2003 Ford F250 - Thread heads

I have a ford f-250 4x4 with the 5.4 engine and it has the aluminum heads. It has a problem where the spark plug thread is approximately 3/8” longer than the head thread, causing the carbon on the spark plug threads to eat the aluminum threads when you replace them and they get so worn they no longer hold the spark plugs. I know they can be Heli-coiled, but that is not a solution I am looking for. I also have a problem losing antifreeze (approximately ½ gal to a tank full. I don’t see any leaks, no smoke, no water in oil, no (noticeable) increase in oil etc, so I have no idea what else to look for to trace down the antifreeze leak.

I have several questions based on the previous information -

  1. Will a factory rebuilt engine or heads have updated heads that do not have the spark plug problem? (head question)
  2. Could it be a crack in the head exhaust port? (antifreeze question)
  3. Is there any product worth trying to stop the leak? (antifreeze question)
  4. If I replace the head gaskets should I replace the timing chain (118,000 mi)? (antifreeze question)

If the truck has an automatic transmission, check the tranny fluid for coolant contamination.

To remove the heads to replace the head gaskets requires removing the timing chains.


All the modular engines have aluminum heads

It’s the most common and widely-used solution. but usually only when a spark plug has been ejected from the head.

Probably not related to the spark plug issue. Check the oil and transmission fluid level. A failing head gasket can leak coolant that can end up in the oil pan. Likewise a transmission cooler can leak and coolant can get into the transmission.

You have the P.I. (Performance Improved) heads they have more threads for the spark plugs than the older (1997-1998) non- P.I. heads. Aftermarket heads may have an improved design though. However aftermarket heads for the 2 valve 5.4L, and will likely run several grand once you figure in the labor and cams.

You’d probably see white smoke or some evidence of a leak if that were the case.

It wouldn’t hurt, though the 2 valve 5.4L doesn’t have the reputation for timing chain issues that the VCT-equipped 3 valve 5.4L’s did.

I knew guys who raced 3’3 midgets with air cooled VW engines who Heli-coiled the engines as soon as they got them because it nade it that much easier to change plugs. I hated changing the plugs on my 71 VW Bus because it always felt like they were cross threaded but never were.

If you are going to change the plugs, take it slow, apply penetrating oil, when it binds, apply a little more oil turn them in a little and try to gain more ground and repeat. You will probably only have to do it once.

If you find out you need to take the heads off to change the gaskets before you change the plugs use a Dremel tool wire brush to de-carbon the threads.