# Loose spark plugs



## XtremeRevolution (Jan 19, 2012)

c6vette said:


> I have a 2011 Cruze Eco (1.4 Turbo) about every 3000 miles or so I find 1 or 2 loose spark plugs which result in a ticking sound in the engine .
> I torque the plugs to about 200 in lbs and the sound goes away, but 1 or 2 continue to loosen over time. Anybody have the same experience.


Torque spec is 18lb-ft. I usually give them 22lb-ft if I'm re-tightening a plug that has a crush washer that's already been crushed. 

Try replacing your plugs?


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## NickD (Dec 10, 2011)

Actually yes, when some idiot either cross threaded a spark plug or over torqued the plug with a 460 ft-lb impact wrench. Wasn't much of a problem with cast iron heads, aluminum is much softer. So do your head threads look like?

KD makes a tool with steel inserts, taps, and a special glue if this is the problem, good to remove the head if you can, but can get by, by putting the piston at TDC on the compression stroke, and using a hose connected to a power vacuum to get most of those chips out.










Or the threads on your spark plugs, generally can screw those in about 90% and check the top of the plug for side play, should be very little. Another bit of a trick is just to put a drop of Loctite on the spark plug threads, ha, an trade it off. 

200 in-lbs is 17 ft-lbs, darn close to specification. 

Did you get this car new or used, ha, nobody touches my plugs except me, and do put a thin coat of anti-seize on the threads. Steel in aluminum with current is electrolysis, they can be welded in. Anti-seize helps to prevent this. Also coat the insides of the boots with dielectric grease so they don't bake on.

Regarding my Cruze, no, they never came loose.


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## obermd (Mar 3, 2012)

I've discovered that I have to torque to about 220-225 in-lbs to keep my plugs from coming loose and chirping. 200 in-lbs is asking for chirping plugs.


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## Robby (Mar 1, 2013)

And that spec is for dry/clean threads.

Some folks put never seize on plug threads.....even though the plug (and engine) manufacturers say not to.

A lubed plug thread will not hold torque.

Rob


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## c6vette (Jul 24, 2011)

Yes, replacing the plugs is probably the way to go. Cheap investment. I probably started the problem a few years back when I removed the plugs to change the gap. As stated in some of the responses here,plugs with gaskets should be replaced once the gasket is crushed.


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## NickD (Dec 10, 2011)

Robby said:


> And that spec is for dry/clean threads.
> 
> Some folks put never seize on plug threads.....even though the plug (and engine) manufacturers say not to.
> 
> ...


Yeah that's what they say, but been dealing with aluminum heads for over 35 years and learned the hard way. Been using anti-seize ever since, never pulled out a plug with the aluminum heads plated to it, and never had a spark plug come loose.

If they would mold in steel inserts wouldn't be a problem, but don't consider it their problem, consider it yours.


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## Robby (Mar 1, 2013)

NickD said:


> Yeah that's what they say, but been dealing with aluminum heads for over 35 years and learned the hard way. Been using anti-seize ever since, never pulled out a plug with the aluminum heads plated to it, and never had a spark plug come loose.
> 
> If they would mold in steel inserts wouldn't be a problem, but don't consider it their problem, consider it yours.


Your car.......your call......

Rob


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## NickD (Dec 10, 2011)

Robby said:


> Your car.......your call......
> 
> Rob



Ha, not the only very knowledgeable person that does this, maybe time to contact my old engineer friends. Well at least the ones that haven't kicked the bucket yet.


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## ChevyGuy (Dec 13, 2014)

Robby said:


> Some folks put never seize on plug threads.....even though the plug (and engine) manufacturers say not to.


Any idea if the threads are pre-treated to not need anti-seize? Or perhaps the spark plugs are also aluminum? Otherwise, I'm not sure why they'd give that advice.


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## Robby (Mar 1, 2013)

If you go to the various plug manufacturer sites they recommend against it.

They say there is a coating.

Regardless, by applying any type of lubricant to a plug thread, regardless of what it is being screwed into, invites one of two type failures.

1. A lubricated thread will cause highly inaccurate torque readings.

2. A lubricated thread invites overtightening, resulting in the threads pulling out of a aluminum cylinder head, often resulting in a plug blowout.

