Plug #2 Mystery

[Schon '02]

It’s been almost four years since acquiring the ‘02 from a trusted friend and the car has been trouble free other than a balky temp gauge (bad ground). The car drove well without any glaring issues, but I can’t say that I had any relative bench mark to compare the seat of the pants feel for the upgraded engine (Weber’s, cams, and headers). It was past due  to explore the top end for the first time, so with a long weekend at hand, I checked the valves and the plugs.
 

The valve train looked very clean. The valve lash all checked out at 0.008 for the 292 cams… the plugs all checked out as well with NGK BP6ES’ at 0.040. But the #2 plug was hard to pull as if it was cross threaded. One photo shows a small bit of substance between the crush washer and the shoulder of the plug… another shows something down at the bottom of the well… and the third shows what was scraped out (a hard, brittle, reddish material). Upon replacing the plug, I went heavier than usual on the anti-seize and pulled the plug back out whenever there was resistance to check the thread-depth. It took several passes to eventually get the plug to screw in smoothly to the bottom, so I could make sure it was seating properly and then torqued.

 

The engine now seems more responsive on throttle than before (barely touch the pedal and there’s no hesitation on revs) and seems to have more power on the road. I checked the plug well after cool down and all looked normal and dry. 
 

So, thoughts on what that stuff was in the plug well and why it might have found it’s way down there?

 

 

 

 

 

 

 

 

[tzei]

Bakelite debris from plug "boot"? Color sure looks the same.

[Schon '02]

The material down in the well had to be scrapped off the head. It wasn’t loose. It appeared to be an epoxy of some type that was fluid before it set up. 

[visionaut]

Bakelite is a thermoset phenolic resin. (the 1st synthetic plastic). Great electrical resistance properties, but it’ll re-melt if hot enough…

[Lorin]

Sounds to me like the plug was slightly seized in the head which slightly deformed the threads in the head upon removal. 
 

 

[Schon '02]

1 hour ago, visionaut said:

Bakelite is a thermoset phenolic resin. (the 1st synthetic plastic). Great electrical resistance properties, but it’ll re-melt if hot enough…

Would the temp at the base of the plug be hot enough? The current wires have a silicone boot. Perhaps the previous wires had a Bakelite boot and chipped upon removal, and the PO or mechanic didn’t realize it when he put in the plugs, and the plug wasn’t fully seated when it was tightened? 

[tzei]

That seems plausible.

[TobyB]

It's probably too late now, but whenever you pull the plugs,

keep them in order and compare the coloration and pattern on the tips.

 

If one cylinder is behaving differently, then you'll see it.

 

My vote is that you had/ have a marginal plug wire, and that

removing/reseating it/ them improved things.  The M10 is 

very hard on plug wires, relative to most engines.

 

As to the goo, you can easily drop anything into a plug well, and if 

it's a soft plastic, there you are.  

 

As to the binding, the nose of the plug protrudes slightly from the head,

so when the plugs are 'bindy,' it's best to immediately drip a bit of aluminum

cutting fluid into the well,

(it reduces the chance of galling a LOT)

and work the plug back and forth a bit to get the fluid

coating the threads,  Then you can work the plug in and out, accent on the

out, and it'll eventually come free.

That's why I always use a judicious amount of aluminum anti- seize on the plugs.

It helps prevent them from sticking, but when they do, it almost guarantees 

that you won't kill the threads working the plug out.

 

And yes, if the plugs work loose, it can melt the plug boots.

 

t

 

[Schon '02]

Thanks guys! Feeling better that whatever was in the plug well was incidental and not some means to deal with an issue. 

[Mike Self]

Those brown pieces sure look like bits of spark plug terminal.  Those terminals get brittle as they age, and pieces will break off the open end, often when installing or removing.  One of them could have prevented the plug from seating (and sealing) properly, causing the plug not to function as it should.   

 

Whenever I'm gonna pull a spark plug, I examine the terminal carefully to see if there are any missing bits.  If that's the case, I blow out the spark plug well with compressed air before removing the plug so those bits won't fall down into the cylinder.

 

mike

[visionaut]

2 hours ago, Schon '02 said:

Would the temp at the base of the plug be hot enough? The current wires have a silicone boot. Perhaps the previous wires had a Bakelite boot and chipped upon removal, and the PO or mechanic didn’t realize it when he put in the plugs, and the plug wasn’t fully seated when it was tightened? 

I dunno. It’ll also char if burned., but it’d have to be quite hot.  So will rubber. Maybe a little oil, dirt, and bits of burn/broken old plug wire ends can melt into an epoxy-like residue… Could have even gotten some in the threads causing the issue with the plug.

The fact you’re running better now/after is likely due to you getting the plug right and a better spark connection…

Edited January 22, 2022 by visionaut