Spark Plug Insulator Is Brown

[privatealpha]

Hi everyone,

I changed the plugs today, just got the BCPR6es, gapped to .7/.8

However the old plugs, are noticeably brown on the insulator.

What causes this? Should I be worried that the same will happen to the new plugs?

Sorry for the large pic...

[mad082]

that's pretty normal.

[smithy85]

+1, its just that the metal 'nut' gets really hot and it inevitably transfers the heat through to the insulator, hence the brown is at the base. common.

Edited October 8, 2011 by smithy85

[jjman]

hey peeps,

similar thing. I changed my spark plugs on the weekend and just wanted to get some thoughts on the state of them as i have no idea about plugs and what they can indicate etc. (click on pic for larger view)

do these look alright? they are BCPR7ES plugs in a tuned 220rwkw RB25DET.

car runs like a dream and makes great power for the mods. compression test a while back came up essentially perfect, catch can gets no blowby oil in it etc etc

2 main things i also want to query/comment on for these plugs tho.

1]the tips have a fair bit of brown on them. Tho i did also run octane booster tabs which ive now learned arent good on sensors or plugs n turn plugs brown. is this it in action? -i only used about 2 tanks worth of boosted fuel. N a fair while ago (1000+ kms). otherwise do these tips tell a story? good or bad?

2]one of the spark plugs (second from the left) which was from cylinder 5 is browned around the socket section while all the others arent (nice n silver as per pic).

i have 2 possible causes-

- the rocker covers had leaked quite badly around cyclinder 5 & 6 and there was a film of oil making its way down into the spark plug holes, so might have got a coating on it n burned on like that.

- it did look like there was a possibility that the seal on the spark plug wasnt perfect as on one tiny part of the washer it looked like it had some carboning/burning so perhaps a bit of combustion gas forcing its way past...

any thoughts n comments people? im new to the whole spark plug reading game...

[central coast person]

Its called corona stain. It stains brown because of corona spark which is the gap between the insulator and nut and a spark traveling up the plug.

Go on google and type in NGK corona stain or spark and there is enough info for you

[jjman]

u sure? the corona stain is indicated as occurring on the insulator section, n not the hex/socket (metal) as on mine..?

If it is indeed a corona stain tho it would basically be the oil that had wept down in there had attracted to the hex section and burned on. No worries, and even less worries now that iv dont the whole cam cover seals and cleaned up all the oil that wept around.

anybody able to comment on the state of the tips?

Edited October 18, 2011 by jjman

[central coast person]

u sure? the corona stain is indicated as occurring on the insulator section, n not the hex/socket (metal) as on mine..?

If it is indeed a corona stain tho it would basically be the oil that had wept down in there had attracted to the hex section and burned on. No worries, and even less worries now that iv dont the whole cam cover seals and cleaned up all the oil that wept around.

anybody able to comment on the state of the tips?

Sorry, the OP has corona stain.

Yours looks like a manufacturing fault in the plug, the washer may also be the problem because it looks like its getting a lot of heat. Also people who pull there plugs off a lot dont understand but the washer cant be good for more than a couple of looks of your plug. Your tips are a nice orange-brown so nothing is wrong with the engine.

[mad082]

yeah nothing wrong with your plugs. when the tips, etc are a coffee colour then you aren't running too rich or too lean. as for the build up on the socket of the plug, could be what you said (leaking rocker cover, etc) but probably nothing too drastic

[jjman]

cheers again for the responses people.

Will check the No.5 when i change this next set of plugs for any similarity on the hex.

I looked closer last night and there is indeed a very slight corona stain on that No.5 plug too (nothing on the others) so likelihood is that is was the oil that seemed down in that area.

[StevenCJR31]

my plugs were brown on the ends due to the octane booster and (i believe) the injector cleaner i had put in the tank, no biggy

[jjman]

ha! give me some feedback on this then. My peice of shit bunky (1995 hyundai sonata- 2L 16 valve) started missing pretty hard recently so i decided to get in and change the plugs- see photos.

I think the rings of the valve seals are pretty rude as it drinks oil n farts black smoke as a habit.

check these plugs that came out. Also had lots of chalky residue on the top of the plug where the lead attaches (already cleaned off by this point tho as i didnt want any falling into the chamber as i changed em)- anybody have any idea what this is?

Edited October 31, 2011 by jjman