C55 AMG - spark plugs

[aquanaut]

Hello, own a 5 1/2 year old C55 with 39k on the clock. It's going in for a service next week and was wondering if it would be advisable to change the spark plugs. Not experiencing any issues. Advice appreciated.
Thanks

 

[BlackC55]

They are due every 50k or 4 years. There are 16 plugs and at a dealer its going to be around the £300 mark.

 

[C240Sport97]

They are due every 50k or 4 years. There are 16 plugs and at a dealer its going to be around the £300 mark.

I don't understand why spark plugs need to replaced on a time basis. If they have only done, say 18k miles in 5 years, why would they need changing, they haven't "sparked" that many times compared to 50k miles.

 

[kwakdonut]

They can still deteriorate though and TBH I wouldn't really want to leave plugs in too long as have had issues in the past with them being 'seized' in!

 

[BlackC55]

Exactly. They seize in. Steel plug in aluminuim head......

 

[DRBC43AMG]

I am thinking of changing my plugs in my 99' C43 at the same time as I install Magnecor KV85 ignition leads (ordered from the factory in the UK). I am considering a set of 16 Iridiums (NGK IFR5D10) to upgrade and ensure a nice smooth running engine. To avoid problems with possible thread seizure, should I envisage "greasing" the plug threads? If so with what type of lubricant?
P.S. I also have a 98' C240T with a M112 V6 and I discovered that it has the same type plugs as in the M113 engine V8.

 

[mr. shr]

I am thinking of changing my plugs in my 99' C43 at the same time as I install Magnecor KV85 ignition leads (ordered from the factory in the UK). I am considering a set of 16 Iridiums (NGK IFR5D10) to upgrade and ensure a nice smooth running engine. To avoid problems with possible thread seizure, should I envisage "greasing" the plug threads? If so with what type of lubricant?
P.S. I also have a 98' C240T with a M112 V6 and I discovered that it has the same type plugs as in the M113 engine V8.

Changed the plugs on my W202 a couple of months ago (M112 engine) and my Indy said not to use grease on the threads as they can cause problems in the future. (He said the grease can act like a bonding agent when it gets hot, so has the opposite of the desired effect).

He said, I should just dab a bit of engine oil around the threads.

 

[kwakdonut]

No lubricant is normally necessary as the plugs should be torque loaded so applying engine oil etc will actually over-torque the plugs and make it more likely to seize in!

I used to use a little Copaslip on the threads but generally don't bother these days (not on my diesel obviously, but on my bike!)

 

[DRBC43AMG]

No lubricant is normally necessary as the plugs should be torque loaded so applying engine oil etc will actually over-torque the plugs and make it more likely to seize in!

I used to use a little Copaslip on the threads but generally don't bother these days (not on my diesel obviously, but on my bike!)

Yes, naturally I will torque load the plugs as per recommendation, like I do with most of all the nuts and bolts on the car.
Would a bit of powder graphite on the threads be recommended?

 

[kwakdonut]

Yes, naturally I will torque load the plugs as per recommendation, like I do with most of all the nuts and bolts on the car.
Would a bit of powder graphite on the threads be recommended?

I wouldn't.

As Olly has already pointed out, steel plugs in an alu head=dissimilar metal corrosion. Adding graphite to the equation could just make it worse!

It's up to you though. As I said, I have used Copaslip in the past with no problems. Certainly makes removing the plugs easier, I just set the torque wrench slightly lower to compensate.

 

[kwakdonut]

Taken from Wikipedia, subject:Graphite....

'.....It is also corrosive to aluminium in presence of moisture. For this reason, the US Air Force banned its use as a lubricant in aluminium aircraft....'

 

[DRBC43AMG]

I wouldn't.

As Olly has already pointed out, steel plugs in an alu head=dissimilar metal corrosion. Adding graphite to the equation could just make it worse!

It's up to you though. As I said, I have used Copaslip in the past with no problems. Certainly makes removing the plugs easier, I just set the torque wrench slightly lower to compensate.

Fine, I'll either leave them dry or smear some copaslip and apply a lower torque rating as you suggest.
Thanks!

 

[OzC36]

DRBC43AMG,

You might consider staying with the Mercedes/AMG recommended plugs and wires...cheaper, safer and more reliable and better performance.

If better results were available from "upgraded" plugs and wires, you can bet your last dollar that AMG would have jumped upon that long ago.

Just a passing thought from an AMG owner...

 

[jefrs]

A little copper grease will stop steel/aluminium diffusion bonding whereas graphite and mineral grease will burn on.

Plugs generally have a compression washer, essentially a spring that will seal to the correct tension if applied with roughly the correct torque. You get a couple of goes out of them but once they are flattened they've had it and putting that plug back in is almost guaranteed to seize in.

Are not the MB plugs triple-electrode? - I used that type for years on the Volvo for improved performance, smoother with better bottom-end power. They're not adjustable but have a much longer service interval.

 

[markjay]

This is a known discussion - to copper-grease or not to copper-grease spark plugs (and wheel nuts)?

Personally I was in favour of not greasing, but then I changed the spark plugs on my Vauxhall Omega V6 and the original plugs (factory-fitted by Vaxhuall's engines plant in Ellesmere Port) when removed had ample amount of copper grease on them - so I decided to follow suit.

See pic18

Omega Owners Forum - Spark Plugs Change 2.6/3.2 V6 (2.5/3.0 similar)

For those of you who removed original fitment MB spark plugs, would be interesting to know if they were bone-dry or - like my Vauxhall - greased?

 

[johnpidge]

Had my 16 plugs changed today - by Colin Ferns in Richmond - Bosch FR7 DPP33's plugs £126 labour £187 plus the vodka and tonic - was expecting worse - 85k now on the clock I've done about 6k and I'm not sure when, if ever the previous owner changed them. Difficult in the traffic at 6pm tonight to say if it runs any better - a smidgen smoother maybe???

Won't be doing that again for a while!!!

 

[jefrs]

My impression of these triple electrode plugs, based on long term use of them on the Volvo was that they are that good, that you hardly notice when you do retire and change them. But I did notice immediately when the garage put ordinary plugs in on one service.