Engine Coils-Prophylactic Replacement??

[tom slick]

prophylactic means to "prevent disease" in any context.

 

[JOD]

Originally Posted By: tom slick
Unless these coils have a history of failing, the chances of having a defective coil are just as great as one of your current coils failing. New components don't equal higher reliability.


Well, that's why I was trying to get an idea of the failure mode. I was having a hard time figuring how copper windings with relatively low voltage going throw them would just 'go bad'.

I was able to x-reference the coils on the Freestyle; seems they're used in a couple of other Ford vehicles, so I checked out some car-specific forums to check on the failure mode and frequency. Bottom line is that these coils don't seem to be particularly problematic, and most of the failures are either due to worn/cracked boots or fouled plugs.

I've decided I'm going to replace the boots and springs (a few different folks recommended the Borg and Warner or NAPA boots) with each plug change, clean up the coils with some electric cleaner, put on some dialectic grease on the coil/boot and re-install the old coils. If a rear fails, I'm sure removing the UI manifold will be a lot easier the second time around. This makes a plug change a $50.00-$100.00 deal (depending on which plugs) versus >$500.00, which seems a little nutty to me. There were a few people who reported long life out of these coils (>300K miles) going this route, so hopefully I'll be as lucky.

If I remember, maybe I'll resurrect this post from the dead a few years from now after my next plug change!

 

[George7941]

Originally Posted By: JODmode
I was having a hard time figuring how copper windings with relatively low voltage going throw them would just 'go bad'.



You omitted two facts. Only the primary side has low voltage, the secondary windings carry 10kv plus. Even on the primary side, the voltage shoots up to over 300v at the point of current interruption because of back emf.

Secondly, even if the voltage is low, the current is relatively high, at 4 to 5 amps, and this leads to heat generation in the windings.

 

[JOD]

Originally Posted By: George7941

You omitted two facts. Only the primary side has low voltage, the secondary windings carry 10kv plus. Even on the primary side, the voltage shoots up to over 300v at the point of current interruption because of back emf.

Secondly, even if the voltage is low, the current is relatively high, at 4 to 5 amps, and this leads to heat generation in the windings.


Well, that's why I said 'relatively' low voltage--I probably should have been a little more clear.

I was figuring (though I don't know this for a fact, which is why I was asking the question!) that even those voltages and currents were low relative to the capacity of the coil. While there will be some degradation of resistance in the coil over time, it would seem that unless there was a catastrophic event the coil windings should last the life of the car.

As I said though, I certainly don't know this, which is why I was asking in the first place. Do you think the degradation in resistance of the coil over time is significant enough that it would merit replacement at a specified interval?

 

[Carbon]

I tend to like dielectric grease around automotive high voltage areas. I suggest you search for references to that. The thing you want to avoid is arcing over insulators that might get a conductive film on them.

Otherwise, I would not replace coils that were not associated with codes in the computer. But I am no expert on that.