Of Distributor Caps & Dielectric Grease

Phipi's "watch conundrum" thread reminded me of an old personal mystery. tonyp12 mentioned dielectric grease around the battery terminals as a potential problem...

I was a grease monkey (Ford dealership mechanic) in the summer of 1980, when I bought my trusty(?) Corvair. Then-modern cars had electronic ignitions with distributor caps & rotors. Any time we did tune-ups or ignition system repair, we followed dealership SOP and sprayed a bunch of ordinary aerosol lithium grease inside the distributor cap. Indiscriminately, everywhere. I asked everyone there why (izzit supposed to conduct or insulate or seal?) and never got the same answer twice. I never did this on my own car with old-school points & condenser, quite the opposite, I kept it real clean.

My best guess is that on the electronic ignition cars, the HV spark mostly burns/vaporizes the grease away, and whatever bit is left runs down to make a pseudo-seal around the distributor cap to keep dirt & water out.

The debate rages on at https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=552408

Anybody have more insight?
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

- Pablo Picasso

Comments

  • 24 Comments sorted by Date Added Votes
  • I have never seen anyone spray the inside of a cap before, and there is some loose nuts in that fourm.

    I was a Kawasaki motorcycle & jet ski, Seadoo and other brands of watercraft mechanic, so no distributor
    caps.

    Perhaps they thought it would make it water proof? VW's seem to quit, right after they drive through a
    mud puddle.


    Bill M.
  • When I had my Pinto wagon (four used cars ago), the last thing I would ever have wanted under the disty cap was any kind of lubricant. The screw that held the dwell plate in place was always coming loose as it was. As a consequence, I always carried a dwell meter/timing light to fix it when the car stalled -- as it did one rainy Friday evening on the Mercer Island bridge during rush hour. Fortunately the responding cop was kind enough to hold a flashlight in the rain as I readjusted the dwell and timing. Man, I hated that car!

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • When I had my Pinto wagon (four used cars ago), the last thing I would ever have wanted under the disty cap was any kind of lubricant. The screw that held the dwell plate in place was always coming loose as it was. As a consequence, I always carried a dwell meter/timing light to fix it when the car stalled -- as it did one rainy Friday evening on the Mercer Island bridge during rush hour. Fortunately the responding cop was kind enough to hold a flashlight in the rain as I readjusted the dwell and timing. Man, I hated that car!

    -Phil

    If I recollect, it had a proper funeral. :)

    Can't find the picture right now.


    Infernal Machine
  • Publison wrote:
    If I recollect, it had a proper funeral.

    Proper execution. Didn't deserve a funeral. :)

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • 'Guess I'm lucky to be alive! I was rear-ended in Calgary once. Rather than pay the insurance deductible, I replaced the dented rear bumper with one made of 2x4s. (You can see it in the photo that Publison posted.)

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • What's your life worth? Pretty creepy to hear Ford calculate.


    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Back to the original question, I have used dielectric grease on all points on the distributor spark plug cables and battery terminals. I have found they may hold up better than not applying , but I do not have any scientific data to support that. They just seem to last longer.
    Infernal Machine
  • Publison wrote: »

    Ah, the unforgettable Pinto. I drove one for about a year after returning my company car when five of us started our own service business. Always wondered if today was the day my seat would drop through the floor going over the dipsy-doodle on the way to downtown Toronto. Must have been 8-10 inches of flex up and down.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Publison wrote: »
    Back to the original question, I have used dielectric grease on all points on the distributor spark plug cables and battery terminals. I have found they may hold up better than not applying , but I do not have any scientific data to support that. They just seem to last longer.

    Never heard of anyone using grease on the distributor cap innards, but I think it would be wiped off as the rotor passed over the contacts.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • See this for some info.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • I have heard of spraying the inside of the cap with WD-40. But that's to drive out moisture, which can lead to arcing.

    My next three cars, including the current one, were fuel-injected diesels. I do not miss dwell and timing adjustments, cracked disty caps, or spark plug cleaning/gapping/replacements one little bit.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • Erco,

    Was spraying a distributor cap with silicon spray a procedure or did someone tell you to do that?
    For my late 80's Escort I remember the Ford manual said to apply dielectric grease to parts of the rotor and I believe also the plastic just outside the points of the cap. It also said to apply dielectric grease to the inside of the spark plug boots.
    Dielectric grease is support to prevent arcing and I think I saw it on the light bulb terminals of a Toyota.

