Coil on plug exploded - NB8B

kiezon · Postby **kiezon** » Thu Oct 04, 2018 6:41 pm

Driving home last night and this happened.

Anyone care to share their input to why this has happened?

Rocker cover gasket has a leak
Spark plugs are 25,000kms old

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KevGoat · Postby **KevGoat** » Thu Oct 04, 2018 7:36 pm

Yikes!! Maybe a crack in the casing and a massive short to the rocker cover??

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Red_Bullet · Postby **Red_Bullet** » Thu Oct 04, 2018 8:20 pm

Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

kiezon · Postby **kiezon** » Fri Oct 05, 2018 11:19 am

Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

(Ding ding ding).

Correct from what I discovered. All plugs were loose, despite following the 'Hand tight then 1/4 turn' method.

The thing that concerns me now is the electrode from plug #4 is missing. Need an inspection camera to assess for damage.

Other than that, bought new plugs, heading over to Mania today for a new rocker cover gasket then a used set of COPs tomorrow.

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Red_Bullet · Postby **Red_Bullet** » Fri Oct 05, 2018 11:24 am

What brand plugs were they? I have read that Bosch plugs have a nasty habit of dropping electrodes. I swapped all my Bosch plugs out for NGK.

MX-5 torque settings link:

http://sandiegomiataclub.org/miata_tech/na/na_torque_specs.html

GR124 · Postby **GR124** » Fri Oct 05, 2018 11:47 am

Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

Well done RB, Top of the class for diagnosis. I would never have come up with that.

manga_blue · Postby **manga_blue** » Fri Oct 05, 2018 11:56 am

GR124 wrote:
Red_Bullet wrote:Taliban?

Loose spark plug? Compression pressure got past the seal? Substantial energy caused this, there is not enough energy in a spark to cause it.

Well done RB, Top of the class for diagnosis. I would never have come up with that.

Very clever, wasn't it? :beer:

Red_Bullet · Postby **Red_Bullet** » Fri Oct 05, 2018 12:01 pm

Never offer beer to a retired elevator industry tech support man, especially on a Friday. :lol:

hks_kansei · Postby **hks_kansei** » Fri Oct 05, 2018 1:13 pm

Now that it's been mentioned, it's pretty obvious too that there's a lot of carbon and crap that's been blown out of #4 too.

Red_Bullet · Postby **Red_Bullet** » Fri Oct 05, 2018 1:47 pm

Evidence my dear Watson.

kiezon · Postby **kiezon** » Fri Oct 05, 2018 3:45 pm

hks_kansei wrote:Now that it's been mentioned, it's pretty obvious too that there's a lot of carbon and crap that's been blown out of #4 too.

Nah, just oil from the rocker cover gasket.

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kiezon · Postby **kiezon** » Fri Oct 05, 2018 3:46 pm

Red_Bullet wrote:What brand plugs were they? I have read that Bosch plugs have a nasty habit of dropping electrodes. I swapped all my Bosch plugs out for NGK.

MX-5 torque settings link:

http://sandiegomiataclub.org/miata_tech/na/na_torque_specs.html

NGK BKR5E-11, I believe.

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manga_blue · Postby **manga_blue** » Fri Oct 05, 2018 4:06 pm

Red_Bullet wrote:Never offer beer to a retired elevator industry tech support man, especially on a Friday.

If you're retired then you can have a beer anytime you like.

Looking at the photos again it seems that the coil itself is not damaged, just all the bits that connect it to the #4 spark plug. It follows that you may not have to replace the coil. Instead you could just get the connecting pieces from another forum member whose coil has failed. Taking that further I think some creative work with a tube of silicone or RTV and some duct tape could put everything together again well enough for it to work until a replacement part arrives. At least that's what I would try.

RS2000 · Postby **RS2000** » Sat Oct 06, 2018 8:58 am

kiezon wrote:All plugs were loose, despite following the 'Hand tight then 1/4 turn' method.

Were the plugs new? If so, a 1/4 turn wouldn't initially compress the gasket washer enough to properly torque the plugs. On the side of the box for a new NGK BKR6E-11, it shows 1/2 to 2/3 turns.
For 14mm flat gasket seat plugs in aluminium heads, NGK say torque to 18 - 21.6 lbft