Coil oil fill-up

[Melchior]

I have the red Magneti Marelli 12V BZR 201A coils in my 250 GTE and one of these seems to miss oil. I want to fill-up and have two questions: a) which oil shall I use and b) to what level shall I fill-up?

I read that these coils might have been filled with PCB which due to its toxic attitude is not available anymore. Any comments to that?

I guess that the oil needs 10-20% space to extend when it gets hot, so I assume that this should define the oil level when cold?

[John Vardanian]

Mineral oils are non-PCB and are used nowadays in utility transformers. The vintage automotive coils operate in a similar high voltage environment as the utility transformers. The paper inside both is really the insulator. Paper alone is an okay insulator, but once it becomes impregnated with oil it becomes an exceptional insulator. Remember that paper has a wicking quality, so you need enough oil to keep the paper wet even when the coil is fixed on its side. I would say that in manufacturing, oil is filled up to below the rim of the metal can in one operation before the plastic head is pressed onto the can in the next operation.

https://www.youtube.com/watch?v=ewHkek5_pSk

john

[Melchior]

Hello John, thank you for this information. I only thought about the heat transfer, but you are right of course,the lifespan of the paper is affected by the oil. I have organized mineral transformer oil Nytro T 4000X. The question is if the mixing with the old oil inside of the coil will have any negative effects? I am also uncertain so far if I shall empty the coil before the refill to have as little of the original oil in there as possible or just fill up. Any thoughts about this?

[John Vardanian]

After the EPA mandate, the large scale utility transformers were simply drained, flushed and refilled with mineral oils. There is no compatibility concern, like you might have when converting from DOT4 to DOT5 brake fluid.

john

[Melchior]

Thank you very much!