Spark plug change - specialist?

[fabes]

Despite a thorough maintenance history (Inc ATF changed) it seems the plugs haven't been done on my new car.
Due on both age and very shortly mileage, is this a big or specialist job (M276 3.5l)?

I read some threads that suggest it is and a £260 quote indicates this, but I just wanted to sensor check as I do want to get it done or get it done with a mate.

Any advice appreciated

 

[Bobby Dazzler]

Despite a thorough maintenance history (Inc ATF changed) it seems the plugs haven't been done on my new car.
Due on both age and very shortly mileage, is this a big or specialist job (M276 3.5l)?

I read some threads that suggest it is and a £260 quote indicates this, but I just wanted to sensor check as I do want to get it done or get it done with a mate.

Any advice appreciated

I recall that on some V8s it can be awkward to get to the rear plugs but as long as they’ve not been in there for a very long time (and therefore reluctant to come out) I can’t see why a competent mechanic couldn’t do this. A Mercedes Specialist might have more experience of dealing with reluctant plugs at the rear of engines though.

 

[Petrol Pete]

This is an old one but straight to the point.

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[fabes]

Cheers but it's not specific to the (apparent) issues my V6 presents. (and yes I'm being picky)

I fear I will just have to accept that it's a £250 quid job....

 

[whitenemesis]

You have Olly just down the road in Horndean at PCS, give the guys a ring for straight, honest advice?

 

[neilrr]

HOME | MBS Southampton Ltd

www.mbssouthampton.co.uk

 

[AMGeed]

^+1 for MBS.
I think the OP already has his services done by Cole at MBS.

 

[Jobsworth]

I’d strongly advise using genuine Mercedes plugs for these direct injection engines. Plug clocking is important, and in my experience MB plugs clock correctly at torque everytime. Aftermarket ones often don’t.

https://f01.justanswer.com/eurotec/cc33a0af-2931-48a4-a301-1f7e491b3702_79551.pdf

Details here.

 

[E55BOF]

...in my experience MB plugs clock correctly at torque everytime. Aftermarket ones often don’t.

You will have noted that in the pictures, the incorrect plug is not actually the correct length, so it's hardly surprising the indexing was wrong! There's only on thread on a spark plug, so if it is the correct length it will be indexed correctly if the tightening torque is correct.

If you can get your hands on an old plug, you will probably find the manufacturer's designation on it, and can simply buy a set of those. All the extra you get for the extra cost to buy one in a Mercedes box with a Mercedes logo on it is the box and the logo.

 

[Jobsworth]

You will have noted that in the pictures, the incorrect plug is not actually the correct length, so it's hardly surprising the indexing was wrong! There's only on thread on a spark plug, so if it is the correct length it will be indexed correctly if the tightening torque is correct.

If you can get your hands on an old plug, you will probably find the manufacturer's designation on it, and can simply buy a set of those. All the extra you get for the extra cost to buy one in a Mercedes box with a Mercedes logo on it is the box and the logo.

The length of the thread isn’t really relevant, it’s where the thread starts, or more accurately actually finishes compared to the position of the earth post. I always mark with a sharpie so I can check where it sits when fitted. MB are always in zone. A couple of times I have tried aftermarket and they are variable. MB plugs aren’t actually significantly more expensive.

 

[fabes]

Cheers all.
As Roger says it is MBS I use as I am only 2 miles from them, plus they are obviously good, but the quote for £250 quite took me aback. Parts I get but it's a 2 hour job on mine....?

Have just helped on an MGF (bugga to access) and money doesn't grow on trees, so I wondered....

Still, with TPMS no.4 also playing up, I think I need to flush the moths out of the wallet and book in.

Will just wait for pay day

 

[E55BOF]

The length of the thread isn’t really relevant, it’s where the thread starts, or more accurately actually finishes compared to the position of the earth post. I always mark with a sharpie so I can check where it sits when fitted. MB are always in zone. A couple of times I have tried aftermarket and they are variable. MB plugs aren’t actually significantly more expensive.

The MB document actually states: "The NGK plug does not have the correct thread length for proper indexing". The thread length is what determines the indexing; I don't see that as not really relevant. Your point is I think that It needs to be very precise, though, and an aftermarket plug might not be quite spot-on.

That's why I advised using the OE supplier's plugs. The saving might not be great, but I at least prefer not to spend money I don't have to.

 

[Jobsworth]

. Your point is I think that It needs to be very precise, though, and an aftermarket plug might not be quite spot-on.

Exactly this. The earth bar is welded on. The accuracy of that placement relative to the end point of the thread is critical. The quality control on genuine plugs guarantees this every time. Others I’ve encountered do not.
I still mark and check even genuine ones though. I don’t want to be paying for a piston.

 

[fabes]

Booked in for early June.

Got a big trip to the NW in mid June, so it makes sense

 

[MikeInWimbledon]

All good advice, especially from Bobby D. The point I’d add, explicitly, is to ignore the total cost and focus on the Labour and parts elements separately.

It’s when you think about the time alone that you can focus on exactly what they’re doing. And you can usually see how a specialist’s access to discounts on parts can help subsidise your Labour element.

 

[MrGreedy]

How many plugs does it take? Is it 6, or 12? And do they need to be platinum or iridum tipped. That's a bit more pricey than a normal 4 potter.

On my previous w203 with the 320 V6 engine, it has 12 platinum tipped. 6 large and 6 small. I ended up changing myself with Merc plugs, which I suspect was the first change at 90k miles when I bought the car. A couple were frighteningly tight, but some penetrant soak and a lot of careful back and forwards with the breaker bar eventually cracked them off.

 

[Dickster]

I’ve done them on my SL55 (all 16) and it’s not scary if you take your time. I had a few stubborn ones. Rather than risk stripping threads, and using a breaker bar, I ran the motor up to operating temp, and they then came out with ease.

 

[John757]

glad I read this.. wasn't aware of the indexing issue.. I will no doubt change my plugs in my 55 at some point myself... I presume the gap is set by Mercedes... I put some NGK Compatable plugs in my Gwagen 2 years and 2000miles ago , and the gaps were all wrong until I set them. might swap them out for genuine MB ones having read this.. Great advice.

 

[SL63Mark]

I did all 16 plugs in my SL55 a few years back, I do not recall indexing being an issue for that engine. (M113k). I think that it became a problem on more recent engines. I believe it is critical on the SL63 Biturbo. Mind you, I did use MB genuine plugs on the SL55, due to forum advice so may not have realised the reasoning for this at the time.

 

[Jobsworth]

That's why I advised using the OE supplier's plugs. The saving might not be great, but I at least prefer not to spend money I don't have to.

I had a moment to spare this afternoon, and needed to order some spark plugs for a w205 C63 4.0 biturbo that’s in tomorrow for service. I ordered the plugs from Mercedes, but thought I’d see how the price compared to three different motor factors that I regularly use. The best quote from those three was £11.25+vat per plug. 8 of required, obviously. How much do you think the genuine plugs were from Mercedes. A fiver more? Tenner?
No, the price I paid, £6.38+vat each. Who’d have thought it?