why should I change my cap and rotor on the distributor?

[Shawn]

I usually just wait till something breaks before I fix it. Preventive maintance is for people who have money to burn.

 

[Zim Hosein]

Originally posted by: holden j caufield

Originally posted by: SupaDupaCheez
I'll tell you how to figure out if you need a new cap and/or spark plug wires:

1. Take your car to a VERY dark area (inside a closed garage would be fine)
2. Open the hood
3. Start the car (make sure the emergency brake is on or it's in park)
4. Look under the hood (be carefull of the fan.....it is dark you know )
5. If you see sparks coming from the cap and/or wires.....YOU DEFINITELY NEED TO REPLACE THEM (these 'sparks' will probably be a little hard to see)!!!

I asked a mechanic the exact same question when I was 18 (i'm 34) and had a honda with over 100k. He showed me this 'trick' and I was amazed at how much energy was lost due to a cracked rotor or old wires. Lost spark means that your engine is either working harder to burn the fuel or it is just passing the fuel on to your Catalytic converter (either way means a loss of MPG). Needless to say....I now make sure that my wires/cap/rotor are changed at LEAST every other year.

CLIFFS:
1. Just change them

SDC

PS: Make sure you only run the car for a few seconds inside that closed garage...wouldn't want a post from your parents tomorrow accusing us of 'killing you'.

LOL thanks for the tip. I'll give it a try tomm. I just hate taking it to the shop down the road as they always "make up" stuff. I don't mind working on it, as it gives me some pride in my car. But of course I'd much rather not do it all.

holden j caufield, you're "back-peddling" IMO

 

[Insane3D]

Originally posted by: Zenmervolt

Originally posted by: Insane3D
Cap and rotors aren't airtight...and there is no grease on the internal contact points on a new cap and rotor...at least not on the ones I've seen. Condensation...dirt...etc.

Yes, they are. They won't hold pressure, but they absolutely do seal out ambient air. If they didn't, moisture would get in and the car would run like absolute sh!t on any remotely humid day. That's why when the cap cracks it needs to be replaced. There is an o-ring seal at the base and the rubber boots on the wires seal at the terminals. Also, no-one with even half a brain assembles _anything_ electrical without greasing or oiling it to prevent corrosion.

As for the filter, yes I really mean what I'm saying. It's not something I follow on my own cars, but for a "disposable" car it'll still probably run another 100K miles even with a dirty fuel filter. It's not a critical issue.

ZV

No, no they aren't. You can get moisture inside without it affecting things unless there is a lot. I've seen it. They seal out most water, but humid air can still get in there and condense. You've never heard of people needing to let the distributor cap dry out after driving thorugh a puddle, or otherwise getting the motor wet? Condensation from humidity is nowhere near enough to make the car run bad most of the time, and as soon as the engine heats up a bit, it's gone. There is enough however to leave just a little bit of corrosion on the contacts.

Oh, and there is not rubber orings on most distributor caps...there sure is hell is not on mine. As for dielectric grease, it's not the best idea on the underside of the distributor cap IMO. On the spark plugs and wire connections..sure.

I guess my car came stock with a big rubber boot wrapped around the distributor cap for looks?

I guess we'll have to agree to disagree here...I've seen it, and experienced it.

Same goes for the fuel filter...I guess you think you know better than car manufacturers...so, good for you.

 

[bootymac]

Grease monkey fight!

 

[Insane3D]

Whether or not caps are airtight nonwithstanding, the contacts will wear down with time, and the plastic can crack after years of heating and cooling cycles...

The cap and rotor are wear items, which means they do not have an unlimited life span. As the coil feeds current to the spark plugs on distributor ignition vehicles, it must pass through die rotor and cap before it reaches the plug wires. The current arcs as it makes the jump across die rotor gap, which gradually erodes the metal rotor tip and cap electrodes. As more wear accumulates, the gap grows larger and the coil must produce more voltage to compensate. When demand exceeds supply, engine misses and loss of performance may result, which is why the cap and rotor should be inspected (and replaced, if necessaiy) according to die manufacturers PM recommendations.

Perhaps you remember the '70s, when auto manufacturers first touted the "high-energy" ignition systems on their vehicles. Coils in these systems were capable of producing approximately 40kV or more-about twice what the old points ignition systems could put out. This higher voltage capability is now standard on all vehicles. Most of the time, the coil needs to produce only between 10 and 20kV-not much different than in the old days. This is because the actual coil output is always just what's needed to fire the spark plug gaps, no more and no less.