Naturally, if you are the second party taking things apart for repair, a assumption is made that the plug blew out because it was cross threaded.

If you are removing a plug that has been overtightened, causing the threads to collapse in the head and come out with the plug, you tend to assume the plug seized in the head and that is why the threads ripped out.

Except, there is one fact that has to be taken in consideration.

The only time I have run across aluminum head plug thread damage was after someone had replaced plugs.

I have never had a factory installed plug (with exception to Ford 4.6 and 5.4 V8's) frozen in a head or come out of the head pulling the threads out with it.

So over 52 years of dealing with aluminum engines, all the way back to GM's first aluminum V-8 from 1961 (yep....wrenching since age 13) I still haven't found a factory installed (dry) plug coming loose or blown out.......

Have any Cruze models had their factory installed, never removed, dry install plugs come loose?.....Before responding, I said, factory installed, never removed for inspection, plugs

Rob


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## NickD (Dec 10, 2011)

Not the only problem, with some engines the, about 3/16" inch, the threads are exposed to carbon built up in the combustion chamber with rock hard carbon, those threads aren't doing a thing to hold that plug on.

And what is holding the spark plug in? The friction between the base of the plug with the gasket to the surface of the head, that doesn't get any anti-seize on it, just like a painted surface on the thread themselves, and you cannot deny that dissimilar metals like this with a constant current flow to ground causes electrolysis. 

Course, another problem is leaving them in there for 75K miles or so.

Another problem is the boots themselves, they bake on to the plugs. With spark plug wires, had to make my own tool, piece 5/8" flat steel with a U cut into the end of it bend to a 90* angle. Pulling on the boot is like a Chinese finger puzzle, harder you pull the tighter it gets. But getting this tool under the boot compresses it, so you can pull it out.

Can't do this on the Cruze, a blind boot, so they get plenty of dielectric grease. Not even sure if you can buy spare boots, looked this up, only come with the complete coil pack. And those springs to hang up in the shoulder of those boots leaving a nice large gap between that spring and the top electrode of the plug. There goes your spark. 

How about well over 35 years of designing and working with ignition systems, but had to be on a very strict budget. Did you know the entire 8 cylinder HEI distributor had to be provided to GM for six bucks! That included all the machine work on the distributor it self, the cap with the coil on it, all the electronics on the inside, plus 8 silicone spark plug wires with the boots installed. Other modules had to be done for as cheap as 69 cents. 

If you were even penny over budget, were in deep trouble. Then had to deal with OSHA, EPA, DOT, ERA, etc., and production problems.


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## Merc6 (Jun 8, 2013)

Wait, I thought anti seize also messes with the heat range and or the way the plug handles heat? 

Silicone on the boots goes a long way for these coil pack boots. Coil pack number 3 after only 1000 of being replaced got stuck in there and I had to gently pull out and pray it didn't break. I was going in to put fresh plugs after a new coil pack and to MP the springs and resistor as well. 

If you have a 2011, plugs are a cheap item to swap out seeing that the heat range changed on them after a few years if you ignore the BKR8EIX recommendations and stick to stock.


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## NickD (Dec 10, 2011)

Use to have a whole wide ranges of heat ranges, depending on your driving. City required hot plugs, highway, cold plugs. Another thing you can add to the history books.


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## jblackburn (Apr 14, 2012)

Merc6 said:


> Wait, I thought anti seize also messes with the heat range and or the way the plug handles heat? .


It does.


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## Robby (Mar 1, 2013)

Yer killing me here.

Torque is the increase in resistance to turning as each millimeter of thread gets side loaded because the fastener (plug in this case) is fully seated. (and why thread pullout becomes more likely due to overstress if a friction modifier is introduced)
The sealing area has little effect as far as assembled torque until the seal washer is fully compressed.

As far as carbon loading a plug thread......no lubricant will prevent that.

Rob


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## NickD (Dec 10, 2011)

> As far as carbon loading a plug thread......no lubricant will prevent that.


Ha, putting those kind of plus in my machine lathe and cutting off those worthless threads cured this.

Suppose we are driving this subject into the ground, ha, you do it your way, and I'll do it MY WAY!


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## Robby (Mar 1, 2013)

NickD said:


> Ha, putting those kind of plus in my machine lathe and cutting off those worthless threads cured this.
> 
> Suppose we are driving this subject into the ground, ha, you do it your way, and I'll do it MY WAY!


