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Discussion Starter #1 (Edited)
In the midst of troubleshooting a misfire and was trying remove a spark plug. At first it was relatively loose, but the more I turned it the more difficult it became to turn to the point I was afraid of stripping the threads.

So here is the question, I was attempting this w the engine hot, just returned home from 60 mile commute. Does it matter if the engine is hot or should I hold off til the engine cools down?

I tried 2 cylinders and both reacted in the same fashion. I have never had them out during my ownership so 30k miles and 1.5 years. Therefore I cannot speak to how they were installed.

Thanks for the help!

05 330xi for reference.
 

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I always prefer to remove the plugs when cold.
If I were you, I would let the engine cool before going after the plugs again.
 

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A warm engine should make spark plug removal easier, so its good to try after a drive when its still warm. Perhaps try tightening back down and then loosening again, repeatedly, to see if you can make progress with out using much force on them. I usually feel a bit of resistance or "crunchiness" as you unscrew them, but never enough where I thought I'd strip threads.

Definitely back down if it feels wrong, don't force it. They can be a struggle to get out sometimes.
 

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In theory it should be easier when hot, but remember the plugs are steel and the head is aluminum so they will expand differently when really hot. If the steel expands more then the aluminum they will be harder to remove and doing so my strip the threads in the head.
 

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Aluminum will expand more than steel - cold maybe better. Back out as far as you feel comfortable squirt a bit of ATF around threads and screw in and out to work it in should come out easily then
 

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Aluminum will expand more than steel - cold maybe better. Back out as far as you feel comfortable squirt a bit of ATF around threads and screw in and out to work it in should come out easily then
Fwiw, I'd try it on a WARM but not HOT engine, not to get burned mostly but also in case that means the steel spark plug hasn't expanded too much vs the aluminum head. The ATF or penetrating oil idea is a good one.

OP,

There was a long thread about stubbon spark plugs a while ago:

https://forum.e46fanatics.com/showthread.php?t=1234006
 

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Discussion Starter #7
Thanks for the replies. I waited a bit and was able to retorque the original plug. (I gave up on removing them for the night bc I need to use the car again tomorrow.) The second plug was a bit more stubborn so I let it go. Going to try tightening it again now. If I get it back in all the way tonight ill try removing again tomorrow or Wednesday when it's just warm.

@LeverThis, I did try the working the plug in both directions and it worked for awhile loosening it, but eventually it got to point that it got tight w/ 1/2 " ratchet. So I threw a torque wrench on it set at 18 ftlb. It was uncomfortably tight and way more than 18 ftlb.

After walking away I pondered the same as you guys mentioned with the metals expanding at different rates potentially causing issues. It was just very odd for the plug to feel borderline loose at first turn and become tighter as I loosened it. It wasnt the normal feeling of a bolt or nut breaking free and becoming easier to turn.

So the suggestion of atf to aid in removal of plug, are you guys referring to auto trans fluid?

Thanks again for the support.

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Discussion Starter #8
Everything is back together for now. The second plug was uncomfortably difficult to torque down. The thought of stripping the aluminum head is absolutely miserable.

Keep the insights coming and I'll report back what happens over the next few days.

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Wondering if any of those holes have had a thread repair gone bad that's causing the problem? I don't think the metal expansion is the issue, if that was an issue, then this problem would appear anytime you removed the plugs with a hot engine to do a compression test. At this point the only way to know would be to pull them out.
 

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There also might be dried burnt oil in there. I've had the valve cover seals weep oil into the spark plug tubes and make plug threads grimy/sticky to get out. I was able to get them out on a cold engine. There was resistance the whole way out but they came out.
 

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Everything is back together for now. The second plug was uncomfortably difficult to torque down. The thought of stripping the aluminum head is absolutely miserable.

Keep the insights coming and I'll report back what happens over the next few days.

Sent from my SM-G950U using Tapatalk
Yes, ATF as in auto transmission fluid. Its a good substitute for penetrating fluids/oils in general if you have no PB Blaster, Kroil, etc., on hand. A 50/50 mix of Atf and acetone is basically a homemade penetrating fluid and is actually pretty effective. Any penetrating fluid should work though.

Try an incremental approach. Unscrew plug until it tightens up, spray Liquid Wrench, etc, on threads. Tighten loosen back and forth. If still stuck, then tighten back up and let soak overnight. In the morning, more liquid wrench plus tighten and loosen. If still stuck, clean up all the pf spray and run engine for 10 minutes to warm up a bit and more tighten and loosen. Let it cool down and start over. Some variation of this routine should get it out safely at some point.
 

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I've always done plugs when the engine is cold.

And people get flamed for suggesting a little anti-seize on the threads when installing plugs.
NGK, who makes the plugs, says to not use anti-seize which is where the recommendation comes from.

You can still use it, but need to be super-careful when it comes to torquing them down (same reason why anti-seize isn't recommended on wheel bolt threads).

