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Thread: Spark plug O-rings

  1. #1
    Freeman LibertyAddict's Avatar
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    Default Spark plug O-rings

    Looked everywhere and can't find info on this.

    The o-rings for the spark plugs.
    Where are they?
    How to change them?
    Where to buy them?
    Are they even a thing in the 4.6L engine?

  2. #2
    GMN Regular DerekTheGreat's Avatar
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    That's because they don't exist. Almost like Blinker Fluid or Muffler bearings. Some spark plugs have washers on them though, is that what you're talking about? I'm not a 4.6 guy. I know fuel injectors have O-rings though.
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  3. #3

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    Not a thing. Are you changing the spark plugs? If you dont already know changing the plugs on a 4.6 2v can be risky due to only having a few threads on pre 04 heads.


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    Road Warrior Kodachrome Wolf's Avatar
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    Quote Originally Posted by 87GrandMarq View Post
    Not a thing. Are you changing the spark plugs? If you dont already know changing the plugs on a 4.6 2v can be risky due to only having a few threads on pre 04 heads.


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    Good rule of thumb is 14/ft-lbs and no anti-seize. Hulk torque spec may result in spark plug ejection after a while.

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  5. #5

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    Quote Originally Posted by Kodachrome Wolf View Post
    Good rule of thumb is 14/ft-lbs and no anti-seize. Hulk torque spec may result in spark plug ejection after a while.
    Also retorquing them after a few heat cycles to ensure theyre still in spec and havent backed out.


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  6. #6
    No mean-spiritedness here. IPreferDIY's Avatar
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    Default

    Also torquing/retorquing them only when the heads are stone cold. Torquing on feeble aluminum threads when they're warm is just asking for trouble. Since most shops would probably not wait, I wonder if that's where a lot of the problems come from.

    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
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  7. #7

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    I think its the lack of information (or research on the person whos changing them), inexperience with aluminum heads (especially during the 90s-00s since Ford people were used to iron cylinder heads) and Fords lack of judgement. It took them from 91 all the way to 04 to finally give the 2v heads enough threads to lower the chance of a blowout substantially.

    Also it would seem that its more common on the 5.4 and in trucks. It would seem that perhaps trying the service the plugs on the rear cylinders are probably the big offenders.


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  8. #8
    Beater gonna beat sly's Avatar
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    There's fuel injector o-rings. And fuel line o-rings. Then the AC system uses o-rings too, but spark plugs use angled seats or metal gasket washers.

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  9. #9
    Freeman LibertyAddict's Avatar
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    I asked because I see oil on one of the spark plugs.
    Changed them all a few months ago and I noticed one particular plug was darker and dirtier than the others. I just pulled that one out and cleaned it. The car still idles rough, it shakes, sounds like it loses power, like it wants to shut off.
    I'm about to order some new ignition boots and I figure the wiring needs replacement too BUT when I type "Grand Marquis ignition wiring" I get varied results. I could also change the ones that are bad for now and then do the whole thing when I have time. Now a question: How do you check which one is bad? Do you unplug them without disconnecting the battery and with a multimeter check for 12v?

    Thanks for all the quick replies. One would think a forum about a car that is out of production shouldn't have so much activity, but it does! Great!

  10. #10
    Beater gonna beat sly's Avatar
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    Could be oil leaking from the valve cover gaskets along the top edge next to the intake manifold and draining into the plug hole. Can't think of any other non-catastrophic failure mode.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
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    Quote Originally Posted by gadget73
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  11. #11
    Freeman LibertyAddict's Avatar
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    Quote Originally Posted by sly View Post
    Could be oil leaking from the valve cover gaskets along the top edge next to the intake manifold and draining into the plug hole. Can't think of any other non-catastrophic failure mode.
    It's clean around the plug, no signs of leakage from the VCG.

