Cracked Coils
 

How common are hairline cracks in the coil packs?
Is presence of any tiny cracks grounds for replacement?
What is the common wisdom on this topic?

TIA

Hairline cracks are the shape of things to come.
If you live in a dry climate, the coils may last for many thousands of miles - if you live in a wet, salty enviroment, they may only last ????
The cracks you see are the visual breakdown of the coil insulation - resin composite - and without an insulation resistance tester its difficult to diagnose the depth of the faults.
If in doubt, replace - they are not expensive items compared to HT voltage (spark) breakdowns and CEL problems....

Yeah. How common was that kind of hairline? Tell us more about it.

Cracks in the coil packs do happen but are not something that I'd consider to be common. I'd replace any coil pack that had a crack, even hairline, because its an opportunity for the coil pack to lose voltage and its probably not going to get better on its own.

Depending upon the age and usage of the car, cracked coils are not at all unusual or uncommon. but as someone mentioned earlier, if you find one with a crack, replace it; it ain't going to heal, and it is going to get worse.............

Holy crap !!!! " Porscheisabella" Tell us more !!!

I am impressed... Are you a Detective or Private Investigator??

Neither, just drag and drop a picture onto google images and it will find like images for you. You get a lot of info that way.

I replaced all six on a 2003. I notice 2 last winter @ 35K all the rest showed some cracking this year 42K.

Here is what happens if you leave those hairline cracks get worse.
http://986forum.com/forums/uploads01...1331092793.jpg
http://986forum.com/forums/uploads01...1331092818.jpghttp://986forum.com/forums/uploads01...1331092860.jpghttp://986forum.com/forums/uploads01...1331092965.jpg

That was the worst one that i pulled out of my car. The others had small hairline cracks so better replace them all. Just so you know the car will run but it is guaranteed that it wont be at its full potential. Also it is definitely cased by snow and salt, so people in warmer weather wont have to deal with this as often, but cold weather and rain can also be a factor. Another note is that the driver side coils were worse then the passenger and the ones that were more exposed to the floor and wheel are the ones that have it worse.

I'm pretty sure the magic number is like 30k miles. After that, all bets are off on the coils. My TT has 45k miles and runs fine, but I ordered a set of coils to have on stand by. If anyone is interested, I found them for $250.00 shipped and they're the updated part number too.

Is coil life dependent on plug gap? My Saab had individual coils in a cassette which had a tendency to crap out and leave you stranded. If you religiously kept the plug gap within spec, the coils would last forever. Apparently, as the plug wears, the gap gets bigger and more current is needed to get across the gap. More current stresses the coils, leading to failure.

Wonder if thats whats going on with Boxsters.

Plug gap can certainly affect coil life...... A coil is basically a transformer - low voltage in (LV), high voltage (HV) out.

If your perfect plug gap is +/- 1.5 mm, the HV will jump the air gap easily causing a nice fat juicy spark.
If you were to set the air gap to double, say 2.0 mm, the HV would have difficulty jumping that size air gap and the spark would be intermittant, causing a misfire, especially when the engine is under load.
Increasing the gap to an even bigger gap of 3.0 mm, the HV cannot jump the distance at all and the coil cannot discharge its voltage which can lead to the coil overheating and eventual breakdown.

Adding coil cracks (full of moisture) to the recipe will cause tracking across the insulator reducing the HV which automatically reduces the strength of the spark - hence intermittant misfires.

One of the advantages of the Porsche specified Beru / Bosch sparkplugs is that they have 4 (sometimes 2) earthing electrodes which helps maintain the set gap to the HV centre electrode.
Of course, if you wear out the centre electrode by running the plugs beyond the recommended intervals, the air gap will increase, but you would (should) have misfires before the coil actually fails.....