Blown spark plug.

[Lubener]

Originally Posted By: edwardh1
what are 1/2 threads and what are 3 threads?
My toyota plugs have about 1 inch of threads, what did ford change?


Three threads holding the plug in place. One of Ford's better achievements. Plugs breaking and dropping in the cylinders too. That's why many shops charge big dollars to change the plugs on certain Ford's (V8's). The plastic intake manifold with the alternator stressing it was another inferior item which would break, sending coolant everywhere.

 

[HangFire]

A steel bolt, threaded into a steel or iron medium, assuming no high temperature high pressure gas on one side, approaches full strength at 3 full turns.

Some engineer(s) at Ford assumed that it was OK to extrapolate this rule of thumb to Aluminum heads over a combustion chamber, and designed the infamous 3-thread Triton head.

This is NOT a matter of mechanics cross-threading or over-torquing. This is a design that WILL fail over time. It happened to a friend of mine while driving home on his factory installed plugs.

This is a different problem from the Ford spark plug design that followed almost immediately after. The spark plug had a long narrow electrode that broke in two on removal, and part of it stays in the head when the top is removed.

 

[Wheel]

Thread strength is related to the diameter of the threaded fastener. A safe margin of strength in steel is achieved in 1x the diameter of the nominal diameter of the thread. Cast iron should be 1.5 the diameter, and aluminum 2x.

In steel, 3 threads gives about 84% of max strength. In aluminum and cast iron, it is less.

The do make a threaded insert for just such a disaster. I'd fix it, and drive it.

 

[Colt45ws]

It was $129.16 OTD for Ford to fix it.
$105 for 1hr Labor
$4.20 for SP413 plug
Then Shop supplies and tax took up the rest.
I had supplied a new Denso coil for them to install.
Heres a good visual reference.
Half-thread spark plugs (These are obsolete and all heads can take the full-thread plugs but it shows how much thread is in the head.)

Full-thread plugs

Anyways, I can tell it runs smoother at an idle in-gear. I thought I had another coil on the way out (which is why I had a spare coil standing by) but obviously it had to do with the plug getting pushed out.
Matter of fact I was at a drive-thru Weds afternoon and noticed a tapping noise coming from my engine I hadn't heard before. I investigated in the parking lot and though I did figure out it was coming from the #2; I thought that it was a loud injector or something.
But now I know what to look for when the next one starts getting pushed out.
Oh, and I noticed after I got home they put this work in under my 2004 VIN in their system. Oops.

 

[Colt45ws]

Oh, on a oil note.
Think I should change the oil?
I have 9000 miles on this fill of Maxlife. Its been getting a quart of oil at least every 3000 and the filter was changed at 5500.
Right now its about a quart low again.
Im thinking Im going to put another quart in and run to 11k or so. Just to let the oil already in there soak up some of the contamination before I change it.
I wont feel as bad putting in another quart to go 2k, than draining and filling every 2k.

 

[InfmousCornholio]

Originally Posted By: zrxkawboy
Originally Posted By: Colt45ws
I then drove it 130 miles back home with no spark plug in the number 2 hole. .

\

I've done "similar."

 

[Nick1994]

9,000 on MaxLife? Change it!

 

[Colt45ws]

Originally Posted By: Nick1994
9,000 on MaxLife? Change it!

It sounds like a lot but Ive put a fair amount of fresh oil into it, plus the filter change.
1qt@2800
1.5qt+filter@5500
10oz of Liquimoly ceratec@6500
And now another quart @9000
Ill take it to 11k.

 

[edwardh1]

Originally Posted By: Lubener
Originally Posted By: edwardh1
what are 1/2 threads and what are 3 threads?
My toyota plugs have about 1 inch of threads, what did ford change?


Three threads holding the plug in place. One of Ford's better achievements. Plugs breaking and dropping in the cylinders too. That's why many shops charge big dollars to change the plugs on certain Ford's (V8's). The plastic intake manifold with the alternator stressing it was another inferior item which would break, sending coolant everywhere.


you always wonder why an engineering supervisor approved changing from "how we did it last year without problems" . was there a perceived cost savings? that was big?