    One thing that drove me batty was that I had to keep replacing the spark plug wires of my Escort because after the 2nd or 3rd time one of the wires would no longer lock on the spark plug. Even Motorcraft wires did that.

    I've only had to replace my Toyota plug wires once.
  • If Ford Maverick owners can't sort it out, what chance do the rest of us have?

    http://mmb.maverick.to/threads/dizzy-dielectric-grease.79919/
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Genetix wrote: »
    Erco, was spraying a distributor cap with silicon spray a procedure or did someone tell you to do that?

    Never saw a TSB, but my boss did it and told us all to do it. He had the fastest Mustang in the Lowcountry and I was a punk kid who could barely afford a $650 Corvair, so who was I to argue? :)

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • ctwardellctwardell Posts: 1,634
    edited September 29 Vote Up0Vote Down
    I have heard of spraying the inside of the cap with WD-40. But that's to drive out moisture, which can lead to arcing.

    My next three cars, including the current one, were fuel-injected diesels. I do not miss dwell and timing adjustments, cracked disty caps, or spark plug cleaning/gapping/replacements one little bit.

    -Phil

    Drove my '78 Z-28 through about a foot of water, engine died, still no go after about 12 hours. My father shows up with a can of WD-40, thoroughly sprays inside of the HEI cap, starts right up.

    C.W.

  • My dads old Triumph Dolomite started misfiring one day. On checking the sparks one cylinder looked deprived of any zap. When I opened up the distributor I found a curious thing. A long thin hair line of carbon deposit had formed inside the distributor cap from the HT lead coming in at the top to one of the outputs on the circumference. I scratched it away and cleaned it up with WD 40 and the car was purring again.

    Perhaps some dielectric grease in there might have prevented that.

    We just put it down to the usual crappy Lucas electrics.

    Old Minis did not like the wet. What with having their spark plus in a line facing the front grill. Drive through a big puddle and you are stuck. They could have used a gob of dielectric grease as well.

  • kwinn wrote: »
    Publison wrote: »
    Back to the original question, I have used dielectric grease on all points on the distributor spark plug cables and battery terminals. I have found they may hold up better than not applying , but I do not have any scientific data to support that. They just seem to last longer.

    Never heard of anyone using grease on the distributor cap innards, but I think it would be wiped off as the rotor passed over the contacts.

    I use it on the outside only. Plug and Coil wires.

    Infernal Machine
  • Publison wrote: »
    kwinn wrote: »
    Publison wrote: »
    Back to the original question, I have used dielectric grease on all points on the distributor spark plug cables and battery terminals. I have found they may hold up better than not applying , but I do not have any scientific data to support that. They just seem to last longer.

    Never heard of anyone using grease on the distributor cap innards, but I think it would be wiped off as the rotor passed over the contacts.

    I use it on the outside only. Plug and Coil wires.

    Outside on plugs, coil, and wires makes sense. Keeps water, oil, and crud from damaging the plastic and rubber components. Used silicone grease on my cars for that.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Erco,

    Standards were a lot laxer back then but I will ask my fast Mustang friend about that.


    Kwinn,

    I still have a tube of tune-up (dielectric) grease that I bought back in the mid 90's. I use that and anti-"sleeze" when I change plugs.
  • Heater. wrote: »
    My dads old Triumph Dolomite started misfiring one day. On checking the sparks one cylinder looked deprived of any zap. When I opened up the distributor I found a curious thing. A long thin hair line of carbon deposit had formed inside the distributor cap from the HT lead coming in at the top to one of the outputs on the circumference. I scratched it away and cleaned it up with WD 40 and the car was purring again.

    Perhaps some dielectric grease in there might have prevented that.

    We just put it down to the usual crappy Lucas electrics.

    Old Minis did not like the wet. What with having their spark plus in a line facing the front grill. Drive through a big puddle and you are stuck. They could have used a gob of dielectric grease as well.

    Triumph Dolomites? That takes me back (though the Toledo was the real classic)!

    As any fule no, the risk of wet distributors can be mitigated with a rubber glove with one spark plug lead out of each 'finger' and the HT lead through the thumb.
    South Saxons - "we wunt be druv".
  • Ford Pinto I remember it well. I've built thousands of those at a rate of one per minute at the factory. The fix for the gas tank was the spare tire. So now the position was bumper, spare tire, and then the gas tank.
  • Erco,

    I talked to my Mustang friend and he doesn't like to use anything on the distributor cap.
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