# Spark plugs seizing on high mileage engines:myth or fact?



## noquacks (Jun 5, 2010)

Just what I learned- no reason plugs have to "fuse"/sieze just cuz high mileage. If maintained well (who knows if your previous car owner did) shouldnt be a problem.


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## D-rock (May 23, 2011)

I've seen more spark plug boots/wires coming apart more often then plugs seizing in the heads. If replacing spark plugs I would suggest also doing wires on 100,000 mile service interval engines unless coil over style.


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## toolaholic (Jul 31, 2011)

D-rock said:


> I've seen more spark plug boots/wires coming apart more often then plugs seizing in the heads. If replacing spark plugs I would suggest also doing wires on 100,000 mile service interval engines unless coil over style.


Yeah I put ac delco professional wires on w/ dielectric grease in the boots.


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## cjm94 (Sep 25, 2011)

The ford 3 valve engines have issues with the plugs breaking off. But most others your more likely too have a plug come loose and blow out than seize in.


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## ukrkoz (Dec 31, 2010)

1. you did put dab of Antiseize on the threads, right?
2. Your plugs are located in the side wall, going into combustion chambers at slight angle? Correct me if I'm wrong, there should be no head gasket where they at. Where's oil coming from then? Dripping from valve covers down?


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## toolaholic (Jul 31, 2011)

ukrkoz said:


> 1. you did put dab of Antiseize on the threads, right?
> 2. Your plugs are located in the side wall, going into combustion chambers at slight angle? Correct me if I'm wrong, there should be no head gasket where they at. Where's oil coming from then? Dripping from valve covers down?


Anti seize yes. Maybe plugs replaced before and coated w/ oil to install. I hear this is done. Torqued to 130 inch lbs. spec is 132. Probably a little tighter than factory spec due to anti seize Lubing threads.


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## toolaholic (Jul 31, 2011)

ukrkoz said:


> 1. you did put dab of Antiseize on the threads, right?
> 2. Your plugs are located in the side wall, going into combustion chambers at slight angle? Correct me if I'm wrong, there should be no head gasket where they at. Where's oil coming from then? Dripping from valve covers down?


Oh and it has the dreaded o ring distributor plug leak. But most oil leak goes toward the back of engine. You are correct as to plug location.


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## digitalplumber (Jul 8, 2011)

Happens on certain year model f150's.


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## rusty baker (Feb 13, 2009)

More common on aluminum heads than the old heads.


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## Fix'n it (Mar 12, 2012)

cjm94 said:


> The ford 3 valve engines have issues with the plugs breaking off. But most others your more likely too have a plug come loose and blow out than seize in.


yep. those should be removed and cleaned or replaced every 20k or less.
way to go ford.


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## imautoparts (Oct 10, 2012)

Fix'n it said:


> yep. those should be removed and cleaned or replaced every 20k or less.
> way to go ford.


Which is not very likely, since the spark plug change interval on a 5.4L Ford V8 (the ones most affected by this issue), is 100,000 miles.


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## ukrkoz (Dec 31, 2010)

which he has GM engine, not Ford. 

1. so, you have oil getting into chambers from somewhere, and drizzling onto threads. The way they are situated, oil either drips from the top and seeps onto the threads, likely, from valve cover gasket. So scope for those leaks. Or, you have oil getting inside the chambers, and not burnt completely during combustion, and sprayed over threads. Most of a plug is inside sticking out, you have what - maybe 3 full threads in the engine head? 
2. yep, heard that too. so this what happens. if you do NOT have continuous lubrication with oil, and put some oil onto plug threads to "lubricate" them, as it gets VERY hot, oil cakes and THAT will definitely bind plug to threads. Done it. That's why they came up with anti seize. Which is, basically, metalized powder in liquid form. Should also be used on lug nuts.
3. what you better off doing now is figuring out where that oil is coming from. As it will keep killing plugs. Or you will have to clean them every so many miles, and by that, you'll screw up plug seats sooner than necessary. Unless they have steel jackets, but somehow I doubt they do, as my 5.3L Vortech doesn't.


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## Fix'n it (Mar 12, 2012)

imautoparts said:


> Which is not very likely, since the spark plug change interval on a 5.4L Ford V8 (the ones most affected by this issue), is 100,000 miles.


indeed, beause the owners don't know about this issue. UNTIL they get a $800 tune up bill. :laughing:


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## toolaholic (Jul 31, 2011)

ukrkoz said:


> which he has GM engine, not Ford.
> 
> 1. so, you have oil getting into chambers from somewhere, and drizzling onto threads. The way they are situated, oil either drips from the top and seeps onto the threads, likely, from valve cover gasket. So scope for those leaks. Or, you have oil getting inside the chambers, and not burnt completely during combustion, and sprayed over threads. Most of a plug is inside sticking out, you have what - maybe 3 full threads in the engine head?
> 2. yep, heard that too. so this what happens. if you do NOT have continuous lubrication with oil, and put some oil onto plug threads to "lubricate" them, as it gets VERY hot, oil cakes and THAT will definitely bind plug to threads. Done it. That's why they came up with anti seize. Which is, basically, metalized powder in liquid form. Should also be used on lug nuts.
> 3. what you better off doing now is figuring out where that oil is coming from. As it will keep killing plugs. Or you will have to clean them every so many miles, and by that, you'll screw up plug seats sooner than necessary. Unless they have steel jackets, but somehow I doubt they do, as my 5.3L Vortech doesn't.