Although we agree to disagree, agreeably Nick, I should clarify why I continued.

I believe it is very important for us to not intermix our variations in service methods with the method recommended by the manufacturer.
By doing so, we are potentially putting other members property at risk if they embrace some 'not recommended' procedures.

I am not trying to get you to modify your methods.....like I said earlier, it is your car.
But it is, IMO, important to let the readers know that the method being discussed is a variation that you embrace.

Over the years, you have developed a feel for tightening a threaded anything without damage.....so have I, but neither you nor I can convey what that 'feel', feels like.......so, the readers, having not developed that 'feel' must defer to a torque wrench and be reminded the specification is for a clean, dry thread.

I apologize if you were offended.

Rob


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## NickD (Dec 10, 2011)

Can we find something in print on this subject? Ha, talked to many mechanics, next time they purchased a new vehicle, are going to take it all apart and anti-seize all the bolts. Key electrical rule is not to ever use dissimilar metals for conductivity, this rule is broken a zillion times. Also extensive use of unplated rolled cold roll steel bolts in aluminum castings. Put a wrench on these and the heads break off. Electrolysis and corrosion welds the threads together, ha, trade it in for a new vehicle.

Then which spark plugs have this special coating, even the ones made in China? Are any spark plugs even made in the USA any more? Contrary to what was stated, anti-seize actually decreases the thermal resistance between the plug and the head. Only a point contact is made at the top of the spark plug threads to the lower threads in the head, rest is a gap.

You can read a zillion articles on using aluminum castings in engines, lighter weight, better performance, etc. What you don't read is if they overheat they crack, or their thermal expansion is seven time greater than the cast iron block they are placed on requiring special head gaskets and throwaway torque to yield bolts.

What you don't read, is aluminum is adaptable to investment casting, iron requires sand casting, much smoother surfaces, a heck of a lot machining is required and a lot easier on the tools. Requires less than half the energy to melt this stuff, bottom line is that they are much cheaper to manufacture and far more profitable.

Here is an except from the Cruze shop manual, doesn't say not to use anti-seize or even to use it, nor the spark plug is a dissimilar metal to the aluminum head. Just doesn't say anything on this subject. And yes, I do use an inch ounce torque wrench when installing the plugs, and just pray I don't stripe the threads.

*Spark Plug Inspection* 

*Spark Plug Usage* 




Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions. Refer to Ignition System Specifications See: Powertrain Management\Ignition System\Specifications for the correct spark plug.
Ensure that the spark plug has the correct heat range. An incorrect heat range causes the following conditions:



Spark plug fouling-Colder plug
Pre-ignition causing spark plug and/or engine damage-Hotter plug

*Spark Plug Inspection* 














Inspect the terminal post (1) for damage.



Inspect for a bent or broken terminal post (1).
Test for a loose terminal post (1) by twisting and pulling the post. The terminal post (1) should NOT move.

 












Inspect the insulator (2) for flashover or carbon tracking, soot. This is caused by the electrical charge traveling across the insulator (2) between the terminal post (1) and ground. Inspect for the following conditions:



Inspect the spark plug boot for damage.
Inspect the spark plug recess area of the cylinder head for moisture, such as oil, coolant, or water. A spark plug boot that is saturated causes arcing to ground.

 












Inspect the insulator (2) for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes (3, 4).
 












Inspect for evidence of improper arcing.



Measure the gap between the center electrode (4) and the side electrode (3) terminals. Refer to Ignition System Specifications See: Powertrain Management\Ignition System\Specifications. An excessively wide electrode gap can prevent correct spark plug operation.
Inspect for the correct spark plug torque. Refer to Ignition System Specifications See: Powertrain Management\Ignition System\Specifications. Insufficient torque can prevent correct spark plug operation. An over torqued spark plug, causes the insulator (2) to crack.
Inspect for signs of tracking that occurred near the insulator tip instead of the center electrode (4).
Inspect for a broken or worn side electrode (3).
Inspect for a broken, worn, or loose center electrode (4) by shaking the spark plug.



A rattling sound indicates internal damage.
A loose center electrode (4) reduces the spark intensity.