So why is the extra reserve needed? Under normal conditions, the engine will ask the coil for higher-than-normal kV output during heavy acceleration or heavy loading. The engine will also require higher kV if the fuel mixture is either too rich or too lean. A complete lack of fuel really forces the coil to pump out extra-high kV, as it attempts to ignite fuel that isn't there. The extra stress of cranking the engine at cold temperatures when there's no fuel in the cylinder may send an otherwise perfectly good coil to an early grave.

http://www.findarticles.com/p/articles/mi_qa3828/is_200308/ai_n9294719#continue

Distributor cap inspection

At every tune-up visually check the distributor cap and rotor for damage, burns or corrosion. Check the spark plug towers and their terminals under the cap to be sure they are free of corrosion that would inhibit proper spark distribution. Replace any damaged or worn components. One often overlooked part of the distributor cap inspection are the terminals on the underside. Small burn spots or deposits of corrosion here can lead to engine misfiring.

Inspect the rotor for cracks, excessive burning of the contacts and mechanical damage, and replace as necessary. Slightly burned contacts should be sanded smooth.

While primary wiring is less perishable than the secondary circuit, it should be checked for cracked insulation or loose connections. Tighten connections or replace wires as necessary.

If the spark plug wires have become unserviceable due to time and wear, it is probably a good idea to replace the cap and rotor as well..[/b]

http://www.procarcare.com/icarumba/reso...resourcecenter_encyclopedia_tuneup.asp

Originally posted by: bootymac
Grease monkey fight!

Nah, I doubt I'm going to change his mind, and vice versa. I've experienced what I'm describing, so I'm not concerned about proving it. So, sorry...no fight.

 

[Zenmervolt]

Originally posted by: Insane3D
You've never heard of people needing to let the distributor cap dry out after driving thorugh a puddle, or otherwise getting the motor wet?

What part of "it won't hold pressure but it will keep out ambient air" didn't you understand? Yes, if you pressure wash your engine or even use a hose on it you can breech that seal, but a cap in good condition will not let ambient moisture from outside air enter the distributor.

Originally posted by: Insane3D
Condensation from humidity is nowhere near enough to make the car run bad most of the time, and as soon as the engine heats up a bit, it's gone. There is enough however to leave just a little bit of corrosion on the contacts.

Funny, when my distributor cap cracked (and on every other cracked distributor cap or cap with a failed o-ring at the base, etc) the first notice came on humid days because the car ran like crap for 15-20 minutes. This happened long before any carbon tracking occurred or other potential reasons for the mis-fire existed.

Originally posted by: Insane3D
I guess my car came stock with a big rubber boot wrapped around the distributor cap for looks?

So since your one car had an alternative method for sealing off the distributor all other cars must need one too?

Originally posted by: Insane3D
I guess we'll have to agree to disagree here...I've seen it, and experienced it.

Same goes for the fuel filter...I guess you think you know better than car manufacturers...so, good for you.

Again, what part of "I wouldn't follow this advice with my own car, but on a disposable vehicle it's not critical for operation or safety" didn't you understand?

It's not good, but it's about as far from a critical repair as you can get on a 180,000 mile junker.

First rule of being a mechanic is to know what the customer is looking for. If the car's old, the owner is cheap, and he's just driving it until it dies completely there's no point in suggesting maintenance that's not a safety or immediate functional issue.

ZV

 

[ironcrotch]

Oh god just change the damn thing. It's like 40 bucks and takes 10 minutes. Crap.

 

[jlee]

Originally posted by: ironcrotch
Oh god just change the damn thing. It's like 40 bucks and takes 10 minutes. Crap.

40 bucks? You must buy fancy stuff.

I think I paid about 3 bucks for a rotor, and $20 or less for a cap..

 

[91TTZ]

Originally posted by: holden j caufield

Einstein, I said I haven't changed it in 100k. Got changed at 80k before. Nice that I've got some loser keeping track of my mileage.

No you didn't. You said "after about 100,000 miles I haven't changed it". This could have multiple meanings since it's vague. Sadly your grammar is about as thorough as your car maintenance.

 

[cjgallen]

Originally posted by: CadetLee

Originally posted by: ironcrotch
Oh god just change the damn thing. It's like 40 bucks and takes 10 minutes. Crap.

40 bucks? You must buy fancy stuff.

I think I paid about 3 bucks for a rotor, and $20 or less for a cap..

It was K&N

 

[glenn beck]

cheaper than changing the distributor itself but hey not my car

 

[aircooled]

Originally posted by: holden j caufieldwhy should I change my cap and rotor on the distributor?

To make your old car more reliable and last longer.

 

[Insane3D]

Originally posted by: Zenmervolt

Blah, Blah, Blah...

ZV

Ok, whatever you say.

 

[nakedfrog]

I'd at least buy the parts and keep them in the car just in case. But then you might as well change them, it's not a lot of work or anything.