    I had a leak on the driver's side VCG, bottom of the cover, towards the back of the car, and replaced the gasket a couple of months ago. No more leaks from that. Now FTR, that odd dirty spark plug is on the passenger's side closest to the front of the car, the complete opposite of that old leak.

    When I installed the new spark plugs I noticed the shaking calmed down for some time but it started to come back gradually and a few days ago it popped the check engine light.
    My suspicion of bad contact on the wires is grounded on the possibility that when I changed the SPs I moved the wires in a way that they made the right contact, and later after a gazillion potholes(easy to achieve here) they shifted back into damnation.

  12. #12

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    Its most likely coolant from the intake manifold/coolant crossover. What year is your car? Im assuming its a 98+ because usually when this happens it shorts the coil over plugs (cops) and requires a new coil.

    You cant really test a cop, you can perform a resistance test on the secondary circuit but imo it doesnt tell you much. You could try a new coil boot but youll need a new coil eventually.

    For what its worth, I drove through a deep puddle that splashed all under the hood on my 98 p71. It didnt drench the top end and nothing was affected except coil number three crapped out on me. I replaced it with an ebay coil and didnt have another issue up until I sold it.


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    GMN Regular DerekTheGreat's Avatar
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    Yeah, what year is your car? Don't the early 4.6's have issues with valve stem seals? I believe seeing oil on the spark plug threads indicates oil is getting into the combustion chamber somehow, stem seals can be a way. It's definitely an issue with higher mileage LoPo 302's, the rear most spark plugs anyway.
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  14. #14

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    Hmm I forgot about that, yes thats true. Though I think that was an aero era issue. It could still be the case though.


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    Beater gonna beat sly's Avatar
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    Yeah... knowing the year of your car would help. And yes the valve stem issue was an aero thing that was supposed to have been fixed in 95 or 96. But even the better seals do eventually wear out. It just takes longer.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
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    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
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    Overhead, some poor bastards are flying in airplanes.

  16. #16
    Freeman LibertyAddict's Avatar
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    Quote Originally Posted by 87GrandMarq View Post
    You could try a new coil boot but youll need a new coil eventually.
    What's the difference?

  17. #17
    Freeman LibertyAddict's Avatar
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    It's a 98. 101k miles.

    It's not that the plug is drenched in oil, just slightly on the threads, and dark(carbonization?) on the spark tab.

    I ordered the coils on AMZ, all 8 of them, last night and they're on their way already. Under 30 bucks the set.
    Asked once at Advance Auto Parts and the guy told me something like 38 bucks per piece!

  18. #18
    Freeman LibertyAddict's Avatar
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    BTW, coolant levels are fine.

  19. #19
    Freeman LibertyAddict's Avatar
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    Valve stem seals... Got some homework to do.

  20. #20
    No mean-spiritedness here. IPreferDIY's Avatar
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    Quote Originally Posted by LibertyAddict View Post
    What's the difference?
    I wasn't sure initially if you were talking about spark plug wires (on an aero) or COPs, but since it's COPs, the boots are the rubber part, and sometimes you can get away with replacing only the boots. Getting a new set of COPs for so cheap is so much more convenient though, and you can keep the old but good ones as spares.

    Also, not sure what year the problematic all plastic intake manifold started, but the failure of the coolant crossover on my 2000 MGM was nothing more than a teardrop leak on the front passenger side that I happened to notice when it was warmed up. Enough coolant had accumulated in a spark plug well to cause problems.
    Last edited by IPreferDIY; 05-21-2019 at 12:44 PM.

    2000 Grand Marquis LS HPP, a hand-me-down in 2008 with 128,000 km; 175,000 km as of July 2014
    mods: air filter box "tuba" (in place of the "trumpet"), headlight relay harness, J-mod (around 186,350 km), 70mm throttle body, NKL4 PCM (from a 2000 CVPI, nothing great there apart from highway cruising), KYB Gas-A-Just shocks (after >202,000 km on originals)

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