Loose Spark Plug

[TallPaul]

Yesterday I heard a light knocking only to discover a spark plug that was loose and vibrating in its hole. This is the plug I pulled 5000 miles ago to check and when I reinstalled it I think I used Permatex Anti Seize on the threads, which is what it is meant for. Anyway, I tightened the plug (adding Anti Seize not at the time remembering having done it before or not). Today, after I drove 35 miles I found it loose again. I tightened it more than the last time. I think maybe I just did not tighten it enough before.

I don't think the Anti Seize should make it loosen and like the stuff because it also lubricates so the plugs thread in nicely, instead of before it would be hard to thread in with regular oil on the threads.

The plugs are in a '95 F150 4.9L and are taper, no metal crush washer or anything like that.

Thanks.

 

[Quest]

For non washer type spark plugs, you should consider torquing it to about 16~18ft/lbs and no more (dry).

I don't like to use antiseize on spark plugs (with or w/o washers). I would insist on torquing them to factory specs and remove them annually for visual inspection (platinum plugs included). This helps in keeping the deposit buildup on the plug threads to a minimum so that next time you pull it off, it would have a lesser chance of seizing/cross-threading in the block.

We had several instances of O2 sensor/cat converter toxification due to lead in antiseize used on spark plug threads.

 

[Gary Allan]

I have one on my 3.0 that works out every 1500 miles or so. I'll just look down and find a wiggling wire. It's only happened twice after the plug blew out of the hole while I was on the highway. I kept wondering what the static was on the radio..finally I turned the radio off and put the van in neutral and revved it

Put a new plug in ..and about 4 months later ..loose plug. Tightened it down ..no problem...found it loose again a few weeks ago. I got out some industrial pipe dope called Rectorseal. I just applied a little to the top threads of the plug. It should be enough to hold it fast without making it impossible to remove.

 

[road_rascal]

I use anti-sieze on all my spark plugs (cars, vans, motorcycles and yard equipment). I have never had one come loose. When I pulled the plugs from my '01 Windstar at 54,000 miles and changed them I didn't have any carbon buildup. Sounds like you may need to retap the hole and helicoil it.

 

[TallPaul]

I have no plans on retapping the hole or anything like that. The threads appear to be fine. I think it is mostly a matter of my being too cautious against overtightening. That combined with the lubricity of the Anti-Seize and she goes loose. At least the plug boot is very tight and holds it from full back out like Gary Allen had.

I drove 16 miles this morning and it is still tight. I will continue to check it. If it loosens again I will try to get my torque wrench wormed into place. As it is I am using a standard ratchet handle (prob. around 7 inch), so that alone should prevent overtorquing it. Anyway, we'll see.

BTW, I guess having the Anti-Seize/lube messes with proper torquing.

 

[kenw]

quote:

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Originally posted by TallPaul:
BTW, I guess having the Anti-Seize/lube messes with proper torquing.

---

it shouldn't. but have you checked for a crush washer that may be missing?

 

[Schmoe]

Geesh...what the #ell is wrong with Fords and loose or blowing spark plugs this past decade???

 

[Mud]

Seems to be an issue with 4.6, 4.9 fords and more than a few gm lt/ls engines.

It's not the anti-seize as a general rule. If that particular hole was tapped a bit differently at the factory or the plugs are not tight, they will loosen.

Just my experience - I have used a light touch of anti seize on plugs and bolts for close to 30 years and have simply not had issues with things loosening, poor conductivity, any of that stuff. However, if I had a situation like that I would certainly try a dry application or maybe a little thread locking compound (not the permanent type though!)

 

[TallPaul]

quote:

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Originally posted by kenw:
... but have you checked for a crush washer that may be missing?

---

I am 99.999% sure these do not have crush washers. Would anybody with a 4.9L Ford I-6 be able to verify that?

 

[Ugly3]

quote:

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Originally posted by TallPaul:
I have no plans on retapping the hole or anything like that. The threads appear to be fine. I think it is mostly a matter of my being too cautious against overtightening. That combined with the lubricity of the Anti-Seize and she goes loose. At least the plug boot is very tight and holds it from full back out like Gary Allen had.

I drove 16 miles this morning and it is still tight. I will continue to check it. If it loosens again I will try to get my torque wrench wormed into place. As it is I am using a standard ratchet handle (prob. around 7 inch), so that alone should prevent overtorquing it. Anyway, we'll see.

BTW, I guess having the Anti-Seize/lube messes with proper torquing.

---

The last I saw was that the torque should be reduced to 80% when anti-sieze compound is used.

