MB Service gone wrong - spark plug snapped!

[swift1]

Hi folks,

would like to get your thoughts and whether I need to worry!

My mother has recently bought an A170SE Auto on a 55 plate (W169) and was due a service. Booked the service at the local MB dealer (had a bad experience with local indy on my own car thought I'd play safe and go with dealer).

Just shy of £500, service includes, service A, brake fluid, combi filter, air filter, atf oil and filter, spark plugs and rear brake pads (is this a reasonable quote for an a-class?)

Got a call the morning I was supposed to pick up the car, saying while fitting one of the spark plugs it snapped off! he said the spark plug got cross threaded and the top of the spark plug is made of porcelain and is easily breakable! He said they've tried some tools to get it out but has failed and they will have to take the whole engine out and strip it down to get at it from the inside!

Is there anything I need to worry about as it sounds like a quite complicated job and they're opening up the engine - will they be causing any short or long term damage that will affect the life of the engine?

Is spark plugs breaking just one of those things that happen now and again to all good mechanics or is it a cowboy mistake? To my mind if its just like a screw that goes in at the wrong angle and you get cross threading you meet resistance very quickly and so you back out and try again. Only if you've lost your mind would you try and carry on and force the thing in - is this a correct analogy?

would welcome your thoughts on this issue,

Thanks,
Swift.

 

[nick mercedes]

Free rebuilt engine, happy days!

 

[Ted]

The top of the spark plug is made of porcelain and is easily breakable.
But that has no relevance to removing or fitting, unless the socket was so far askew whilst cross threading that it broke the porcelain.

IMHO that is simply bad workmanship or bad tools.

 

[adam1977]

I had a couple of spark plugs break on a V12 Jaguar engine, but that was from taking them out and it was a very awkward job the metal part that screws in stayed intact and came out easy enough.

It sounds like sheer incompetence really on the dealers behalf; as long as they don't expect your Mom to fork out for their stupidity then that's fair enough.

 

[npuk]

Which main dealer is the car at?

 

[Sp!ke]

Sounds to me like they tried tightening up the plug with an airgun whilst cross threaded. I cant see any otherway that they could have snapped the plug whilst tightening it up.

I very much hope whoever is doing the remedial work is better trained/skilled than the monkey who did this.

I'm also not sure how getting to is from the inside will help with its removal though. More likely they'll be taking the head to a machine shop to get it drilled and helicoiled. I would refuse a helicoil and demand a new head along with a reliable mechanic to perform the task.

 

[grober]

Whoa!! So far all you have is their word for what has happened. I would want to visit the dealership see the car for myself and speak to the service manager minimum before anything is done.
You want firmly established

1. What exactly the problem is.
2. Why it happened- just to establish who is to blame here
3. Their proposed remedial action and why its necessary.
4. Who picks up the cost.


I don't like phrases like "the spark plug got cross threaded" spark plugs don't cross thread themselves the person fitting the plug does that!

 

[Uncle Fester]

Whoa!! So far all you have is their word for what has happened. I would want to visit the dealership see the car for myself and speak to the service manager minimum before anything is done.
You want firmly established

1. What exactly the problem is.
2. Why it happened- just to establish who is to blame here
3. Their proposed remedial action and why its necessary.
4. Who picks up the cost.


I don't like phrases like "the spark plug got cross threaded" spark plugs don't cross thread themselves the person fitting the plug does that!

Agree with that, and get it all in writing, as the dealership should cover the FULL cost of all the work, and provide a courtesy car untill yours is returned to you in the condition you left it in.

 

[iscaboy]

To break a spark plug by cross threading it is not easy, it is hard to do, unless you are a gorilla.

Speaking personally, I would accept nothing less than a new cylinder head, I absolutely would not accept the buggered spark plug thread being tapped out and helicoiled.

As other's say, complete refurbed engine and labour for free, plus free courtesy car in the interim.

 

[Ted]

Having criticised the mechanic, I have just remembered when I changed all the fluids on my G-Wagen, and cross threaded the gearbox (or transfer box) filler plug thread.

I really don't understand how I did it - easy access, easy visibility, and a really coarse thread - should be impossible, but somehow I did it.

In my case I realised really quickly, and some careful work with a tiny knife file sorted me out.

Oh, and for those who don't know, all filler/level plugs and drain plugs on a G-Wagen are exactly the same.
I love Mercedes engineering

 

[Sp!ke]

Having criticised the mechanic, I have just remembered when I changed all the fluids on my G-Wagen, and cross threaded the gearbox (or transfer box) filler plug thread.

I really don't understand how I did it - easy access, easy visibility, and a really coarse thread - should be impossible, but somehow I did it.

