Thermos

I just replaced my spark plugs at 105K miles (170K km) and below are photos of what all 4 of them look like. Does that look like normal wear or should I be concerned? The top electrode and surrounding area are covered in a bit of a whitish buildup and there is rusty-looking dust on the thread as well as rusty-looking runoff on the ceramic insulator. I looked at some spark reading guides online but none really fit what I'm seeing here..

PACman

From the threads on to the electrode looks typical. I remember my porcelain/ceramic part was still white; not brown like you have there.

Thermos

I just remembered that the original plugs were screwed in VERY tightly so maybe the rubber part of the ignition coil that covers that part was not fully on, causing that part to be exposed. All 4 of them had the same brown stuff on the ceramic part though

PACman

Plugs aren't suppose to be screwed in VERY tightly. I think it's in the area of 13-14 lbs ft of torque, which could be tightened or even over tightened by hand.

Simba91102

Those plugs appear perfectly normal; just what you're looking for. And though I agree with replacement (I changed mine out too at 110K), they look fine (though looks can deceive with parts like these).

The discolored threads are caused by the electrolysis created by the joining of two dissimilar metals (the steel plugs and the aluminum head). It'd obviously very minor and acceptable. The rust stains below the plug wire boot are caused by the corrosive action (obviously very slight) inherent when condensation develops and sits on the plug as it cools down (this is all over a very long period of time of course).

Thermos

Thanks Simba! I just needed some reassurance.
PACman - I realize that the plugs are not supposed to be very tight, that's why I was surprised. I basically hand-tightened them and then did another 1/2 turn with a wrench. That's what the plugs said on the box.

curls

The rusty coloration on the white insulator is known as "corona" and is normal.
Plug tips look normal and good.
Threads look slightly oxidated which could happen if the plugs were ever removed after being initially installed. NGK plugs use a special plating on the threads that acts as an anti-seize, but this plating is only good for the FIRST install.

Either way, if you can, buy a spark plug thread chaser and chase the threads with that just in case the oxidated threads on the plug have caused a slightly corroded thread in the head of the engine.

New plugs: Only the OEM recommended plugs from NGK. Laser Iridium. They are top-end plugs and worth every dollar.
Do NOT use anti-seize on the threads of the new plugs (explained earlier) but DO use dielectric grease on the plug boots to ensure a tight moisture-proof seal.

Tighten as per directions on the plug boxes - I believe finger tight (just with the extensions and socket, no ratchet) PLUS 1/2 - 2/3 turn with the ratchet.

Voila!

rtea2008

iTrader: (2)

this looks normal to mee