Hello, I've got a 95 with the 5.0 and E40D. Ever since I bought this bronco I have always had to either change the the cap and rotor or clean them pretty often. When I say often heres what I mean. After only a couple of thousand miles you can start to see build up on the rotor and the points where the rotor passes inside the cap. It seems I am replacing cap and rotor a couple of times a year and I only drive about 12k miles a year. Is it typical for them to corrode so quickly? I live in a dry environment and dont drive through water or mud. I kind of suspect a faulty component in the ignition system somewhere. I have a 66 ford that seems to never have the cap and rotor corrode. This corroding that I refer to is just the typical corroding that you would expect to see after a long time (not like green/moisture corrosion). I think it just happens too often. What do you all think? By the way, I have a new distributor, cap and rotor, MSD coil and new plugs and wires in the vehicle. I have not changed the Ignition control module.

 

Until you find the cause, you can buy some Marine Formula (i don't know if such product exists in the US, but still...) and spray it on the inside on the Distributor, it creates a water resistant film over the parts, so they won't corrode. About that internal moisture, it isn't normal, i've never had any corrosion in neither the cap nor the rotor.

 

I'd bet its the INFREQUENT use that is causing you the issues. Even typically dry climates produce condensation over night EVERY night and if the truck isn't run for a few days the moisture content will corrode things more readily. A good way to determine if this is a potential issue is to have a look at the brake rotors every morning. The flash rust indicates the humidity level the truck endured over night. If its fairly light great but if its fairly light EVERY day then the longer it sits the more likely the problem will extend to other components sitting in the same environment. Brake rotors are bare steel and will show signs of corrosion over night and significant surface rust within days so this is a good indicator as to what the rest of the bare metal components in the truck are experiencing as well. And while brake rotors have the flash rust scraped of physically the first time to stop, other parts don't get this kind of "cleaning".

The cure is simple. Start it/drive it once every couple days and burn any light corrosion off both the brake and ignition rotors. Doesn't even have to be more than around the block.

If this is not the case, poor spark will cause soot to build up because the weaker the spark the less "umph" it has to jump the gap between the rotor and cap. The "cooler" spark produces more soot. However, if this is the case, the spark plugs are suffering the same issue and your performance is suffering for it as well. If the plugs are exhibiting the same kind of deterioration, you might consider replacing a weak ignition coil. and check the connections to it while you are at it. If the primary side of the coil has a weak connection the secondary side will see this problem manifest exponentially.

 

What brand cap? You never did mention that. Over the course of a couple of months I tried out about a half dozen different brand caps, just accumulated over time, came with parts, etc. They all sucked for their own unique reasons..

Any aluminum terminal cap I have showed signs of wear in very little time. My Summit cap with brass terminals doesn't show the same corrosion, but I actually got plastic shavings from the rotor, still the one I ended up using though. My Richport was aluminum, loved it at first but it became sooo flexible when warm that I had to change it out. It sat for a few days off the truck and corroded.

Aluminum shows signs of corrosion pretty quickly when you introduce electricity, it's just how things are. Buy a brass terminal cap if you can't stand seeing the corrosion, though you'll get some green on the terminal ends if you get any condensation it shouldnt affect how it works.

Does anyone make copper or gold terminal caps? I always loved the way copper handled the elements, heck, most of our water pipes are copper. I'm surprised most caps use aluminum.

 

A good quality cap with brass contacts should solve your corrosion problem. You may want to check the side to side play in your distributor rotor shaft. "If" your problem is moisture, you can try spraying the inside of your cap with WD40 and then wipe away the excess.