spark plug corrosion.

[coolride]

I pulled the coil on #2. Just because it's easy to reach and I'm learning my way around. There's a collection of red debris that settled around the sides of the spark plug.

The camera wouldn't focus. It's a reddish fine crystal (like sugar) and it breaks up into a fine powder if you rub it between your fingers. (way down there next to the plug)


There's also some reddish stuff on the collar of the rubber coil boot. Does anyone know what's going on here?


The plug also has some problems. It's an ACDelco 41-981, with discoloration and corrosion. This is maybe an original plug and I doubt that the coil has ever been removed either (140,000 miles.)

 

[mrrsm]

The phenomena you are describing has two possible origins:

(1) If the Spark Plugs are located in the 5th or 6th Cylinders... and the Weather Strip around the top of the Coil On Plug (COP) Seal has been compromised ...AND... the Weather Strip running the length of the Plastic Fascia between the Hood and the Firewall has been compromised... Heavy Rain can drain down inside of the Spark Plug Well ...and cause Rust and Corrosion to set in at the junction of the Ceramic Insulator and the Plated Hex Body of the Plug.

As the Water gradually "Boils Off" from the build up of concentrated Engine Heat, the residue of the rusted base metal and corroded metal plating is what is left behind as a 'friable' powdery ring that collects on adjacent areas trapped inside of the semi-sealed Spark Plug Wells.

(2) If the "O" Ring style Grommet Valve Cover Inner "O"Rings lose their seal... Engine Oil propelled by Gas Blow-By can force Motor Oil into the Spark Plug Wells...where the Heat of the Engjne Head Concentrates around the base of the Spark Plug ...and literally Cooks it into a "Fried Chicken Brown" ring around the interface between the Ceramic Insulator and the Hex Body of the Spark Plug.

Based upon your excellent images... My Money is on (1) as being the source of the issue. :>)

I think it was @Mounce (CORRECTION ... It was @christo829 who discussed the Cowl Seal Solution) and solved this problem as it was covered in THIS Thread:

Water Sitting In Sparkplug Holes

Working on my 06 Trailblazer EXT with the I6 engine I found water sitting in (starting at the front of the motor) cylinders1,2,and 3. I found dried up water deposits before in cylinders 1 and 2 but not water. Any ideas on how to stop this ? The coil pack was pushed down all the way and last...

gmtnation.com

 

[coolride]

I think you're right MRRSM. It doesn't look like cooked oil at all. I thought that maybe it was old and dried up (crystallized) lube that was applied onto the sealing surfaces of the soft rubber part of the coil assembly.

I just used the shop-vac and the air compressor, simultaneously, to blast that strange dust (precipitate?) out of the spark plug recess. Here's a look at plug #3 (I cleaned the previous plug before photographing but this one's untouched.)


A little water, dissimilar metals, and electricity (galvanic corrosion time.) Looks like maybe the chrome plating and the steel were entering into solution and then crystallizing out, as the water boiled off.


I can just sneak a 45 thou gauge into this gap (so it's probably 44.)

 

[Mounce]

Don't gap your new plugs if/when you replace them. Can break the iridium tip off the electrode, they come pre-gapped. Also use only the ACDelco replacements which are 41-103's on the i6. Can be found for a good deal on ebay/Amazon.

 

[Mooseman]

Just be careful about counterfeits, which seem to be prevalent on eBay and some on Amazon. We have a thread on it somewhere here.

 

[coolride]

Any idea why I don't have 41-103's on there now? I have 41-981's.

 

[Mooseman]

That's the old part number. New one is 41-103

 

[Blckshdw]

Any idea why I don't have 41-103's on there now? I have 41-981's.

Those were your original plugs, I had the same thing on my 05, when I changed the plugs a few years ago.

 

[coolride]

Check this out. Cylinder #one coil boot actually has a high water mark.


The space around plug #1 is packed with mystery powder. I was shocked.

 

[coolride]

And plug #4 (not great.) Those shiny little flecks in the threads are aluminum.


I pulled off the rubber coil boot and saw a bead of water on the coil electrode, then I looked over the spring and found this. (More water, and way up inside the coil.) Whatever...


I think that every bad plug had a coil boot that looked like it was installed wrong. The thin walled area of the boot (outboard of the small slot) , was jammed up and away. (Poor installation.) Below is the damage to plug 4's boot. Number 5 looked perfect and it's boot didn't have this installation defect.

 

[mrrsm]

And to help with preventing any further Weather-Water Intrusion onto the level Upper Engine Surfaces... Amazon sports a Very Nice Assortment of Weather Seal Stripping for Engine Hoods and Cowls that you can choose from to keep this problem from plaguing those "Poor Plugs" ever again:

Amazon.com : hood cowl

I'd also like to also suggest getting your hands on a can of 3M (Minnesota, Mining & Manufacturing) #80 Spray Rubber Adhesive that WILL specifically Bond additional problem areas such as surrounding rubberized Door Seals as well, ensuring a REALLY Sticky and solid adherence level:

3M 80 Rubber and Vinyl Adhesive Spray, 24 oz Aerosol Spray (Net Weight 19 oz): Amazon.com: Industrial & Scientific

3M 80 Rubber and Vinyl Adhesive Spray, 24 oz Aerosol Spray (Net Weight 19 oz): Amazon.com: Industrial & Scientific

www.amazon.com

 

[coolride]

The question: Why did plug #1 have the worst water damage, and plugs 5 and 6 had the least?

