Replacing only distributor rotor but not cap

[PandaBear]

When I replace both last time, I noticed that the cap terminals have residues but the rotor has white powered coating on top. Since most plugs that I have replaced seems to have worn tip rather than ground, can I assume that cap/rotor wear the same? that sanding off the terminals on the cap and put new rotor on will be sufficient?

The application is 95 Corolla, and the cap/rotor has been used for about 60k miles.

 

[Dave Hess]

If it was my car, I would replace both since it has 60K miles.

I noticed on Hondas, the cap & rotor gets dogged within 40K miles.

 

[another Todd]

Your good since you replaced both last time. Your rotor takes an arc four times (on a 4 cyl) for every single arc of each terminal of the cap, so it does wear faster.

 

[PandaBear]

How does a cap/rotor wear? Is it oxidation or is it lost of material due to arcing? Will sanding off the oxidation help?

 

[punisher]

Depends. There is a very high concentration of ozone internal to the cap. Oxone is reactive. Many manufacturers put a coating on the end of the rotor and the internal cap terminals to resist corroding due to the arc and the accompanying ozone. If the original cap/rotor was uncoated, don't worry about it. If it was originally coated there is a small chance wear will accelerate after cleaning. A cap terminal or rotor doesn'r have to be shiny to conduct well.

 

[PandaBear]

So, how do you know when to replace it? By the miles? By resistance? By Gap? or by look?

I cleaned up the cap and rotor about 2k miles ago with 800 grit sandpaper, and the engine ran smoother for about 2k, then now it is back to original, and I started seeing a lot more deposits on the cap terminals and the rotor terminals look darker/oxidized.

The new rotor has a white coating that the old one does not have (or maybe it is already worn and is now grey/black looking, with coast texture). Some people said replace it every 30k, is it true?

 

[MC5W20]

A '95 with a cap and rotor. Geez what archaic technology for that year vehicle.

 

[Tosh]

Short on money or for discussion's sake?

I would feel pretty pleased if I got 60k from a cap and rotor, and would replace both with the same brand as those. (OEM, presumably?)

 

[mechtech2]

The observation about 4 to 1 wear is very valid.

 

[PandaBear]

Quote:

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Short on money or for discussion's sake?

I would feel pretty pleased if I got 60k from a cap and rotor, and would replace both with the same brand as those. (OEM, presumably?)

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Both. I am $600 short of each month's mortgage until my bonus come out this year. Just got an unexpected expense (wedding related). Since I am doing everything myself and can replace the cap/rotor during lunch time in the parking lot, I feel that it is better to "save the environment" and a few bucks along the way if I can.

Already sanded once, so maybe not a good idea to keep sanding every month.

 

[tom slick]

if the engine is running ok and the rotor's tip isn't erroded then just sand off the oxidation and keep on going.
replace it when you have a few extra bucks. the numbers for replacing wear items are arbitrary anyway.

 

[John_K]

Interesting, I replaced my cap and rotor after 75k miles and both looked brand new.

John

 

[Doc8404]

the Mazda and Mitsubishi need to be changed every 6-12 months like clockwork.