull, maybe they have some new-old stock with the short reach threads. I will keep the post updated.....jay
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Checked with the local dealer today. Ford has revised the plug application a few times since the truck was built. The revised Motocraft plug is a long reach thread. Time to break out the tapand die set! The parts counter guy thinks the heads have a carbon build up, I agree. The thread is 14MM. Does anyone know the pitch? Thanks for your support, this is a great group...........jay
Cross-Country
Joined: Jul 2007
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They are in as far as they are going. The extended threads will not turn down any more than the old plugs. The extra threads only help with the newer heads. The seating area is the same for both styles.
If it screwed down further it would hit the piston and valve.
If it screwed down further it would hit the piston and valve.
Postmaster
Joined: Oct 2006
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From: SE Texas
The heads use a 14mm .708 reach tapered seat plug. BOTH of the plugs,the old and the new style are exactly that. Your new plugs are not going to thread in any more turns than the old plugs did-the heads didn't magically get more threads when you removed the plugs.
JL
