Like so many others I had the pleasure of experiencing a blown plug at highway speeds puling a boat 400 miles from home, this April 04'. I was fortunate for the warranty.

What has come about with this situation? Recall. Service bulletin.

I'm new here, can you guys direct me in the right direction.

This site looks neato.

 

Welcome !! I am quite proud of the site too.

You can perform a search using "blown plug" and find all the skinny. I've installing the updated heads with more threads when a big cert won't work. It's common for the bank 1 heads to blow out. I've seen #2 and #4 more than other cylinders. I would be interested in seeing what an engineer could find, specifically failure analysis. I see #4 caused by leaking heater hoses and technicians inexperience in installing the hard to reach plug. As far as I know, the only fix that Ford has come across is more threads in the head and I think I've seen an updated plug mentioned with a full thread.

Anyone else know of a full thread motorcraft plug?

 

My guestimation of how it happens.

Since there aren't but three or four threads holding the plug in, and that they go in at an angle, under-torqued plugs can loosen up...I say undertorqued because just about every one I've seen blow usually happens after a tune up, be it 100 miles or 10,000 miles. My '97 launched #3 about 25K after I put plugs in it, FWIW. Now, the plug goes in at an angle, there aren't that many threads holding them in, so compression pressure from the cylinder in question causes the loose plug to kinda walk back and forth, wallowing out the threads until POOF.

I think in the '03 MY, the heads were slightly revised with more/better threads, but I'm not too sure.