Hey guys a few days ago my 99 f150 5.4 blew a spark plug out of the number 2 cylinder. I changed them 20,000 miles ago with motorcraft platinum plugs and put them in with no anti seize and the engine was dead cold wasn't even cranked that morning and torqued them to 28 foot pounds. I was just wondering why it did that and what can I do to prevent it and do I have to worry about the other 7 blowing out? Also truck has 220,000 miles on it. Thanks in advance

 

I'd definitely re torque the other 7

 

Well, likely differential expansion between the steel plug and aluminum head caused the threads to loosen .

I once shot one on a toyota 3VZE, I could barely get the remaining ones out, so sometimes it just happens.

OR..you could have weakened the threads and differential expansion broke them and it stripped out. Or a previous owner could have.

Like brake bolts, doesnt hurt to put a check on them once in a while.

 

This^^^. Checking plugs for proper torque is routine maintenance on these engines, should have been put in the owners manual. Shame on Ford for that. And yeah, it's a common problem on all makes with aluminum heads. A buddy of mine has a 2000ish dodge 5.9 and it spit a plug once. Keeping them torqued is the only fix.

 

So what do yall think the limit is for when the spark plugs should really need to be changed

 

I'd say 40,000 to 50,000 miles.... but that's a personal preference.

 

Depends on plugs
At least 100000

My honda pilot has original iridium plugs at ......255,000 miles. Runs like a top.

 

I had the same problem on my '97 Expedition. I only had 105,000 on it. It scared the crap out of me when it blew. The motor was cold ( well it was sitting ) and when I cranked it, it blew. Had a shop fix it and never had another blow. Ford told me I had to buy a new head for $3200. WTH... I could almost buy a new motor for that price. Had it fixed for $250. Ran fine with no trouble.

 

Your the first ever, absolutely never heard of that happening after using the new spec. You did everything correctly. Only possibilities would be, accuracy of the torque wrench, which type and name brand did you use, and you sure you got it to 28' lbs. ? Other than that, the plug chamber is damaged from either a cross thread or missing threads from a loose plug occurrence in the past.

You can try adding more torque, but your pushing the plugs torque yield. You may separate the ceramic insulator seal from the metal housing/shell. It happens to most plug types when over torqued. When it does, the evidence will be a poor running engine and there will be carbon trails on the outside on the ceramic insulator.

So you take that chance if you go further than 28. Yea there wasn't an in-between when they came up with that number, just a max. Higher than that isn't the recommendation and that's due to plug yield ONLY. These heads can be torqued to 100' lbs without any damage occurring...it's been officially proven by experts in the field. It's the plugs you have to watch when cranking it up.

Check for damage in the chamber. If minimally damaged (what it may be if it was torqued correctly), use a thread sealer, but only on the top 4 threads. I'm not sure, but loctite quikstix blue may be good enough...better off to go with something specific to the task if can find it. That's just one idea. But yea, go over your work best you can and look for damage. Check wobble five threads in.

 

The threads was wiped out in that cylinder when I checked and I was using a snap on torque wrench and clicked all all of them twice