Do check and replace spark plugs frequently... (1 Viewer)

[hec4x4]

My old V8 just blew a plug. Yes, that is right. Blew a plug. The core of the plug ejected upwards. The thread was still in place. The inner core of the plug blew through the ignition coil, kind of exploded now.

If that happens, stand still, stop engine, do not try to drive home. Because you risk a short circuit on the wire loom, burning wires to the ignition rendering the cruiser dead. Completely dead. Stalled. No starter turns. Nothing. Then you need a new wire loom, and a lot of time to find that out.

In addition to that new coil that just blew up. And a new neighbour coil, as it may have gotten hurt by heat, so it disintegrates when you try to pull it up. Remaining 6 were ok with me.

I switched all 8 plugs at this point. No fun to see that happen again. They may have lasted around their servicable interval, but the other ones looked in very good shape.

So I suspect a manufacturing defect. Hence wrote to them, awaiting their reply.

The thread of the plug was burnt. Melted. So was the thread of the cylinder head. It was not possible just to mount another plug. Ouch. But my mechanic tried some helicoil stuff, and it seems to work. Saved me the cost of replacing the entire cylinder head. Phew.f

But the point is: Check your plugs. Replace if in any doubt. If misfire occurs, check immediately if a plug core is loose too. I did not dream to do that. Now I know. Just thought I'd share that knowledge.

Thanks for listening. Enjoy your day.

 

[caslim]

That plug looks 100 years old. How many miles were on it?

 

[sean2202]

What brand of plug was this? Looks like it may have loosened up like you say as the bottom threads are stripped but top is OK. I am assuming it is black because it was loose. Glad that helicoil worked. I would do a couple quick oil changes just to make sure any fragments from the helicoil fix that may have gotten in are removed.

I have heard mixed things about anti seize on plugs. Plug threads and aluminum heads are made from dissimilar metals. Now I use a couple drops of used motor oil. I was told the carbon in the used oil helps.

 

[mrbigboy]

This same thing happened with a coworkers 2005 LC. He however, is the king of owner neglect, and probably never changed his plugs until after the one blew out at around 190k miles. Helicoil fixed it for now.....

 

[Alaska]

Wow, that's impressive, I've heard of it happening before.
Good thing to know and to check on.
Thx for the heads up.

 

[Trunk Monkey]

I don't know that you need to throw out there that everyone needs to change plugs frequently. Your case is definitely a huge anomoly. Almost looks more like a coil wiring issue than a plug problem.

 

[weigellj]

Which Cylinder was this on? Just out of curiosity. Thanks

 

[hec4x4]

I don't know that you need to throw out there that everyone needs to change plugs frequently. Your case is definitely a huge anomoly. Almost looks more like a coil wiring issue than a plug problem.

Coil wiring result of plug blow up to smash it - you might note the flattened top of the contact nut at top of coil, it saw some pressure from resistance on its way up

Which Cylinder was this on? Just out of curiosity. Thanks

nr5 I think it is - standing in front of vehicle it is on the right side, second from the cabin

What brand of plug was this? Looks like it may have loosened up like you say as the bottom threads are stripped but top is OK. I am assuming it is black because it was loose. Glad that helicoil worked. I would do a couple quick oil changes just to make sure any fragments from the helicoil fix that may have gotten in are removed.

I have heard mixed things about anti seize on plugs. Plug threads and aluminum heads are made from dissimilar metals. Now I use a couple drops of used motor oil. I was told the carbon in the used oil helps.

Thx for hint around oil change.

I'll disclose the brand if I get a negative or no response from the manufacturer. IMHO, a plug should never behave that way. Hence I wrote them asking for their position on such a thing. If they assume no responsibility, I think that risk with at least that brand should be known to the market

That plug looks 100 years old. How many miles were on it?

Around 70-80K miles, some 100.000 kms. The rest of the plugs look just fine - for the time being you need to trust me on that - I cannot share a photo of those without disclosing the brand name, and I think they should have a chance to respond to me first, before I initiate what might become a s***storm I believe I have driven 150.000 kms on an earlier set, they seem to last forever at the end where they are supposed to wear out. Only do not trust that...

 

[04UZJ100]

Oh Jesus what brand plug is it? If it'ss not NGK or Denso it's on you.

Don't be that guy...

 

[hoser]

@hec4x4 After you realized it was misfiring, either by CEL or 'engine sounds funny', how long did you wait until you checked the spark plug... (in miles or time)?

 

[2001LC]

I agree with @sean2202 "I am assuming it is black because it was loose"

Fair quest on @hoser, I'd guess "some 100 Kms"

Carbon build up like doesn't happen over night, nor does it happen with plugs properly torqued in.

 

[hoser]

Any response from the spark plug manufacturer?

