quick question, loctite on spark plugs

Discussion in 'SN95 4.6L Mustang Tech' started by OleYellarGT, May 25, 2005.

  1. NO do not use locktite. i am retracting this now after what i saw today on a test i did. and i showed it too my boss.

    to start off i take responsiblitiy of this but we were told to do this on new lightings ( by ford back in 2002-3) and was recomended to use this method for all mod motors.

    it turns out that while the locktite does stop the plug from loosening and backing out. it can cause some thread damage. i must of got lucky on my car.

    i took a 5.4 with a spun bearing we had in the shop. this motor had plugs put in by us at 100k miles with locktite and the motor was pulled at about 139,000 i removed the plugs from it as a test 7 of the plug holes the threads were fine. one of them showed some thread damaged. and upon closer inspection i think this could have been caused by the locktite.

    i showed this my boss who was working today. and we are going too look into it.

    i think when this was told too us by ford they knew that the locktite will stop the plug from backing out. but they probally never considered removal. they were proballly only concerned with stoping the plugs from backing out and with a 100k plug they figure it will be well out of warrenty.

    i gave ford a little more credit than they deserve and took this as meaning that it's safe. i must have gotten lucky on the ones i did remove

    well i have used locktite now on a few mustang and lightings i work on personally and if a problem comes up i am going too get them free heads.

    i checked mine again and showed no thread damage. so i put in another set of plugs after i cleaned the threads.

    so now the only thing i can think of is the tried and true tourqe it down too spec and recheck them once in awile.

    well i am not perfect and i doubt many of us are.
  2. Thanks for the info Mike. It's very much appreciated. Pearl02.

  3. Way to go!

    I never had any doubt that the Ford rep didn't think about the long term effect of loc-tite, nor the removal of the plug installed with loc-tite. They were only thinking of the short time solution.

    I was told YEARS ago to put anti-seize on the plugs because they are made of iron/steel and the head is aluminum. The two metals heat/cool at different rates, and there is a chemical process that can occur and seize the plug to the head. In 1999 I found this out the hard way by having NOT used anti-seize. When it came time to remove the plug, I broke it clean off in the head. The ceramic along with the nut snapped off, leaving the threads and the tang inside the head. No matter what I did, it would not come out. I had to take it to a shop where they removed the head and had it machined. To this day, I use a little dab of anti-seize on every aluminum head when installing plugs.

    I'm sorry to have crossed you, but it was your info that I had a problem with, not necessarily the messenger.

  4. Now see? That's what I'm talking about. Refute info without attacking character.

    You are exactly right about the use of anti-seize to prevent the plugs from fusing itself into the head. When I did electrical work we used a similar material on the copper wire to prevent aluminum rust on the aluminum buss. Two disimilar metels under heat could cause a failure by reducing the conductivity. By using anti seize it has the same effect by preventing the rust and seizing the plugs to the head.

    As a side note I have sent an email to the makers of loctite to see if they recommend or not using this particular product for this purpose although it looks like it has mostly been refuted now. I post up when they have replied.

  5. yeah that sucks when a plug seizes in. used too happen on the old 5.8's in the f-series and broncos a LOT. in fact it happend so often that when we saw one come in for a tune up we warned the customer about the chances of them breaking off.

    on the bright side the modular head does not seem too have problems with seizing the plugs in.but a dab of anti-seize will not hurt.
  6. crew_dawg16.

    yeah it been known for along time that the heads had a design flaw. for the most part this was the early heads. and was only a problem on the 5.4's but some of our 4.6's are shooting the plugs out now.

    i am not surprised the problem showed up first on the motors with the highest cylinder presures. like the S/C lighting and the 5.4 F-150 motor ( a motor with less overlap will have high cyl. presure) the new 2003+ heads have more threads to fix this problem. but where does that leave the rest of us ?

    no matter what the plugs on these motors will back out. even if tourqed right it can happen. and since the loctite idea can cause damage that can't be done.

    the only thing we can do is tourqe them too spec and check them once in awile.
  7. You THE MAN !!


  8. Thanks dad! :rolleyes:

  9. :D I've been called worse.
  11. No Sweat man........

    Thats why we are to share and learn.

    I am pushing 38 and learning more everyday..........I LOVE IT !!!

    Keep up the good work !
  12. E-mail I recieved from the makers of Loctite. I'm still beating this horse but thought I'd share...

    Subject: Loctite Request Number 50054
    To: [email protected]
    From: [email protected] Add to Address Book
    Date: Tue, 31 May 2005 10:38:56 -0400


    Thank you for your inquiry. Generally, you don't put a threadlocker on
    spark plug itself. Rather, a helicoil is usually bonded into the
    threads using a high-temperature product like 620. However, if you want
    use something specifically on the spark plug threads, most of our
    are good to about 300F, with some, like the 620, good to 450F. These
    permanent products that will likely need heat and force to remove.

    Please feel free to contact our Technical Information department
    at (800) 562-8483 if you would like to discuss in more detail.


  13. mis-post, sory.