ignition coil cutting out due to overheating

[Hans Efde]

I can understand a coil failing totally through overheating, but not why it should recover when it cools down. After all. it's only two coils of wire.

Me neither, but I won't complain. It saved me a 4 mile push home. It seems to be common for coils to recover having googled this type of failure. Only the ones that exploded obviously were terminal.

[mikeeskriett]

I suspect it's to do with the insulation and the oil inside aldon list a few types oil, and epoxy filled also I suspect they may have some form of thermal protection similar to that found in transformers. The exploding ones just get hotter until the oil expands and blows the end off with a nice smelly mess.

I'd measure the voltage from the +ve to earth should be 13.3 with both coils fitted. Your voltage differences bay be due to the electronic ignition and the way tthe coils respond to the trigger, on my car I don't actually get much of a reading across the coil.

[Hans Efde]

Today I had another testdrive of around 10 miles. Most of it around and through town and a few stretches of road where I could let the car run at 100kph. No ignition problems. At return I did a few temp readings (degr. Celsius):
coil: 55
head: 76
exhaust manifold at cyl. no. : 119
turbo housing: 195
So the coils stays at an acceptable heat level and the car is ready for the MOT. After that the engine will come out and become turboless. I was amazed how hot the turbo becomes after such a short stretch of road compared to the exhaust manifold. I will miss the power though. Darn it's fast!

[mikeeskriett]

A good result there!

Good luck for the MOT, mine is down for a test in the next couple of days it had better pass!!!