The engine sits low at the firewall and plugs 5 and 6 sit directly under the leaky firewall weather strip. I expected to find the worst corrosion under the weather strip, but the worst damage was at the front (plug 1.)


Here's plug 6. Looks good (as did plug 5.) I tried removing it last night; had it backed off 1/4 of a turn and then it froze solid. I was like "dam" it's welded in there. After flooding the hole with WD40, I said a prayer and hit the hay. This morning it broke free and then it backed out (thank you Jesus.) Again, plug 6 is in good shape (doesn't make sense.)


This side terminal electrode (iridium?) is worn away. The gap is 52 thou. Plugs 1-5 had good electrodes, and gaps that were consistently about 45 thou. I won't reinstall this plug.

 

[Mooseman]

Center electrode is worn as well. That tip should be much longer.

When you get the new plugs, DO NOT GAP THEM. They are pre-gapped and trying to gap them might damage the tips. A little anti-seize would be good, as you saw. Also, the engine must be DEAD COLD when doing this as the threads in the head might get galled.

 

[coolride]

Is the new plug (41-103) designed different that the old plug?

My original plugs have a very pronounced extra "nipple" on the side electrode. The new plug has a very flat and traditional looking side electrode.

 

[TequilaWarrior]

Is the new plug (41-103) designed different that the old plug?

My original plugs have a very pronounced extra "nipple" on the side electrode. The new plug has a very flat and traditional looking side electrode.
View attachment 90904

Looks right... a little flat, but right. Does the other end of the plug - where the wires go on (can't remember its name, sorry), have 3 white dots on it? If so, it's genuine. If it's genuine, and new - install it without touching the gap.

 

[coolride]

Yes, it has three white dots. Gap seems preset at about 42 thou.
(Terminal nut I believe.)

 

[mrrsm]

To Answer the Question posed in Post #12 as to "Why is there MORE Corrosion in the #1 Cylinder Well vs. any Others...".

Water weighs around 64 Lbs Per Cubic Foot and always seeks its OWN Level for the Lowest Possible Settling Point. As you pointed out...the Engine sits on the Motor Mount "Bulbs" tilted slightly downwards at the nose of the SUV due to the natural "Rake" of the GMT360 Chassis Design. The Rain Water may be entering at Higher Volume of Velocity where the Rubber-to-Plastic Cowl Seal mates up... But then it rapidly flows forward following the downward angle ...pooling in greater amounts around the Cylinders closer to the Front of the Engine Block Valve Cover and therefore it has a much better chance of migrating down into the Lead Spark Plug Wells.

One other observations about the "Tip" of the Old Spark Plug is that once the very thin coating of either Platinum or Palladium either wears off or gets damaged from being "gapped" with harsh contact from Feeler Gauges... the underlying Mild Steel Metal Tips is exposed to conditions where the Oxygen contact is present at 10.5:1 Atmospheres along with Water as a direct By-Product of Incomplete Combustion... rapidly accelerating its Rusting and Destruction from High Voltage Electrical exhanges ...in the Millions if not Billions. NOT touching those Electrodes is always preferred to 'gapping' Factory Plugs that come with a Warning NOT to do so.

 

[coolride]

I've only wrenched on the TrailBlazer, on and off, for a couple weeks (and I have no manuals.) I google searched the cylinder order and what I learned (and this might be wrong) is that #1 is by the radiator and #6 is against the firewall.

In the distance from the front edge of the coil boot hole on #1 to the back edge of the "boot hole" on #6 (about 22 inches,) the valve cover drops about 1 & 1/4 inches.

Water should flow from the front of the valve cover, toward the back. I think that's what you're saying. What confuses me is, the plugs at the low point (#5 and #6) had the least corrosion. And plug #1 (the high point) had the worst. I expected the high point to be the driest, and also to have the least corrosion.

 

[mrrsm]

You can get the Very Best Service Manual... EVER ... for your SUV Right Here at Good Old GMT Nation, courtesy @Mooseman who has created a Library of GM OEM Digital Service Shop Manuals that should include your particular version by Year-Make-Model. Just Visit and Download the right one for FREE via THIS Link:

Need service manuals? Get them here!

********* Please note that the FireFox browser has issues with the password handling and that these downloads are not under HTTPS, flagging them as security risks. Chrome and Edge work fine once you allow the download. ********* ATSG 4L60E Manual 4L60E Rebuild Manual 2005 GMC Envoy XUV...

gmtnation.com

 

[Mooseman]

Maybe just that particular coil had a bad seal? I think 2006+ coils were supposed to be better for sealing on the new aluminum valve cover.

 

[coolride]

There's also a weather seal at the front of the hood. Worth considering maybe. Mine was embedded with dirt and grim.


Look how dirt, stuck to the seal, wore away at the core support paint.


This driver's side front body brace has a sharp corner, and the rubber seal rests against it (see the wear mark at the sharp corner.)