kastnna

Hi guys,

Changed out my spark plugs the other day. Used a torque wrench set to 20nm, no diaelectic grease, and the OEM bosch plugs were pre-gapped, but I double checked them anyway.

Anyway, after changing them, I cranked the car, got no CEL or skipping or anything, and gently revved the engine to 2500 rpms. No problems. Turned the car off and went to bed.

Yesterday, I crank the car and drive a mile down the road to the nearest highway. As soon as I hit the acceleration ramp, I go WOT. a second later, I hear a sound like a shotgun, followed by a repeated knocking noise, and a squeeking noise that sounds like a belt slipping. CEL begins flashing and the car has almost no power (I'm guessing it is in limp mode). CEL is now solid and car stalls at idle. I barely made it the mile back home.

I open the hood and begin removing coilpacks. Turns out the middle spark plug on the driver's side bank has exploded. Maybe I cracked it when installing, but like I said, I used a torque wrench. Anyway, the plug threads are stuck in the cylinder and I recovered most of the plug internals and ceramic coating but I've got no idea if anything fell into the cylinder.

What the hell do I do now? It's 60 (interstate) miles to the nearest dealership. Is it safe to drive? Should I even start it? I'm afraid to even drive to autozone to have codes read.

Thanks

kastnna

correction: TWO plugs exploded! Same middle cylinder on the passenger side also went boom. So I'm guessing that's cylinders 3 and 4.

phister

I wouldn't drive it if I was you. I would get it towed to a good Indie shop and have them check it out. You can borrow an OBII reader from autozone and read the codes and return it when your done.

kastnna

It's being towed now.

Unfortunately, there's no good indie shop close to me either. I ordinarily use Jonathan Hodgman at Blue Ridge Mercedes in Atlanta. He's excellent, but nearly 120 miles away. That's one hell of a towing bill.

All the same, I'm pretty sure it's my fault. I think I overtightened the plugs, even though I used a torque wrench.

mleskovar

That shouldn't cause plugs to "explode". Maybe you cross threaded them and the torque you were reading may have been accurate but the plugs weren't really seated. Can you be more specific what "explode" means? What was the plug number/type you installed?

d1no

Yeah I dont get how they can explode man.. Can you post pics of the plugs.. and the make and model of the plugs

kastnna

This is what I mean by "exploded"...



The NKG plug on the top was what was in the car prior to the replacement. The two on the bottom are the result of my recent problem. Turns out that all 6 plugs were damaged. Only two of them were so badly "exploded" that it was visibly apparent. The other 4 looked good when seated in the cylinder but upon removal it turned out that the ceramic and internals had separated from the threads and the electrode. We were able to actually remove 1 of those 4 plugs whole, but it was still damaged. The ceramic spun freely from the threads.

The rubber boot on one of the coil packs was actually blown apart, like elmer fudd's shotgun when Bugs Bunny sticks his finger in the barrel.

The plugs are Bosch Platin (platinum) number YR7MPP33. They were the ones recommended when I put the make model and year of my car into Autohausaz. They claim they are OES (not OEM). As a matter of fact, they are the only plugs available on Autohausaz for an '06 c280 272.940

I'm definitely no master mechanic, but I'm not an idiot either. I'm pretty sure I know how to work a torque wrench (90 degree force, no cheater bar, no grease, only leverage from the handle). I'd feel a lot better if I didn't do this. But I'm not convinced yet.

laneshift

I'm sort of leading towards mleskovar's explanation. You used the torque wrench for every plug, and let me tell you, I had the worst time fitting even my regular wrench (which is smaller) into the engine bay, near the rear of the engine, to change out my plugs in my c240. I found it very easy to cross-thread.

Let us know how it goes, good luck!

P.S., I just saw the picture. Looks nasty.

kastnna

I COULD have cross threaded, but I'm not sure.

Each plug was installed using a spark plug socket and a 6" ratchet extension. No ratchet was used at first. I installed them all by hand by simply spinning the ratchet extension between my fingers. They all went in effortlessly. I only involved the torque wrench after hand tightening.

And, as I said, I managed to remove one plug completely although it was damaged. There didn't seem to be any sign of cross-threading on the threads. Doesn't seem likely that it would be the only one not cross-threaded and yet it still suffered damage.

We'll see.

Glyn M Ruck

I've never seen a plug fail like that. You screwed up man - sorry. Do not drive!!!

johnand

Based on those pics, it looks like the new plugs electrodes are longer and possibly the wrong replacement. I suspect the pistons may have contacted the plugs.

FrankW

+1, but WOW that I've never seen.

and yes, you might have debris inside the cylinder.

those are #2 and #5 cylinder btw.

Glyn M Ruck

Yes - plug protrusion appears too long!

kastnna

I'm trying to remain calm and not jump to conclusions, but it's hard to sit around and wonder if I'm responsible for massively damaging my engine.

If it turns out that autohaus sold me the wrong plugs, I'm going to enter a world of pissed-off that the likes of which have never been seen. These were the ONLY plugs recommended for my make and model of car.

I'll just have to wait and see.

e1000

yup, it looks like you got the wrong plugs. ouch that sucks.

e1000

It's ALWAYS ALWAYS a good idea to check and recheck parts, and finally, compare what you pull to what you're putting in. I know it's not going to make you feel any better, but there are so many rolling changes in these cars it's always hard to keep track.

LILBENZ230

Autohausaz doesn't always recommend the right things and not just about spark plugs and that's why I no longer use them. It's best to use RMEuropean or getmercedesparts.com.

I can imagine that this is going to be quite expensive to fix. Sorry man.

04mbc230

One word: WOW

91RS

Do you have a picture of your original plug(s)?

Glyn M Ruck

The original is the LH plug in the pic

Glyn M Ruck

+1

Glyn M Ruck

Pistons are a lot stronger than you might think. Hopefully once you have all the bits out of the combustion chamber they will have survived. A minimum of a boroscope inspection is required - otherwise the head or heads will have to come off.

Glyn M Ruck

There is something screwy going on here - the YR-7-MPP-33 has a 26.5mm reach & is the correct OE plug for the 2006 C280 M272.940-203.054

The plug on the left in the pic above clearly is of shorter reach (NGK?)

Where are the compression washers from the 2 new plugs? Even so they are longer.

I wonder if the shorter plug had suffered flame shielding & built up a hard carbon slug in the plug threads & when the correct length plug was fitted it shoved this into the combustion chamber & caused mayhem. This would seem unlikely??? I'm confused unless they were hopelessly overtightened.

I wish you well with this problem - something does not add up. The plugs you took out seem wrong & the new ones correct.

e1000

Looks like they fell off due to the threads not being there anymore. I've changed the plugs on my old C350 and I can tell you that the Bosch plugs I got were the same exact length as the MB Branded NGK plugs that I removed.

Glyn M Ruck

Yeah - e - something is wrong here. My car came with & I still run Bosch. But the 112 is of course twin plug per cylinder.

If the OP had bought plugs for this car from RMeuropean they would have given him YR-7-MPP-33 Bosch Plat. It's all they carry for that engine & in ROW it is the OE plug. We never see NGK plugs on Benz cars.