Ignition coil plastic cover broken

[prwood]

High temperature RTV. The black stuff. You primarily concern is to keep moisture from eventually working it's way into the windings which will usually result in weak or no spark. Seal it up before that condition develops and it's none the worse for were. Note black tape is not a permanent/dependable moisture seal.

I'm picking this up after work today:

https://shop.advanceautoparts.com/webap ... gThaEbaoWn

Here are their instructions:

DIRECTIONS:
For best results, clean and dry all surfaces with a residue-free solvent, such as Permatex® Brake & Parts Cleaner.
Cut nozzle to desired bead size – gaskets are best formed using a 1/16" to 1/4" bead.
Apply a continuous and even bead of silicone to one surface, surrounding all bolt holes. Remove excess with knife at once. Assemble parts immediately. Do not squeeze out silicone by over tightening bolts. Re-torque will not be necessary.
Silicone dries in 1 hour, and fully cures in 24 hours, at 70˚F - 50% relative humidity. Allow more time in cold weather.
Replace cap after use. Clean hands with dry cloth or Permatex® Fast Orange® Hand Cleaner. Clean tools with non-flammable cleaning fluid.
NOTE: Not recommended for use on head gaskets or parts in contact with gasoline.

Since I'm using it to cover something up, and not to make a gasket, do I just draw a few beads of it across the exposed area and then smooth it over the surface with a rubber glove?

[abscate]

Sounds great. Get a good bead between the coil and the attach bolt which is the ground point for the coil, too. I still don't think there is much voltage in that metal, though

[mrbrian200]

On a side note I patched a VW DIS module (2 internal coil packs for 4 cyl engine) with this stuff. The car had developed a 'sputter' for the first few seconds on cool/damp mornings. I found a hairline crack running down one side of the module. I put a bead of this stuff over the crack and smoothed it over to a consistent 1/16 thick x 1/2 wide and never saw an issue with it again. The voltages on the secondary are so high that even atmospheric moisture becomes conductive and the spark current doesn't end going down the plug.

My suspicion with these coil packs getting weak/replacement interval approximately every 100,000 miles is that with repeated heat cycles atmospheric moisture eventually gets drawn inside. If you look at them closely they're not hermitically sealed--just at the top where the epoxy might give one that first impression. They're definitely not 'mil spec' in this regard. The broken side plastic you are patching would accelerate this moisture intrusion substantially. These are made by Bosch who seems to have a pretty good handle on deliberate design life failure to ensure continued revenue in the aftermarket/replacement market. For example: I can't think of any good reason for those slits to be there except to allow a somewhat controlled amount of moisture to degrade the core over time (which would result in a weak spark):

[abscate]

How did you make out with this repair, OP?

[prwood]

Quick update. I didn't make any changes to fix the ignition coil. I was able to start the engine. I've been driving it for three days with no issues so far. No visible or audible issues, and no codes thrown (misfire, etc). Today is humid and drizzly and there were no issues starting this morning.

I was looking at all of the ignition coils, and noticed that all of them actually have two small sections of this material exposed, apparently by design. I don't have my own photo of this at the moment, but you can try to visualize from the line I drew on this photo. When viewed directly from the top, there is a channel in the plastic on either side of the coil, and at the bottom of this channel, there is a gap in the plastic that shows a thin strip of the same metal I exposed when I cracked off the side of the coil.

Coil.jpg (96.98 KiB) Viewed 1333 times

This makes me lean more toward the theory that it's not a huge deal for this piece to be exposed.

I did receive the replacement coil in the mail from eBay. It looks to be in pristine condition, although I suppose a good external cleaning would belie any internal problems. If I'm not having any issues at the moment, I'm not sure it would be wise to replace it with an untested ignition coil... although I should probably swap it in so I can at least test it before my 30 day money back guarantee is up.

As far as the sealant, I haven't used it yet since I'm not having any issues with the coil as is. I guess I should use it anyway just to prevent excessive contamination of the underlying material.

[mrbrian200]

Actually, the exposure is a big deal: the core is composed of sandwiched plates of a ferrous metal. As moisture invades the layers become separated by an oxidized film which alters the core's electrical and magnetic properties - not for the better.

[abscate]

If you have the plastic cover on the engine there won't be a lot of moisture there - and it will be vapor - its hot under there.