I've always used NGK bpr8es plugs gapped at .022.

But a month ago I replaced the protruded plugs for ngk br8es and also gapped them at .022.

Recently I noticed that after a couple hard pulls, then letting off on part throttle I pick up knock.

So this morning I decided to pull the spark plugs. For the most part they look pretty similar to what they have always looked like. Rich, yes and afrs are 11.3, 11.4 @ WOT.

Except for the glossy spots on the ground straps and the scent of coolant, this I have never came across.


I snapped a couple pics that may help, not the best used a cellphone.


In this pic, if you notice on the ground strap there is a very tiny dark spot. In
person it looks glossy in that spot. All plugs had this spot.

Sprk2.jpg?t=1318027618



And in this pic, might not be able to see it but what looks like fluid dried up. There is white spots. In person these spots run down past the electrode and porcelain. Kind of look like dry coolant spots.

Sprk1.jpg?t=1318028141



What got me thinking was the scent of coolant, I haven't noticed any significant coolant loss lately. And a month ago the plugs looked normal. Though I did notice the over flow needed to be topped off by a little.

I will be doing a compression and leak down test but thought maybe I could get some insight on here first.

Thanks!

 

coolant usually cleans up the chamber and the plug when it leaks into the cylinder. could the spots be tiny little pieces of aluminum? you can get that when you experience some knock

 

Yeah I've seen what coolant can do to a plug, wipes them clean or leave a chunky residue. Usually in severe cases.

The tiny spots are not aluminum. The tiny part on the ground strap is glossy, wiped it down and gloss is still there.

My nose is stuffed but there was still a slight scent of coolant, which is throwing me off.