 

[TallPaul]

Ok, my torque wrench got up to 20 ft/lbs without budging it, so it is at least that much. Anyway, good I have the anti-seize for removal and after about 55 miles today it is still nice and tight.

Thanks all.

 

[Drew99GT]

quote:

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Originally posted by TallPaul:

quote:

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Originally posted by kenw:
... but have you checked for a crush washer that may be missing?

---

I am 99.999% sure these do not have crush washers. Would anybody with a 4.9L Ford I-6 be able to verify that?

---

I checked NGKs website; they do not. They are a tapered seat for your application. They are an 18mm tapered seat (not gasket), so they need about 1/16th of a turn past finger tight, or 15-20 ft. lbs. for an iron head, according to NGK.

 

[TallPaul]

quote:

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Originally posted by Drew99GT:
They are an 18mm tapered seat (not gasket), so they need about 1/16th of a turn past finger tight, or 15-20 ft. lbs. for an iron head, according to NGK.

---

My Haynes manual says 20 ft/lb, but my shop manual (albeit 1984) says 10-15 ft/lb. I think 10 would be a safe bet with the anti-seize in place. May put the torque wrench on it tonight just to see where I'm at.

Hey, I have an inch pound torque wrench too. Wouldn't 10 ft/lb = 120 inch/lb? Much easier to read a wider scale than the little 1/4 inch off center of the foot/lb scale.

 

[JAYCEE]

I have this same truck. I use Autolite 5125 from walmart. They do not have washers.

FWIW I had this same prob in a mazda pickup. The #1 plug loosened up several times on me. There was oil sprayed around the plug and after this burned off it stopped loosening up.

The urge was there for me to overtighten. Just check it often and it should clear up.

 

[moribundman]

The 12v Audi motor tends to shake spark plugs* loose over a few thousand miles. I can't imagine what would happen if I were to use anti-seize. Luckily, a loose spark plug makes quite a racket. You think you're driving a tractor. After changing my spark plugs, I retorque them after about 500 miles and check them every oil change. For new plugs I use a torque wrench (30 Nm). When I put used ones back in I screw them in hand-tight and give them another +15 degree turn.

*NGK BKUR6ET-10 with crush washer

 

[Whimsey]

Wow, that's strange with that engine, it has a cast iron head. I had a 1980 F-100 with the 4.9 and a 1989 F-150 with the same engine. Once tightened the plugs never budged. Though until the last set of plugs installed in the '89 I didn't use antisieze. And believe me I regret not doing so. It made removal difficult sometimes. I did use antisieze for the last set of plugs I installed and 60,000 miles later, no problem. Still nice and tight. For the previous plugs without antisieze I always changed them out around 30,000 to 36,000 miles.

Whimsey

 

[Vstrom]

I too use antiseize on plugs and always have....never ever had one come loose on anything

 

[jsharp]

quote:

---

Originally posted by Drew99GT:

quote:

---

Originally posted by TallPaul:

quote:

---

Originally posted by kenw:
... but have you checked for a crush washer that may be missing?

---

I am 99.999% sure these do not have crush washers. Would anybody with a 4.9L Ford I-6 be able to verify that?

---

I checked NGKs website; they do not. They are a tapered seat for your application. They are an 18mm tapered seat (not gasket), so they need about 1/16th of a turn past finger tight, or 15-20 ft. lbs. for an iron head, according to NGK.

---

I cannot understand why Ford keeps using these tapered seat plugs. I've owned Fords for years and cuss them eveytime I have to remove them. If you torque them enough to keep them tight they lock in the taper so tightly you need a breaker bar to remove them.

Another dumb idea they should have abandon decades ago...

 

[TallPaul]

quote:

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Originally posted by jsharp:
I cannot understand why Ford keeps using these tapered seat plugs. I've owned Fords for years and cuss them eveytime I have to remove them. If you torque them enough to keep them tight they lock in the taper so tightly you need a breaker bar to remove them.

Another dumb idea they should have abandon decades ago...

---

I have had three of these engines in the past 27 years. It seems they always are a bear to loosen, but then I was a ham fist for years. I remember once breaking off the plug trying to get it out. Fortunately the hex part was still in the block and in good shape. Took it down to the corner service station and had them remove the plug with their air impact wrench. It worked. Thankfully it was a straight six and they could get at the plug easily.

 

[loudist]

Antiseize will cause one to over tourque the plugs, lugnuts, whatever, because of the sliperiness of it.
Overtorqueing the plugs is one of the reasons for plug blowout on fords as it distorts the 4 threads in the aluminium head causing thread failure.
There is a formula, that escapes me right now, for adjusting the torque when using antiseize.
Most sparkplug torque specs are 15 to 18 pounds (no antiseize), and no more.