Changed spark plugs in the 2007 5.4 today (140k miles).

[07navi]

The original plugs in 2004 to 2008 were prone to breaking but I ran 2 cans of Seafoam in 1/4 tank hard for a week and then cracked them open a bit and added some Liquid Wrench to the holes where the plugs were, let it sit for and hour and took them out without breaking any. I had to use the breaker bar on a couple of them and IDK how long they were in there but they had .080 gap.
The rear passenger hole is not that bad to get to if you bunji cord everything out of the way (shown). These were PZH 14F Motorcraft and the unbreakable newer ones are # 546.

 

[f150dave2002]

You definitely got the lifetime plus 50% on those. Great work and cheers for successful maintenance accomplishment. I only broke one when I did them.


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[07navi]

You definitely got the lifetime plus 50% on those. Great work and cheers for successful maintenance accomplishment. I only broke one when I did them.


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I bought the truck earlier this year, I don't let things go that long. I will probably change them again in 30k miles. I changed the brake, transmission, power steering, transfer case, and antifreeze fluid plus engine oil soon after I bought it. It really moves with the new plugs!

 

[Roger Phillips]

I change mine every 35k. I’ve got over 500k on mine.... the only other bad design issue I’ve had is the timing chain guides...they’re plastic... last time I replaced them I purchased the racing ones designed for the Mustang they’re aluminum

 

[Brent Harward]

Delighted to see your post! I advocate changing the plugs on the 5.4 sooner rather than later. Conditions vary so a hard rule is difficult to find. But generally if they're changed out under 90K miles the mileage AND performance is night and day different. BTW~That plastic "T" radiator connection in your photo goes out a lot. I replaced mine with a T and new hose clamps. The factory setup is about $150 for hoses and such that you don't normally need. JS

 

[07navi]

I change mine every 35k. I’ve got over 500k on mine.... the only other bad design issue I’ve had is the timing chain guides...they’re plastic... last time I replaced them I purchased the racing ones designed for the Mustang they’re aluminum

I think they make them plastic because they are quieter, don't leave metal debris in the system, and wear well. My v-10 guides looked so good a 200k miles I left them in and gave the new ones away when I sold it. Loose, slapping chains are what breaks them apart. Also, worn plugs are harder on the coils, plus they start wearing out from day one and people don't realize their MPG's and HP are slowly dwindling.

 

[07navi]

Delighted to see your post! I advocate changing the plugs on the 5.4 sooner rather than later. Conditions vary so a hard rule is difficult to find. But generally if they're changed out under 90K miles the mileage AND performance is night and day different. BTW~That plastic "T" radiator connection in your photo goes out a lot. I replaced mine with a T and new hose clamps. The factory setup is about $150 for hoses and such that you don't normally need. JS

I saw a couple quotes of $100 for the hoses from the stealer but they may have gone up since then. That hardware store 3/4" tee fix is fine if that's all that is wrong with them. Some people make up the entire system from local parts. I have seen 3 to 5 hundred dollars fees to fix them with the OEM parts.