Crumbling Insulation on Coil Connector Wires

I am the original owner of a stock Gen 2, 2010 TRD 4.0L 1GRFE The truck currently has 198,600 miles and is needing some preventative maintenance. I have 6 qts of Valvoline

$29 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 high performance for the transfer and diffs but decided to start with replacing the plugs. Last changed at 160K. I started with the drivers side since it can be a little more difficult and I had a fresh batch of patience and the engine was cold. Good choice. When I got to the passenger side plugs 1 & 3 would only move a half turn then pretty much locked up. So I took it for a drive to get some gas for the mower and a losing Mega Millions ticket. After a lot of turning in and out I was finally able to remove both plugs. Gapped new

$9 90919-01235 Toyota Genuine Spark Plug

90919-01235 to .041” and torqued to 15 lbs. During tool clean up and final inspection I noticed some bare wire at the base of the connector for plug #1. When I wiped off some grease and grime the insulation crumbled off the conductor. GASP ! The more I touched it more easily flaked off. The boot around the wires was distorted, hard and cracking. Extremely over heated. The drivers side were round and flexible. I cut away the entire cover. Only a small amount of the insulation came off of pin 1 black/red but at least 2” came off of pin 4. Is it supposed to be yellow/black or green/black? The wire is discolored. I noticed the boot on plug 3 was also distorted. When I cut away the boot the insulation on the wires were even worse. The conductors all look fine. Can I just cover these bare wires with some heat shrink tube? I have some PVDF which is rated for 350 degrees. Abrasion Resistant; Acid and Alkali Resistant; Fuel and Oil Resistant; High Heat Resistant; Solvent Resistant. I also have some fiberglass and foil tube shielding rated for 400 degrees. Will this be an acceptable band aid until I can figure out what is the cause of this problem and a solution? This is my only vehicle.

 

Yeah, I would think your PVDF/Kynar heat shrink tubes should be perfectly fine for a band-aid.

 

Do you have a picture? They only issue I see with heat shrink is how you will get it on the wire? Assuming you will de-pin the connector install heat shrink and then reassemble

 

Pics are in the word doc attachment...

 

Ahh. I dont click on random attachments / file types unless I know what it is

 

.docx is a word document...I get it tho, weird way to post the pic...

but yeah OP has removed the wires from the coil pack connector plug.

 

Wow thats a lot of damage for a 2010 - more than normal aging it seems..

I still think heat shrink will work fine. Only thing I would be concerned about is that far rear cylinder. If the insulation is compromised all the way into the factory split loom you'll have a lot more work on your hands

 

I'm going to have to dig further down into the harness to see if there is additional damage. What would cause these two wire sets to lose the insulation? And only on pins 1 and 4 for both. Is it just a coincidence that these two plugs were extremely difficult to remove or could it be a sign of another problem? If i remember correctly they were a problem to remove previously. The rear cylinder 5 seems fine. the boot is soft and pliable.
I am surprised and glad the bare wires did not short out.

 

Some kind of corrosive or high-solvent fluid being dripped/spilled on just those portions of the wires at some point in the recent or distant past? Brake fluid, brake cleaner, ATF, etc?

 

Each wire set is covered with one large black tube and taped to the main harness. The only exposed wires is where the black tube meets the base of the connector. Look at plug #5 on the left. It still has what i call a boot to protect the wires. Plugs 1 & 3 had the same covering but it was hard and distorted, appeared over heated. I had to cut away the black tube before i could see the total damage to the wires. I'm thinking it was caused by long term excessive heat since the wires pretty much sit an inch above the cylinder head. I de-pinned the connectors and covered each wire with two layers of 375 degree temp heat shrink tube. I ordered 1/2" foil wrapped fiberglass tube shield. A 4' section from Grainger only cost a little over $10.00 I should pick it up tomorrow and get this project wrapped up, pardon the pun.

 

how do the pins look? any corrosion at all on either side?

 

Pins are clean with good connection to the wires. Runs great. Curious what the heatshrink tubing will do after a hot day hauling the boat to the lake. Only other concern would be moisture wicking up the heat shrink tubing.