Detonation issues = motor go boom-boom
I read on here that some of the 2003's had ring landing issues with the pistons which was kinda one of those "first model year" issues that was later worked out. When I pulled the pistons, they had obvious signs of detonation...which will kill just about any piston.
Here are my main questions...does anyone know what causes this detonation in an all stock motor? Is the detonation due to something else in the motor or is it all just piston related and was "fixed" in the +2004 models? Was the design of the pistons changed in the +2004 models or just the materials? Any other combustion chamber design changes to prevent any hot-spotting?
I'm surprised that the knock sensors didn't trigger the ECU to pull timing to save the engine if it was knocking that bad...but so much for hope.

For those wondering what I found, here are 2 pistons. Both experienced cracked rings and/or broken ring landings. I haven't pulled the rest yet but a couple others look like they were detonating as well so I'm sure at least one more will look similar:


Thank god it was under extended warranty.
They replaced with a brand new fully loaded crankcase from AMG.
$26k later, car runs strong, thank god for the warranty.
Didn't give any reasons for this. Just stated that landings failed.
I was not sure if this was a random or common problem on 2003 models.
Just hope now with the new crankcase put in June of 09, that it holds up for the long haul. Came with 1yr warr. from MB.
Sorry about the luck.




Thank god it was under extended warranty.
They replaced with a brand new fully loaded crankcase from AMG.
$26k later, car runs strong, thank god for the warranty.
Didn't give any reasons for this. Just stated that landings failed.
I was not sure if this was a random or common problem on 2003 models.
Just hope now with the new crankcase put in June of 09, that it holds up for the long haul. Came with 1yr warr. from MB.
Sorry about the luck.




14k for crankcase
another 12k for other parts, ton of seals, redoing the crank, and labor, etc....
That does not count the couple grand the borrower came out of pocket for various items that warranty did not cover.
Think it was close to $30k almost.
Heads usually hold up in this type of thing.
Mine were fine. just needed to be machined as they were being put on a perfectly new block.
Now there should be higher compression though

You figure once you blow the rings, not much compression happening where the valves and heads are so they should not be messed up too bad if at all.
I would also think those pieces would not make it into the pressurized combustion chamber, but rather fall below the piston??????????
I would definitely recommend the head work though if you were to tear down the engine anyways.
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EDIT: The heads appear to be fine. All the chunks of ring landing weren't actually missing when I removed the piston. They were still trapped between the rings...just not attached to the piston any longer.
EDIT #2: Yacht Master, I thought that I noticed a little louder blow-by on these cylinders than some of the others, but the tool I was using wasn't a true leak-down (no gauge, just a pressure fitting) and I was taking the optimistic approach hoping the motor hadn't shredded itself.
Last edited by kjlindgr; Feb 17, 2010 at 03:32 PM.
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I read on here that some of the 2003's had ring landing issues with the pistons which was kinda one of those "first model year" issues that was later worked out. When I pulled the pistons, they had obvious signs of detonation...which will kill just about any piston.
Here are my main questions...does anyone know what causes this detonation in an all stock motor? Is the detonation due to something else in the motor or is it all just piston related and was "fixed" in the +2004 models? Was the design of the pistons changed in the +2004 models or just the materials? Any other combustion chamber design changes to prevent any hot-spotting?
I'm surprised that the knock sensors didn't trigger the ECU to pull timing to save the engine if it was knocking that bad...but so much for hope.
For those wondering what I found, here are 2 pistons. Both experienced cracked rings and/or broken ring landings. I haven't pulled the rest yet but a couple others look like they were detonating as well so I'm sure at least one more will look similar:



That's what I don't understand. Even if the previous owner was running a low grade fuel and romping on the car in 100 degree weather. There is a chain of events that should occur. Knock detection, retard timing, if iat continue to shoot up, supercharger shuts off preventing further damage. This needs further investigation. I hope you get it all sorted out. BTW it's good to see someone willing to work on there own cars.
Looks like the ring land just collapsed? Ive seen severe detonation occur and it will actually start melting through the top of the piston on a corner. Then eventually destroying the rings. The top of your pistons "look" OK in the pics. Are you certain it was detonation and not inferior ring lands in certain 2003 models?
Last edited by Max.H; Feb 17, 2010 at 03:56 PM.

Anyone know if Mercedes has a transferable extended drivetrain warranty on these cars? Maybe I'm covered.
weak design fault in the engine or weak fuel being used ?
I only use 99octane shell OPTIMAX and mine is an 2003 with nearly 100,000 miles
One thing I would check is the ring gap on the second ring for any signs that the ends butted together. Also, I agree with dirty that most of those marks look like debris knocking around.
Sorry to hear about your trouble. Unfortunately we know little to nothing about intra-model differences on these cars, aside from what is clearly visible on the exterior/etc. I think something you may want to consider is that the car was previously modified, and may have run a bad tune/pulley/whatever setup. Tunes have a knack for getting around factory-imposed safeguards, unfortunately.
-m
The top of the pistons here don't show much melting just severe ring damage.
Im asuming it was acting up before you started changing things and now you can see why,you mentioned about having the timing off at one point,do you think that would of done this?
or was it not running good at all before you swapped the plugs and moved the timing.You could have the dealer update the ecu,they might charge an hour labor tho.
Any way the stealership could update the ECU without the car? I'm assuming not...but the car isn't exactly mobile at the moment.
KJ I am sorry to read this and see these pictures. What is the next plan of action? If anyone can build a new and strong engine you would be the person, I vote on sending your ECU to Kleeman and let Corey take a look at the tune on it and give you feedback.
Yasin