Thanks for your informative reply. You are a very knowledgable guy. I researched putting the plugs in and it went fine. Guess I'll look into the oil issues.


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## ukrkoz (Dec 31, 2010)

yeah, got to fix that, as crud accumulates on electrodes and slowly kills spark. take some brake cleaner, and spray onto the plugs side engine head, to clean it well. then it will show itself, should there be any leaks. otherwise, you were right the first time - it's engine head problem. or, valve stem seals leak oil inside, but it's easy to spot on hot engine, on fwy. simply drive behind your daughter and ask her to step on it. if you saw grey cloud coming out tail pipe, you got it. Those are good engines, they should run into 150-160 000 miles without any issues. 
Also, check coolant for oil droplets on dipstick and around radiator cap/neck.


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## toolaholic (Jul 31, 2011)

ukrkoz said:


> yeah, got to fix that, as crud accumulates on electrodes and slowly kills spark. take some brake cleaner, and spray onto the plugs side engine head, to clean it well. then it will show itself, should there be any leaks. otherwise, you were right the first time - it's engine head problem. or, valve stem seals leak oil inside, but it's easy to spot on hot engine, on fwy. simply drive behind your daughter and ask her to step on it. if you saw grey cloud coming out tail pipe, you got it. Those are good engines, they should run into 150-160 000 miles without any issues.
> Also, check coolant for oil droplets on dipstick and around radiator cap/neck.


Here's the thing. The car was bought from the inlaws for $1750. I changed tran fluid/ filter/ gasket for $70 in parts. Tune up was $100 including plugs, wires and the thexton engine mover. New headlights for $60. One taillight for $50. New hoses are slated for summer 2013. I bought car cause first 60,000 miles were in it's first 2 yrs of life ( company sales car)and the last 10 yrs the mother in law put 35,000 miles on it. My daughter only drives it 25 miles a week. A lot of work I did(plugs/tranny) was to access condition of tran and engine as father in law would only tell me car was serviced every year. I bought cause tranny fluid looked good and engine ran fine. So I really don't want to invest too much more in a car that I want my oldest to drive for 2 yrs and my youngest to drive another 2 yrs. I want to keep it for a total of 4 years and the way the miles are being put on 6,000 miles. At least with new plugs wires and tran fluid car shouldn't let my daughter sit. BUT I will look into oil problem if it can reasonably be fixed. Tempted to epoxy dummy plug rather than pull throttle body to fix leak.


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## toolaholic (Jul 31, 2011)

Plus a ac delco fuel filter for $12 and a 20mm long style wrench( one it's only uses gm fuel filters) for $14.


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## Chokingdogs (Oct 27, 2012)

This has the potential to be fact.....

Obviously dissimilar metals - e.g. aluminum against steel/iron - can corrode together.

Spark plugs into aluminum heads is that exact scenario. Your mechanic was probably being cautious, assuming you may have no knowledge of when ( if ) the plugs were replaced in a car nearing 100K miles.

Who knows why, exactly, they all came out easily. Could have been recently replaced, the oil leak, anti-seize on threads, etc. When replacing, you can use anti-seize to help aid removal next time around, but use it sparingly, a little goes a long way. Bear in mind there's some who frown on that practice, as they seem to think/believe anti-seize inhibits a proper ground path, and spark efficiency can suffer. 

Oil on threads can come from a couple areas, chances are the rocker covers. I'm not familiar with that engine, so I don't know if plugs go in from the top - like a GM 4 cylinder, or in from the side like on your age old Chevy small block. If they go in from the top, a "quasi-hemi" setup, there'd be gaskets under the cover in addition to one around the perimeter.

A bad valve stem/seal can also lead to oil on the plug threads, from the inside out. If the car puffs blue smoke upon startup after sitting for a while, that's most likely a bad valve guide/seal.

The Ford deal and broken plugs wasn't so much metal fusing together, rather the spec'd out plugs for those engines extended beyond the threads in the cylinder head. So what ended up happening was several plug threads being exposed in the combustion chamber, and over time they'd corrode and get all funked up that when trying to remove all that gunk acted as a wedge and the plug would break and/or threads in the head would strip.


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