DIY: MkIII VR6 Coilpack repair

[kai_h]

This writeup was originally posted to an old blog many years ago and now I've discovered VWWatercooled, and the DIY thread for MkIII's, I've moved it all over here. I did this repair in May 2006 and the repaired coilpack is still going strong to this day.

The coilpack failed a while back on my 1996 Golf VR6, and I just couldn't bring myself to pay well over $500 for a brand-new one, not after just having forked out over $300 for a new auxiliary coolant pump, so I did what any self-respecting tinkerer would do and hacked one together from broken parts =)

Here's a photo of the original one - you can see that the terminal has broken right off it, such that I can't even see any metal contacts inside that would have connected with the terminal. It seems that the inside of the coilpack is filled with expanding foam, and when the terminal broke off, the expanding foam came out and covered everything. The terminal was so loose that simply unplugging the ignition lead for cylinder #1 was enough for the whole terminal to break off!

Here are the old and new (second-hand) coilpacks side-by-side. I got the new one for $100 as it had one boot broken off. Strangely, it was also the terminal for cylinder #1 that had failed on this one - anyone else out there with a broken coilpack, let me know if it was also cylinder #1 that failed for you.

Having the broken terminal from my original coilpack, I was easily able to chip off the black epoxy leaving just the plastic boot, that I then epoxied onto the new coilpack.

You can see in picture #4 the broken boot...

Here is a picture of the broken coil area on my original coilpack. There is no visible metal, I can't see any electrical connector. I suppose the expanding foam it's filled with is so that if (when) it fails, it fails safe and covers the high-voltage areas with an insulating foam.

Here's how to take the pack apart, and put it all back together, hopefully working, and hopefully in better condition than when it was removed.
First, remove the plastic cover/cable guide on the top - it should just unclip:


Next, undo two screws on the back of the coilpack


Then, there are four locknuts that need to be undone. I can't remember the size, however they are metric, not imperial sizes. Maybe 6mm?


After undoing these nuts, it all comes apart quite easily


Here's the control module, removed from the rest of the unit:


Here's the rear of the coils:


Here it is, all in pieces, ready to be washed and reconditioned:


continued...

[kai_h]

Before applying the JB-Weld, I washed the whole thing in hot, soapy water, and then dried it thoroughly. Next, I wiped down the area around where the boot glues on with acetone, to remove any traces of contamination:


Here's the high-temperature silicone I used - Loctite blue:


I mixed up a batch of JB-Weld and glued the boot back on over the terminal. Even without the epoxy, it was a snug fit, and with the epoxy on there it went together very well and seemed to make a good seal:


I did some research on JB-Weld, having been told it was the stuff to use, but I wasn't too sure of the availability here in Australia. I saw an aussie place selling it online, but for something like $27 with $8 postage. I then found it in, of all places, K-Mart, for $16.95. I checked out the
FAQ on their website as I was worried that with metal particles in the epoxy, it might conduct electricity, but
apparently it's an insulator:


I then applied gentle clamping pressure for a few hours while the epoxy hardened:


Here's a closeup of the busted coil. The part has simply failed, there's nothing putting any pressure on this part in the engine bay, the ignition leads aren't under any tension, there's nothing banging into it, it just simply broke off:


After the first batch of epoxy dried overnight, I then covered all the seams where the black shiny potting compound joined onto the plastic - all around the boots and all around the edge:


Here it is, from another angle:


Then, I covered the sides with a thin layer of epoxy as there were some hairline cracks already developing (I've really got no idea how old this coilpack is) and I didn't want them to get any worse. After this had cured for a few hours, I next covered the whole thing with a thin layer of silicone - reasoning that even if the epoxy cracks slightly, the silicone should be flexible enough to keep it sealed and hopefully help it last longer. I didn't want to put too thick a layer on, as I don't want to provide any additional thermal insulation - I don't want to keep heat in the coilpack, as it is bolted quite literally right onto the side of the engine


Here's a closeup with the silicone showing a pale blue colour, over the grey of the epoxy. I won't be winning any prizes for a neat, smooth finish, but as long as it works...


Here it goes - putting it all back on. I didn't take any photos of taking it off (which was pretty easy) however if you want directions, skip to the end and work backwards, it's an identical process, just in reverse:


Tighten up four hex-head bolts - 5mm from memory:


continued...

[kai_h]

Next, route the control cable through the channel, clip it in and plug it into the coilpack:


When replacing the plastic cover, it will be easier if you undo this wiring loom. It's pretty easy, just unscrew the connector and it easily unplugs:


Put the plastic cover back on. I was able to use a 6mm allen key to do up the bolts on it:


Don't forget this third screw at the rear - also a 6mm allen key sorted me out here:


Next up, replace the ignition leads. All the leads are cut to be just the right length, so is's pretty easy to figure out which one goes where. If you get stuck, the cylinder numbers are marked on the coilpack (hope you can see it through the silicone!) and on my leads at least, the numbers are marked near the end. These aren't OEM leads, I did have to get new ones a while back. I don't think the OEM ones are marked, but they're also all the right lengths, so will easily plug into where they're meant to go.


Here it is, all done and as good as new!


Lastly, to test it I'm running the engine and liberally wetting the area with a trigger bottle. No sparking or arcing, and no rough idle - the engine purrs like a kitten now!


---------- Post added at 04:39 PM ---------- Previous post was at 04:33 PM ----------

This is also a recommended technique to use as preventative maintenance on a VR6's coilpack. It's only needed on the MkIII's as the MkIV engines have individual coil-on-plugs that are far less likely to fail in the first place and a hell of a lot easier and cheaper to replace if they do.

If you've got a MkIII VR6, I'd recommend having a crack at this to possibly prevent future failure

[Stan]

what a great pictorial, well done!

[jono0309]

Fantastic write up. Now gives me the courage to do this myself! Thanks bud.

[kai_h]

Yep, it's pretty easy. Just take your time, let the epoxy and silicone dry completely before refitting it and you're good to go.

[MattyT]

Looks great guy! My coilpack already has some sort of similar goop plastered all over it and I have not had a coil related issue in over 3 years of ownership. Worth it!