When do you really need new spark plugs

carnut13

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I see a lot of spark plug changing going on on the Forum but Id like to know when do you really need to do this rather expensive job?

My service book says 50k miles for a V6 R230....whats the danger of exceeding this mileage?. Why not wait till I get a misfire or will it impact on another part of the car, eg Engine management unit etc
 

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It is said that you should not leave them much longer due to them being difficult to take out, but another 10k cannot make much difference.

This is something that you can do at home a few at a time
 
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carnut13

carnut13

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It is said that you should not leave them much longer due to them being difficult to take out, but another 10k cannot make much difference.

This is something that you can do at home a few at a time

Thanks

So its a time thing. MB recommend 4 years so at 6yrs Im pushing it. Will get it done.
 

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Thanks

So its a time thing. MB recommend 4 years so at 6yrs Im pushing it. Will get it done.

Ollie has said Steve that they can be pigs to get out sometimes, I am at 36k now so I must start thinking about it before now, though I could just remove them and put them back in again, if there is nothing wrong with them.

I think the same as you:D
 

GCLTuning

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would not leave them to long you will have problems if they become stuck in the head !

Let alone decrease in performance economy & CO2 due to un-burnt fuel . You relay need a nice clean healthy spark ....

Regards
 

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As mine are 7 years old I will see how easy one comes out
 

LYNALL

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Did wifes a couple of weeks ago and they were very easy 2001 c320 75k not original plugs, also did mine last year and were much harder to get out 2001 e430 105k not original plugs, everything was just that little bit tighter and made you wonder as you cracked them off!.

Lot of yank sites reckon 100k for the plugs.



Lynall
 

MBDevotee

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Dreaming of a CL55k - one day maybe....
But why would you want to leave them longer???

One of the most important things for a decent running engine is a good spark, and I don't think you can grumble at plugs lasting 40K !!!!

I would probably change them more often not less if it was me!
 

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But why would you want to leave them longer???

One of the most important things for a decent running engine is a good spark, and I don't think you can grumble at plugs lasting 40K !!!!

I would probably change them more often not less if it was me!

You have not got 16 of them to change ;):D
 

turbopete

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i found a number of tricks for removing spark plugs/making next removal easier over the years i worked in garages. the 1st obviously is to het the engine hot if theyre tight, particularly if they have a tapered seat rather than a washer on them. 2nd, look up the correct torque setting and tighten them to that, an easy rule of thum if you havent a small torque wrench for low torque is to screw them in, using socket extension if necessary, as far as possible by hand only. you can tell when you put your ratchet or bar etc on if theyre down to their seats. then give them a max extra turn of 90degrees (1/4 turn). this is tight enough as most cars have a torque setting of around 18-25nm for the plugs. 3rd only pplies to taper seat plugs, but i will mention it anyways. a very thim smear of copperslip onthe TAPER ONLY prevents the plug and the seat 'corroding' together. finally 4th is to simply undo them slightly then re tighten every service or so. hope thats of some help to someone!and
 
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grayb

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I was told (by someone who didn't have an axe to grind) that leaving the sparkplugs can result in Cat failure, as combustion doesn't complete properly and unburnt fuel contaminates the catalysers. He said that he wouldn't take a chance if it were his car.
 

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I was told (by someone who didn't have an axe to grind) that leaving the sparkplugs can result in Cat failure, as combustion doesn't complete properly and unburnt fuel contaminates the catalysers. He said that he wouldn't take a chance if it were his car.

It does not really work like that as our cars have an O2 sensor that detects any burning issues with the fuel
 

Number_Cruncher

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>>It does not really work like that as our cars have an O2 sensor that detects any burning issues with the fuel

I wouldn't be quite so sure - misfires and partial burns have to be quite bad before they get picked up via the oxygen or lambda sensor.

Oddly, a complete misfire will result in there being lots of oxygen in the exhaust, which the lambda sensor will interpret as a weak mixture, and will richen accordingly!

The ECU detects misfires not via the lambda sensor, but, via measuring the angular acceleration of the crank after every firing event. If the crank doesn't change its rotation in the way the ECU expects it to,... ping!, the engine management lamp comes on.
 

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But to get to that stage the car would be missing badly, and this is something that the cars in this thread do not do, they drive perfectly, even when way past the change date, these plugs do not age, and many are under the required mileage, and the time thing has come into play
 

Number_Cruncher

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Another way to phrase it is that by the time a misfire is obvious to the driver, you've already washed a heck of a lot of unburned fuel down through the cat!
 

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Another way to phrase it is that by the time a misfire is obvious to the driver, you've already washed a heck of a lot of unburned fuel down through the cat!

I think that is to over the top,, plugs are good for 60k so it is said, 70k will not change thing by much if anything at all
 

Number_Cruncher

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>>I think that is to over the top

Perhaps we're at crossed purposes Malcolm.

All I'm saying is that leaving it until the engine management light comes on is too late.

My default position in the absence of trustworthy data to the contrary would be simply to change them with new plugs from MB at the specified interval using the speified procedure - nothing more, nothing less.
 

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My last word is that we have never had a plug fault that has turned on the lamp as of yet
 

louwdj

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Some cars / manuals says for alluminium heads, engine must be cold when unscrewing and fitting spark plugs. Any opinions?

On E240 V6 (112 engine) platinum type x 12: ~UKP90 to change. Will not do until 100,000kms, unless absolutely necessary.
 

Number_Cruncher

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>>My last word

I think this is one of those instances where the internet has got in the way of communication. If I've said something that's wound you up, then, sorry, that really wasn't my intention.

>> is that we have never had a plug fault that has turned on the lamp as of yet

Yes!!, we are in broad agreement. By the time the light is on, the misfire has been there for a long time already, waiting for the engine management light to come on is a very poor way to judge when you need to change the plugs.

The O2 sensor cannot and does not correct for misfires though.
 


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