Inspect for bridged electrodes (3, 4). Deposits on the electrodes (3, 4) reduce or eliminates the gap.
Inspect for worn or missing platinum pads on the electrodes (3, 4) If equipped.
Inspect for excessive fouling.
Inspect the spark plug recess area of the cylinder head for debris. Dirty or damaged threads can cause the spark plug not to seat correctly during installation.

*Spark Plug Visual Inspection* 




Normal operation-Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with additives.
Carbon Fouled-Dry, fluffy black carbon, or soot caused by the following conditions:



Rich fuel mixtures
Leaking fuel injectors
Excessive fuel pressure
Restricted air filter element
Incorrect combustion
Reduced ignition system voltage output
Weak coils
Worn ignition wires
Incorrect spark plug gap
Excessive idling or slow speeds under light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off.
Deposit Fouling-Oil, coolant, or additives that include substances such as silicone, very white coating, reduces the spark intensity. Most powdery deposits will not effect spark intensity unless they form into a glazing over the electrode.


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## spacedout (Dec 7, 2010)

Found 3 out of 4 of my plugs 1/4 turn from tight when I changed them in November(85,000 miles), one cylinder was 2 whole turns loose. The threads on that cylinder and plug where coated with baked on carbon. I also noticed the tick my engine had was gone with new plugs, however its been about 5,000 miles since and now its back..... suspect I may have a loose plug again. 

I changed the plugs and coil pack at that time due to a CEL misfire code under hard acceleration, flashing CEL came on while pulling out into traffic, stopped as soon as I left off the gas and never returned(limped the car home with a feather foot).


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## NickD (Dec 10, 2011)

Not only performance and fuel economy issues with failed spark plugs, but the O2 sensor detects oxygen in the exhaust, enriches the fuel that gets into the catalytic converter making toast out of it. And not exactly cheap to replace, talk about a self destructive device we drive. 

If you really want to read a controversial discussion on this issue, type in "anti-seize on spark plug threads recommendations".

You can over torque your plugs by 20% if you do! Is this also true of other torque specification? Like installing heard on a 57 Chevy 283 after a valve job, told to clean the bolt and oil them before torquing, the only correct way! Sure won't be correct if you installed rusty belts.

I read that 20% written by some idiot that doesn't even know what he is talking about. Granted a nickel plating does help prevent electrolysis, but did you know our EPA banned electroplating in this country. Was some time in the early 90's or late 80's. So done in China, even Mexico, but not here.

And how much nickel? About a quarter of a micron? Take on of these plugs and hold it to a very fine wire wheel on a grinder, one quick touch and its all gone! We live in a world of BS, get use to it. And spark plug manufacturers is only half of the story, what about the head its screwed into? And its not their job to give good reliability, its their job to sell spark plugs. 

I only use Permatex brand anti-seize, never did trust private branding, never will. 

Ha, ever worked as an engineer? Pestered by marketing, make it cheaper, by purchasing, we found this part cheaper, it doesn't meet spec, they buy it anyway, pestered by production, always problems on the line, pestered by the guys writing shop manuals, hired more for their literally and artistic skills, then added attorneys to the list, can print this, would be liable for warranty. Would hand them an 80 page document loaded with all the information, to lazy to read it. 

Had to burn the midnight oil to keep up with my own deadlines, stress is having a situation where you have no control over it, but have to learn how to take control. Many have died, shouldn't mention it, today I hit 77 years of age and still being a pest, LOL. No job worse than being a production manager, luck to hit 55 years of age.

But the instant I have the slightest hesitation in the engine, checking those spark plugs. Those misfires can cost you huge bucks. Call this experience, not hearsay.


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## Robby (Mar 1, 2013)

Happy #77 Nick!

Remember-----'It is always better to be seen, than Viewed'

Rob


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## Corny (May 15, 2017)

Have had a lot of vehicles over my 56 years of driving but never ran across the "loose spark plug" phenomenon before. After experiencing the mysterious ticking noise with my 1.4 2013, my dealer found a loose plug. Only 53K on them but we had them replaced, The cause is said to be expansion and contraction due to the heat. My guess is the turbo engine must burn hotter than naturally aspirated engines, hence the potential for more expansion and contraction. Living in a cold climate gives us more temperature extremes to boot.


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