Blown Spark Plug?

[NSX Passion]

My NSX has a blown spark plug which stripped the head and broke the coil. My mechanic consulted 2 different Acura dealers which replied they have never seen this happen. We theorize that when the spark plug was replaced it was over torqued that fact and in combination with running the engine to high RPM probably caused this to happen.

Has anyone had this happen?

My mechanic is going to try to tap it as a last saving measure before needed to replace the head. Any ideas or thoughts?

Thanks.

 

[Briank]

Yes this has happened to other nsx owners, there is a repair method that does not involve replacing the head its called a helli-coil (SP).

See http://www.nsxprime.com/forums/showthread.php?s=&threadid=25778&highlight=spark+plug+coil

 

[DanO]

...running the engine to high RPM probably caused this to happen.

Can you please clarify? Do you mean running the engine TO high RPM, like 8,000 RPM or TOO high RPM, like 10,000 RPM? If it is the latter then maybe a compression check is in order for all cylinders.

DanO

 

[NSX Passion]

Yes this has happened to other nsx owners, there is a repair method that does not involve replacing the head its called a helli-coil (SP).

My mechanic is going to try this option. Can he do this without pulling the head?

Thanks for the thread reference.

 

[DanO]

Can he do this without pulling the head?

Yes.

 

[Cees-Jan]

This problem also known on accord, is caused by not tightened preveous spark plug, this causses leakage(not noticcable)and a film of carbon on the thread of the head after this it is very difficult to remove the plug resulting in damage to thread and not enough strenght for the new spark plug.

 

[NSX Passion]

It's Fixed!!!

Thanks for the advice from everyone. It was very helpful. The Heli-Coil tool worked and WITHOUT having to pull the engine. My mechanic also poured about 3 quarts of chemical inton the cylinder to flush any excess shavings. He said the exhaust valve on that cylinder must have been open because he did not pull 3 quarts back out- an added bonus in getting most of the shavings out.

What was learned... I bought this car used so it is hard to know its full history. I even had a full inspection from Mile High Acura in Denver. My mechanic checked the remaining spark plugs and discovered that not a single plug was torqued correctly! Every one under-torqued. That will not happen again on my cars.

Well my NSX is back to normal and running great!

JT

 

[hlweyl]

Glad the heli-coil worked for you. One thing that has always worked for me is to apply a small amount of anti-seize compound to the thread of the plug before installing, then torque.

 

[RC51NSX]

Glad the heli-coil worked for you. One thing that has always worked for me is to apply a small amount of anti-seize compound to the thread of the plug before installing, then torque.

Most torque specifications are for unlubricated threads, and if you torque lubricated threads to the specified torque, then you are overtightening them. I don't have my NSX manual here to see what it says about this.

 

[hlweyl]

Most torque specifications are for unlubricated threads, and if you torque lubricated threads to the specified torque, then you are overtightening them. I don't have my NSX manual here to see what it says about this.

That is true, but it is a risk vs benefit situation. When you are putting heads on certain cars, some head bolts need sealant on them, some don't. Torque specs do not vary or take in account the need for sealant so I'm guessing it shouldn't make that much of a difference. Personally I will still continue to use the anti-seize on all my spark plugs.

 

[titaniumdave]

I think torque specs take into account lubrication, one should not over-torque bolts by using lube. The biggest issue with torque is to make sure the torque spec is reached while the bolt is in motion. All surfaces have higher friction at rest(static) than when moving(dynamic) and the torque spec for bolts is for dynamic friction. If you go back and check a bolt you have torqued, it will always take more force to start it moving than it took to tighten it. For wheel lug nuts, I back them off 1/4 turn and re-torque them when ever I check them before a track day.

I never install a bolt in my car with out lube or locktite, a lesson I learned from a mechanic when I was young, has served me well for many decades. I always do the anti-seize on spark plugs and anything dealing with the exhaust where temperatures are going to cause bolts to expand and contract, tending to make them seize.

Glad the Heli-coil worked, the chips which end up in the cyclinder are soft aluminum, a good flushing will get 99% out, the rest should blow out as soon as you start the engine. I would flood the cylinder with oil before you start it to make sure any chips float loose the first time it is cranked.

 

[RC51NSX]

I think torque specs take into account lubrication...]

The following is typical of what you will find if you do a search for "torque specifications."

A Guide to a Selection of Torque Values
In preparing this guide to torque values the following basic assumptions have been made:

Bolts and nuts are new, standard finish, uncoated and not lubricated*
* If lubrication has been applied to the bolt and/or the nut (other than the normal protective oil film), multiply the recommended torque by the appropriate factor shown in the Lubrication Factor table. n.b. Antiseize lubricants can reduce torque required by approximately 20%.

I also lube bolts and spark plugs. I was just pointing out that unless your manual specifically says to lube whatever it is that you are tightening, then the torque spec given is for unlubricated threads.

 

[Cees-Jan]

Very good that it all worked out the easy way!!

When I fit the plugs of any car I don't lubricate, I always turn in by hand (without the wrench) till the seal reaches the head than I apply the torque on feeling, if you have mounted lots off plugs then it is quite easy to feel that you are sqeezing the seal ring (deforming) of the plug.

At Honda training they leared me never to lube wheel nuts, if this is done there is risk of loosing a wheel.

 

[titaniumdave]

At Honda training they leared me never to lube wheel nuts, if this is done there is risk of loosing a wheel.

I agree for lug nuts, just some WD40 now and then to keep them from rusting.