Hi all, on removing the ignition coils on my 86 K100 RS project build, I noticed that one is cracked - presumably this coil will need replacing? They seem to be quite expensive, so was wondering if they can be repaired? The affected coil is the forward coil for cylinders 1 & 4. The other coil seems to be fine. Thanks in advance for your feedback 

I'd say that's been dropped. As you're in GB and subject to the same amount of skyp!ss that I am, I'd replace it. The chances are that the sealant around the internal windings is also damaged and once water gets in there (as it will), you'll be stranded in the most inconvenient place possible. Check ebay; if you're in no hurry coils do come up relatively cheaply. I got a pair for £30 after I'd dropped one and smashed the HT terminal off it.

It may have just cracked from age. It's 30 year old plastic that's been exposed to heat and vibration.

That is similar to age related cracks I have seen over the years with those black coils.

I went through a few second hand ones before getting some new red tops. A mechanic told me you can repair them with nail polish.

There is a marine product called "Glove It " that is a slow drying penetrating epoxy that would probably seal that up nicely .   Gloveit Epoxy     If the coil is still in good working order this would fix that crack and seal it up tight.

I would suggest sealing the crack with whatever you like and beginning a search for a set of the later version.  In the years I've been hanging around here I've seen a fair number of those early coils have problems and require replacement.  Personally, I wouldn't trust them anymore.

Point-Seven-five wrote:I would suggest sealing the crack with whatever you like and beginning a search for a set of the later version.  In the years I've been hanging around here I've seen a fair number of those early coils have problems and require replacement.  Personally, I wouldn't trust them anymore.

When did the later version come into production ?

I had thought it was earlier but the parts catalog indicates 9/88.

In response to Yamaguzzi's Post 8
The coils for the 8 valve early K100's are part #: 12131459513. Yes, the original factory installed black only coils are more prone to failure than the later coils with the red towers for the plug leads. If buying from a non-dealer be careful if buying the later "red tower" coils that you are buying the correct type. The visual identifier is that the 8 valve coils have 2 male spade post connectors to attach wiring.
The coils for the later 16 Valve motors also have "red towers" for the 2 plug leads BUT the wiring connector is a rectangular shroud with rounded edges and there are two round pins inside the shroud to attach the wiring. The BMW Part # for these coils is different. 
Be careful to make sure you are looking at the correct coil for your machine before buying. On a number of occasions I have seen them incorrectly identified. 
The excellent guide on our Forum for coil testing is easy to follow. 
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