Do Coils Leak?

[Bingster]

Is there anything in a 6v coil that could cause an oil-like film at the bottom?  What is the service life of a coil?

[Los_Control]

does automotive coil have oil

 

There's oil inside many round ignition coils, used as an insulator. If the coil is overheated, the case can rupture, allowing the insulating oil to leak out. That then allows to coil to overheat faster next time until it separates an electrical winding and stops providing a spark.

 

Thats just from a quick google search & first hit.

I remember in decades ago hearing about them leaking but was not sure. ..... Seems modern coils do not?

[TodFitch]

1 hour ago, Bingster said:

Is there anything in a 6v coil that could cause an oil-like film at the bottom?  What is the service life of a coil?

Second question first: The service life is indefinite. The coil in my 90 year old Plymouth is, near as I can tell, also 90 years old and working fine.

 

First question: Yes. There is an oil or wax material in the coil and if it is leaking you have a bad coil or one that will be bad shortly.

 

Here is a bit of a long story. . .

 

Way back in the 1970s my daily driver was an oval window '57 VW Beetle. I purchased it in the winter and occasionally on long drives it would act like it ran out of gas. I'd remove the air cleaner and work the throttle and see gas spurting in the throat of the carburetor from the accelerator pump. Got gas. I'd pull a spark plug wire, lay it near some metal on the engine and bump the starter motor and I'd see a spark. Got spark. Hmmm. With spark and gas it ought to run. I'd poke and prod things around the engine compartment looking for loose hoses or wires and find none. Then I'd try starting it and it would fire right up and I'd drive off.

 

As the weather warmed up this roadside ritual became more and more common. I got pretty fast and running through the checks and never found a "smoking gun" and the car would fire right up after the ritual was performed. Finally, on a warm day in June while coming home from work it happened again. This time while cleaning my hands after performing the ritual, I noticed wax on my hand. I had no idea where I could have gotten wax on my hands from inside the engine compartment so I started looking very closely at everything I had touched to see where it had come from. I found a small crack on the tower of the coil with wax seeping out. I picked up a new 6v coil at the local auto supply and never had that mysterious "it seemed to run out of gas" failure again.

 

In retrospect, I think if I had checked the spark before I checked for fuel I might have found the problem earlier. But it always felt like it was running out of gas so I always checked the fuel system first which gave the coil some time to cool down before I checked for spark.

 

A bit shorter story. . .

 

A number of years back we had a multiple day tour from the SF Bay Area to Tucson for a Plymouth Club meet. One car on the tour, a P15, was having issues climbing hills. From outward appearances and from the driver’s description it seemed like a fuel delivery issue. Turns out it was a weak coil. Once I found that out I did some research and found that the more pressure there is in the cylinders the more voltage it takes to initiate a spark. With a weak coil the car would start and run fine unless or until you needed full power. With the throttle wide open you get more fuel/air mixture into the cylinders which means a higher pressure on the compression stroke which needs a hotter spark to ignite. So the engine would lose power on the steeper uphill grades and it felt to the driver just like it wasn’t getting enough gas.

[Jerry Roberts]

I had two old coils sitting on the garage shelf for years . They both started leaking oil so I threw them out . 

[Tom Skinner]

If they leak, I would replace them as a Parts House guy I know said they usually only last 7-8 years nowadays anyhow.

I would think yours is on its way out, In addition to that FYI they are (6 Volts) about $21 at O'reilly's, or NAPA.

But I am sure some of the older ones lasted seemingly forever as my first 1948 Chrysler (owned from 1973-1984) never needed one

and in addition to that looked original (making it 36 years old at the time of selling my car and still going).

I don't like telling people advice but a symptom of a coil on its way out is the car may start and run, but once warmed up on the road say 15 minutes it may stall out.

Once it cools off again it will start the car again, my experience with the 1948 Chrysler I now own (2007-2023 at present).

It took me quite a bit of replacing Ignition Parts to figure out my coil was indeed leaking and once I replaced it I have had no more stalling issues.

Good Luck with whichever course of action you decide to take.

Tom Skinner

Huntersville NC

Edited September 28, 2023 by Tom Skinner

[Bingster]

Thanks for all the info. Yeah, to the parts store I go.

[Marcel Backs]

Go for an Echlin or MOPAR $$$ if you can. The NOS ones if properly stored in my opinion are superior to the off shore material which is junk. and floods the market. For NOS parts like this try Minakers Auto Parts or Pre Sixties Vintage Auto Supply in Ontario. Both have websites and lots of NOS parts in impressively well preserved  condition.

[rallyace]

I have found 6 volt coils at both Tractor Supply and Runnings. Those old gas tractors had 6 volt systems and a lot of them are out there still working as hard as the day they were new.

[Bingster]

Rock Auto has them as well as Napa and I was going to order one from Rock Auto cause it was cheaper but when you added Rock Auto shipping it was the same price as Napa.  Maybe Rock Auto is a better quality.