Distributor discoloration
 

So, I was wondering if anyone could tell me what might be causing the "white stuff" discoloration on the inside of my distributor cap. This AC Delco cap is about six months old.

Thanks!

Bump.

Sorry, I just want to make sure this is normal before I try and return the cap under it's warranty policy.

I am not sure the problem, but please read the forum rules, you must wait 24 hours before bumping your thread if there are no responses.

It is supposed to be there, don't scrape it off. When the cap is installed, silicone dielectric grease is applied to the terminals. The grease retards oxidation on the aluminum terminals. When the engine is running, the current passing through it causes it to crystalize.

Ummm, I don't quite agree. I've yet to see any cap that is pre-coated with dielectric grease on the terminals. Every one I've installed have been bone dry, including the rotor. IMHO, what you are seeing IS oxidation from the aluminum terminals, thus why I only buy all brass caps and rotors.

And I have never seen dielectric grease that has ever crystalized.

YMMV but I'm gonna stick with what I know through out the years.

You're right, none of the caps come pre-coated, it's the responsibility of the tech to apply the dielectric grease. Silver, copper and gold, (in that order) followed by aluminum are the best conductors. Aluminum oxidizes and the spark accelerates it, the grease slows the process. Brass terminals are a sure sign that the manufacturer is cutting costs. Nice selling point cuz they look pretty, but it doesn't perform nearly as well.

I thought he was asking about the white "cloud" like discoloration on the cap, not the grease on the terminals.

wow the whole thing looks a little shotty to me, i always was under the impression that moisture causes the white powedery effect when the ignition fires, and the look of the electrodes inside the cap raises
serious questions. im not a expert but i have replaced caps that looked better than that

Yes, I was referring to the "cloud".

It's an AC Delco cap installed by the local shop. I was just wondering what the cloudy white stuff was on the plastic part of the cap not necessarily the terminals.

Anyway, I ended up wiping off the cloudy residue but let the grease alone.

My guess is there is too much dielectric grease on the terminals causing some to get tossed around as the rotor passes. What is happening is arcing from more than just between the rotor and the individual terminal. Surprised you haven't noticed any misfires due to this.

And yet ANOTHER reason I don't put dielectric grease inside the distributor and use only brass contacts. I've yet to find any out there made of silver, gold or copper. Aluminum oxidizes, brass doesn't. Guess why I go with brass.