What the OP is experiencing is unusual. I pulled original plugs at 110K miles with no issues and that was without any anti-seize from the factory.
 

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Removing plug with hot engine could strip the softer hotter threads. Cold head has stronger threads.

Old plugs might have the protruding threads covered with burned oil and hard carbon; hence it broke loose then jammed by the mentioned dirty threads.

Go slow easy back/forth with lube oil, and best of luck.
 

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In the midst of troubleshooting a misfire and was trying remove a spark plug. At first it was relatively loose, but the more I turned it the more difficult it became to turn to the point I was afraid of stripping the threads.

So here is the question, I was attempting this w the engine hot, just returned home from 60 mile commute. Does it matter if the engine is hot or should I hold off til the engine cools down?

I tried 2 cylinders and both reacted in the same fashion. I have never had them out during my ownership so 30k miles and 1.5 years. Therefore I cannot speak to how they were installed.

Thanks for the help!

05 330xi for reference.
May I suggest you use a torque wrench to undo the plugs to reduce the risk of stripping them? It's a good idea and common practice when removing glow plugs from diesel heads, for example, which are notorious for breaking. Spray penetrating fluid in there over night. Work them back and forth as you go.
 

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Discussion Starter #16
May I suggest you use a torque wrench to undo the plugs to reduce the risk of stripping them? It's a good idea and common practice when removing glow plugs from diesel heads, for example, which are notorious for breaking. Spray penetrating fluid in there over night. Work them back and forth as you go.
I'll try the various methods suggested by all. The above by Ray is what I did when the abnormalities began. I knew they were tight with the ratchet so I set the torque wrench for 18 ftlb and tried loosening w/ it. It clicked immediately. That's when I decided to abort.

I dont feel they are stripped at this point since I was able to torque them in last night. Car ran fine this morning.

The suggestion regarding exposed threads being gunked up with carbon is a distinct possibility since I have no idea how long they've been installed.

I have many a penetrating fluids available and will use one of them tomorrow when I attempt this again - when the engine is cold!

Thanks again.

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I'll try the various methods suggested by all. The above by Ray is what I did when the abnormalities began. I knew they were tight with the ratchet so I set the torque wrench for 18 ftlb and tried loosening w/ it. It clicked immediately. That's when I decided to abort.

I dont feel they are stripped at this point since I was able to torque them in last night. Car ran fine this morning.

The suggestion regarding exposed threads being gunked up with carbon is a distinct possibility since I have no idea how long they've been installed.

I have many a penetrating fluids available and will use one of them tomorrow when I attempt this again - when the engine is cold!

Thanks again.

Sent from my SM-G950U using Tapatalk
The carbon build up is a strong possibility. Perhaps you might slacken them off leaving them loose and spray some SeaFoam in there see if it will travel past the threads and onto the carbon build up help dissolve it.
 

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Removing extremely reluctant spark plugs is unnerving. There's always that question in the back of ones mind "Am I stripping the threads?"

When we're presented with such, we usually loosen the plug a turn or two. Spray penetrating oil down the hole and let sit for 5 min. Then turn in a turn or two and wait again. The idea is to get the penetrant into/through the threads.

How much should you force it out...? It's an experience thing that can no way be translated to you in typing. :>((

Using a torque wrench in reverse is generally not a good idea.
Almost any fastener will require more torque than installation once it's set.
Torque wrenches last longer if only used for tightening purposes. Higher end torque instruments such as some of the ones in my shop only work in one direction for that reason.

BTW, Yes I'm a member of the apply anti-seize to spark plug threads. Always have been.
BTW some MB cars recommend removing spark plugs on some of the "Service B" if the car has time but low mileage for the reason you are now confronted with.
 

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Discussion Starter #20
Removing extremely reluctant spark plugs is unnerving. There's always that question in the back of ones mind "Am I stripping the threads?"



When we're presented with such, we usually loosen the plug a turn or two. Spray penetrating oil down the hole and let sit for 5 min. Then turn in a turn or two and wait again. The idea is to get the penetrant into/through the threads.



How much should you force it out...? It's an experience thing that can no way be translated to you in typing. :>((



Using a torque wrench in reverse is generally not a good idea.

Almost any fastener will require more torque than installation once it's set.

Torque wrenches last longer if only used for tightening purposes. Higher end torque instruments such as some of the ones in my shop only work in one direction for that reason.



BTW, Yes I'm a member of the apply anti-seize to spark plug threads. Always have been.

BTW some MB cars recommend removing spark plugs on some of the "Service B" if the car has time but low mileage for the reason you are now confronted with.
Summed up perfectly. I ordered the syringe suggested above to apply the thread lubricant. Agreed on the anti-seizure as well, always apply a small dab.

MrMCar, any thoughts on the temperature of the head and plug making a difference for when to remove/install the plugs?

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