Blown sparkplug on Ford's 5.4l engine


I’ve just had a sparkplug blow out of my 1998 Ford Expedition, 88,000 miles. Last night I did some searching on the internet and it seems like this is a big problem with this motor. It’s the rear plug, on the passenger side and nearly impossible to get to. It blew out the plug and destroyed the coil. The garage mechanics said it must be something from below, piston,valve that pushed it out. But from what I’ve learned, it’s a faulty design. They want to pull the motor and replace it with either a new long block or a junk yard motor, $4-5,000. This SUV is probably only worth $7-8,000 at best! They say that to just pull the head, the labor costs would be about the same to pull the motor.

Since this is a major problem with this motor, is there some kind of fix, other than a new or rebuilt motor? says they have some type of insert, that can be used without removing the head, for about $500.


Rich Franco

Here’s what I use to repair stripped out spark plug threads on these engines. Alot cheaper than removing the head!


Any decent shop should own one of these tools…A little grease applied to the tap will catch and hold any aluminum chips and keep them out of the engine.

Replace the entire engine?? Find a new repair shop. These guys are thieves.

It can be repaired as suggested and it’s not that major a problem. I’m of the opinion that the design is not so bad as the technique used in installing the plugs. The threads are shallow and the torque specs are fairly high. It seems to me the torque is around 15-17 Ft. Lbs depending on the source of the info.
This is way too high IMHO and if someone at the factory overtightened them a bit or if someone has replaced the plugs and grunted them down in the past then this could have caused the problem.
Another possibility is having the original plugs in place for a long time and when they’re removed some of the threads may be destroyed because the plug threads have galded to the ones in the head.

Find another shop. You don’t need an engine.

After looking on the internet and seeing how many of these 5.4ltr motors blow spark plugs, I am a little surprised that they didn’t suggest some of these ideas. The guy owns 3 shops here in Orlando and should know about this engine problem.
The master mechanic is really a straight shooter and when I stopped in, he asked about maybe there’s a self-tapping sparkplug. So he’s on my side. I’ll search for a plug like that. Thanks everybody and keep the ideas coming,

MILLIONS of these engines have been made and only a very small percentage have this problem. But even so, that number is in the thousands…

FORGET a “self-tapping” spark plug. They do not exist. The tool Tester described is specially made to install a “Heli-Coil”, a new set of steel threads, in the original hole. This is a permanent repair you can trust, stronger and more reliable than the original aluminum threads.

Piston or valve pushed it out? They better not have said that.

Many people like Timerserts or Bigserts better than the more commonly-recognized Helicoil. Like Helicoil, they have kits specific for these engines.

There is a possibility that the spark plug threads may be able to be repaired with a “Heli Coil” this is an aftermarket thread that is installed in the head where the threads have been pulled out. Check with a reputible machine shop or engine rebuilder. This can be done and is not engine or even head replacement many times but the right cylinder head usually has to come off to access it.

What I’ve learned so far is that the Heli coils don’t last as long as the “Timeserts” insets, any comments? I’m hoping I can repair this at my garage place without removing the head.

thats a very common problem with the 5.4 depending on how hard it is to get to a good mechanic can usually put a heli coil in the stripped hole i have done it before on an easy to get to plug its rely no big deal happens every day

If you want some specific advice for this engine, I suggest that you go to a board that deals with vehicles that have Ford modular motors. A Ford truck site would probably be worthwhile. I have seen lots of discussion of this at That would be 4.6 L, but substantially similar. Since access is an issue, and Expy board might well be most useful. I seem to recall that with Ford truck-based SUVs removing the body is easier than pulling the engine in some respects. From what I recall, if you have a little more than basic mechanical skills, you should be able to get an insert in there if you can get access.