If I had to guess, it looks like the spark plug backed out. Exhaust gases made it way past the threads and burnt the plug like a burnt exhaust valve, eventually fusing the threads together. The electrode of the super heated spark plug failed, CEL displayed and ignored, eventually causing the center ceramic/alumina section of the plug to fail and shoot out. In the path of heat/destruction was the coil pack, wiring and even an adjacent coil pack.

 

[Sandroad]

IMHO, based on the condition of the plug, the manufacturer doesn't have any reason to be at fault. I think @hoser and others have it right and the plug was loose for a long time, leading to the failure. Since this is the first report of a plug failure like that on MUD (just the top of the plug blowing off), I agree with @Trunk Monkey that this is huge anomaly and no reason to replace plugs frequently (or blame the manufacturer for a loose/burned plug).

 

[hec4x4]

Oh Jesus what brand plug is it? If it'ss not NGK or Denso it's on you.

Don't be that guy...

Denso...

 

[hec4x4]

My old V8 just blew a plug. Yes, that is right. Blew a plug. The core of the plug ejected upwards. The thread was still in place. The inner core of the plug blew through the ignition coil, kind of exploded now.

If that happens, stand still, stop engine, do not try to drive home. Because you risk a short circuit on the wire loom, burning wires to the ignition rendering the cruiser dead. Completely dead. Stalled. No starter turns. Nothing. Then you need a new wire loom, and a lot of time to find that out.

In addition to that new coil that just blew up. And a new neighbour coil, as it may have gotten hurt by heat, so it disintegrates when you try to pull it up. Remaining 6 were ok with me.

I switched all 8 plugs at this point. No fun to see that happen again. They may have lasted around their servicable interval, but the other ones looked in very good shape.

So I suspect a manufacturing defect. Hence wrote to them, awaiting their reply.

The thread of the plug was burnt. Melted. So was the thread of the cylinder head. It was not possible just to mount another plug. Ouch. But my mechanic tried some helicoil stuff, and it seems to work. Saved me the cost of replacing the entire cylinder head. Phew.f

But the point is: Check your plugs. Replace if in any doubt. If misfire occurs, check immediately if a plug core is loose too. I did not dream to do that. Now I know. Just thought I'd share that knowledge.

Thanks for listening. Enjoy your day.

View attachment 1397507

So no response from manufactorer - Denso. Here are some pictures of another plug - same age, alle the other ones looked the same used but ok condition

 

[hec4x4]

@hec4x4 After you realized it was misfiring, either by CEL or 'engine sounds funny', how long did you wait until you checked the spark plug... (in miles or time)?

Some 80 miles/120 kms - behaved much like a coil eas shot, seen two times before, always on left/rearmost cylinder driving direction. Was on my way home some 300 kms, only made 180 kms of that before dead. In hindsight I'd stop immediately..

 

[hec4x4]

IMHO, based on the condition of the plug, the manufacturer doesn't have any reason to be at fault. I think @hoser and others have it right and the plug was loose for a long time, leading to the failure. Since this is the first report of a plug failure like that on MUD (just the top of the plug blowing off), I agree with @Trunk Monkey that this is huge anomaly and no reason to replace plugs frequently (or blame the manufacturer for a loose/burned plug).

A plug should not disintegrate like that, IMHO

 

[2001LC]

That bad plug looks like much more than 80 miles of buildup, more like ten's of thousands of mile driven while loose. The good looking plug pictured has some normal leakage, sometimes seen with high miles. Check gap and resistance to see if others are good.

Plug may have built more resistance as contact with head became increasingly worsened with carbon over time. Wouldn't the coil then given add amperage to compensate. At some point coil would overheat, just as seen when gap gets to wide. When to replace Ignition coils.

 

[hec4x4]

Any response from the spark plug manufacturer?

If I had to guess, it looks like the spark plug backed out. Exhaust gases made it way past the threads and burnt the plug like a burnt exhaust valve, eventually fusing the threads together. The electrode of the super heated spark plug failed, CEL displayed and ignored, eventually causing the center ceramic/alumina section of the plug to fail and shoot out. In the path of heat/destruction was the coil pack, wiring and even an adjacent coil pack.

Thanks for input. The thread itself was still 'mounted' and needed unwinding. The thread appear much more damaged at a minor part of circumference. I understand you suggest the plug thread was loose leading to this. I think all plugs sat in for past 3-4 years as-is, since theay appear pretty longlifed. One letting loose without exhaust melting stuff above it or blowing off coil or letting in smell of exhaust into cabin sounds impressive to me. But I am not the expert on such things, so I am listening in spite of some doubts. thx

 

[hec4x4]

That bad plug looks like much more than 80 miles of buildup, more like ten's of thousands of mile driven while loose. The good looking plug pictured has some normal leakage, sometimes seen with high miles. Check gap and resistance to see if others are good.

Plug may have built more resistance as contact with head became increasingly worsened with carbon over time. Wouldn't the coil then given add amperage to compensate. At some point coil would overheat, just as seen when gap gets to wide. When to replace Ignition coils.

All plugs replaced No more such fun