In my case I realised really quickly, and some careful work with a tiny knife file sorted me out.

yeah but...

In your case, you are not a professional highly trained mechanic and yet you quickly spotted the issue and fixed the problem.

In the OP's case, his car was allegedly being worked on by a professional highly trained mechanic (and charged highly for this supposed expertise) and yet somehow the problem wasn't spotted and said technician continued tightening until the plug snapped leaving it stuck in the cylinder head.

As per Grober, you need to get down the workshop and establish what is going on with the workshop manager.

 

[Uncle Fester]

It sounds like they let the apprentice do it, as it was "an idiot proof job"

 

[swift1]

Hi All,

Thanks all for a great and quick response.

It does appear from what you guys are saying that this a mistake that can only really happen if one is being extremely careless and reckless - given the sky high labour charges this only makes a mockery of the service.

I don't know much about engines - I know just the very basics i.e. spark plug ignites fuel/air in cylinder and pushes piston round. I take it, its the cylinder head where the spark plug resides.

They have provided a courtesy car and they did say off the bat that they will take on the expense of fixing it.

I don't want to name the dealer just yet as the car is there and don't want to jeopardise anything.

I will contact the service manager(SM) again and see if I can get a full breakdown of what exactly happened and what they are doing and get it in writing - the SM did try and blame the spark plug rather than the person! blaming it on the porcelain part!

But like many of you are saying the porcelain part has nothing to do with taking it in or out - I will pose this question to the SM next time I speak with him.

Thanks again for all the replies.

 

[trapperjohn]

Great forum this.
With the coaching from the side lines you will defo be a winner here.
A chat with the SM over a coffee and dropping in all the stuff asabove - re helicoiling and such like he will really sit up to attention. Whilst you can relax and let the forum take the strain.

Good Luck.
PS Bet you get whisked into an office to discuss this away from the public!

 

[davidjpowell]

It probably was the garage apprentice. Certainly the ex MB mechanic I now use tells me that the servicing was virtually always done by the apprentice, to leave the trained mechanics to deal with the more complex problems and diagnosis.


Good luck to the OP, but it does sound like the garage are being fair, and in this life things do go wrong. It's how we go about putting them right...

 

[jaymanek]

I wouldnt recommend the all guns blazing approach... mistakes happen... at least they have admitted it and are sorting it out..

If its only slightly cross threaded, a tap run through from the inside of the head should suffice. A helicoil is a perfectly sound repair too, as long as it is done expertly.

 

[iscaboy]

mmm

1/ helicoil can IN THEORY be as good as, or better than, a basic thread, especially a basic thread cut into a soft material such as alloy.

2/ one area where helicoil often falls over is, as it happens, spark plug threads, the thing to use there is something called a time-sert - ++ TIME-SERT Threaded inserts for stripped threads, threaded inserts, thread repair stripped sparkplug's, Ford sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts, Ford spark plug repair,

3/ fitting a helicoil PROPERLY is several orders of magnitude harder than fitting a spark plug, or any other fastener.

4/ Since this was done by an MB mechanic, then you are entitled to have it "put right", put right does not mean you have to accept a "repair", such as a helicoil. Put right means a new head.

 

[swift1]

tried to give the service manager a call to get a progress update and what method they're employing to fix things, the receptionist said he was "busy" and would call me back later, well they're now closed so guess I'll have to ring again in the morning.

Is that right, if they are using a helicoil or other thread repair, I don't have to accept it and can ask them to instead get a new head!? What if they're argument is that the repair is as good as if not better than new!? (Don't know for sure what method they're employing will find out in the morning and keep you posted.)

 

[iscaboy]

Is that right, if they are using a helicoil or other thread repair, I don't have to accept it and can ask them to instead get a new head!? What if they're argument is that the repair is as good as if not better than new!? (Don't know for sure what method they're employing will find out in the morning and keep you posted.)

Yes, you can refuse, put it this way.

I have two absolutely identical in every way V8 mercedes sports cars for sale.

One is 100% factory fresh.

One has had all 8 spark plug holes helicoiled.

Would you pay the same money for both, and have no preference of any kind for one over the other?

I should also note that the simple fact that YOU are having to chase THEM up for info is all the proof you need that they are screwing you and going for a cheap fix... maybe even so cheap as to helicoil WITHOUT PULLING THE CYLINDER HEAD and thus dumping metal swarf inside the engine, thus ****ing it completely.

 

[ecossebev]

If you are going to the dealership to discuss the issue with the SM, ask to see the job card and find out what exactly they are doing to remedy the problem. It should say what they are doing and what parts they are using.