Blown out spark plug- Did I dodge a bullet?

[Vipergrün]

My son noticed what had sounded like a small exhaust leak on his 06 Mustang V6. Last night that turned into a very loud noise. I crawled under the car this morning and see a spark plug hanging by the plug wire. There was very slight gnarl on the threads on the end of the plug. Went and bought new plugs, threaded right in and tightened it up. All of the other 5 plugs were loose, replaced them all. Car has never run better. I was fearing head work to re-thread the hole.

Is it normal for plugs to back out, blow out, and not screw up the threads? Weird, feel like we dodged a major bullet.

Whew...for now, until the next thing happens :--)

-B

[DanielDudley]

I have seen it happen. I have also seen a plug well get filled with oil, with oil seeping past the loose plug, causing the car to smoke severely at startup after not running for a few days.

[John Rogers]

If the head threads strip out it is an easy fix if you are mechanically inclined. If not a good mechanic can do the insert in an hour or two. If your case did you torque the plugs since most new cars have some sort of thing like tighten hand tight then 1/2 turn or such.

[911boost]

I blew one out in my 78 Westy, threads and all.

As mentioned I did a Time-Sert.

[Ayles]

Blew one put of my bug many years ago. My dad put in a time sert.

[Superman]

Lots of people over-torque spark plugs, which damages the (usually) aluminum threads in the head. Tears them. Then the plug blows out.

If the spark plug as a crush washer on it, then proper torque is generally achieved when you can feel that the crush washer has finished crushing. No more. 20 lb/ft.

[carreradpt]

I had a plug blow in mine (pcar). Threads were done. Time cert and a top end. Good as new.

[pen15]

Super common to blow out plugs in ford 5.4 engines threads and all. Lots of nice kits to repair them nowadays.

[Vipergrün]

Thanks for the replies. Really odd that I could screw the new plug all the way in. Didn't feel any binding as it went in. Seems like a fairly common issue in some of these era mustangs.

[sc_rufctr]

"All of the other 5 plugs were loose,"... Did some hack mechanic forget to torque up the spark plugs?

[pwd72s]

Originally Posted by Superman

Lots of people over-torque spark plugs, which damages the (usually) aluminum threads in the head. Tears them. Then the plug blows out.

If the spark plug as a crush washer on it, then proper torque is generally achieved when you can feel that the crush washer has finished crushing. No more. 20 lb/ft.

Since it's often difficult to impossible to get a torque wrench on a plug wrench, a good P-car mechanic gave me a tip for aluminum heads. With a new plug, tighten finger tight, then 1/2 turn to crush the washer. If installing an original plug, 1/4 turn. That puts you in the proper torque range. I don't see why this wouldn't work with iron engines as well.

(edit) A s197 Mustang forum you or your son might wish to sign up for. Very tech & hop up oriented group. There is a special section for the 2005 and up 4.0 V-6 Mustang.

http://s197forum.com/forum/index.php?

[asphaltgambler]

Originally Posted by sc_rufctr

"All of the other 5 plugs were loose,"... Did some hack mechanic forget to torque up the spark plugs?

^^^yes - they did^^^

[john70t]

It could be just simple engineering:
Engine cases are made out of huge blocks of soft magnesium/aluminum/other.

Those materials are lightweight and made to do their job.
But they are vulnerable to their specific applications properties and usage.
(Obviously a superlightweight highway runner which is designed to last is not to be used as a drag strip torque monster.)

The parts that seal, grip, and/or slap together repeatedly usually need a much higher strength rating than the the whole engine block case has.

[Laneco]

One basically falls out and the other 5 (so six total) are loose? These weren't put in right. Finger threaded and that's it. Nothing peculiar other than crappy workmanship.

angela

[widebody911]

Use some Red Locktite to keep it from happening again

[Vipergrün]

Originally Posted by widebody911

Use some Red Locktite to keep it from happening again

JB weld works better. LOL

I have a feeling the PO did the plugs before.....and did a piss-poor job.

[onewhippedpuppy]

Originally Posted by pwd72s

Since it's often difficult to impossible to get a torque wrench on a plug wrench, a good P-car mechanic gave me a tip for aluminum heads. With a new plug, tighten finger tight, then 1/2 turn to crush the washer. If installing an original plug, 1/4 turn. That puts you in the proper torque range. I don't see why this wouldn't work with iron engines as well.

(edit) A s197 Mustang forum you or your son might wish to sign up for. Very tech & hop up oriented group. There is a special section for the 2005 and up 4.0 V-6 Mustang.

S197 Mustang Forum - S197Forum.com

That's how I do it too. Some of the plug companies will actually put a diagram on the box, finger tight plus some amount of twist with a ratchet. Torque wrench is nice, but on most modern cars you are damn lucky to even get the stupid things in/out.