BRABUS M104 3.6-24 pistons rings failure

[Brabus 3.6-24]

Hi there.

I just riped apart my engine to get to the bottom line of my oil cunsuming problem.
3-4 L / 1000 Km.

I found the pistons (compresion rings) where broke.
Why is it that this could have happend?

The cylinder is looking great wthout any marks, edge or damage.
Now of cause the pistons rings havenīt got any use when broke, becuase they donīt have the presure against the cylinder walls any longer.

But could this just happens because the engine is worn out, (the cylnder walls is still looking realy great without any top edge and the bore strukture is still there, so no worn out cylinder walls.
and engine have only 180K as told. on the clock.

BRABUS tells that you can only go for the Castrol Edge/RS 10W/60 engine oil.
But the former owner didenīt pay this any attention and just put in what ever oil he could found at a disount price.
The rings look very dark and "hot" but not worned out, but I donīt know how they should look. but I know each ring is suposed to be in 1 piece and not several
So would it just be a simpel job to get new rings on the pistons and then use the right oil or should something more be done?
I have the head of, så ofcause this is at the shop for a rebiult/check.

But what could have caused the rings to brake (wrong oil or wear out or something else)
and should new rings just be fitted or is there something else to be aware of?

[Pagz]

Sounds like you may have had some unwanted combustion conditions,possible detonation or preignition will cause damaged rings like that.

What spark plugs are you running?...are they the right temperature?.

Poor fuel may have played a part also,do all 6 pistons have broken rings?

[Brabus 3.6-24]

poor fuel is not the isue I think, here in my contry we general have very good fuels.

Im always running octane 95 as I should.
And the spark plugs are acording to BRABUS to be the Bosch F7DC

But you might got something right becasue the spark plugs looked very poor and I just changed them resently.
my car runs with catalyst and the lamda sonde o2 sensor.
So it would be nice to check if this work as it should.
But I donīt think that preignition is the cause because it runs with knock sensor as well and all the electronic works, I have never had any problems with faulty engine electronics or bad running engine conditions.

Until now I can see that all the pistons has some black "stuff"/oil on the tops and I only have taken 2 of the pistons out to check.
but all my valves was covered in black smokey "stuff" so it has been from all the pistons that the oil has been burned.
so my guess is that it is all the pistons that has problems.
therefore my guess was on wrong use of oil?
but I have the opputunity to run on 98 or 99 octane, it is just very pricy compared to the 95 and the brabus instruktions tell that 95 is ok but a minimum to run on, sp generaly it should be ok.

maybee the compression is to high? or simply the pistons rings where just worn out? I realy donīt know, but im realy nevous if I put it all together with new rings and the reson is still there and then it will only last few Kilometers

But the fuel mixture should be checked and the O2 sensor deffently checked if it works as it should.

Any ideas else?

[c280nz]

run the highest octane fuel you can get,
if its 98 then run that, its better quality and you should get better mpg out of the fuel as well as a better engine.
and if anything run one step cooler plug.
at some stage the previous owner may have run low quality fuel and ruined the rings before you got it.
if i could easily get race fuel here that is what i would run, but with the problems you subscribe i would definatly go for the highest octane fuel you can get to help the problem.
like pagz said
from logan

[Brabus 3.6-24]

first of all, the fuel quality here is defently not a problem ever.
The octane has always been keept above the limit of 95 so no problems there im sure.

But now the pistons are at the shop for a check up, and he dident realy had the time to check it through when I was there, but a quick look he said it looked like the rings where just worn out and then they brake into pieces when the tolerences is getting to big, because the rings can rock up and down every time the piston changed direction and this makes it brake into pieces.
But he said that he would take a closer look to morrow to find out more about it with his measurings tools.

He was absolutely sure that bad fuel or wrong low octane deffently not could have casued this, we are not in Rusia he said

I talked to another Mercedes mecanik that have been there since they intruduced the W123 and he had never ever come acrossed broken pistons rings but again he said this engine runs with BRABUS configuration so this is not a fuel isue or bad O2 sensor or to lean mixture isue.
It has only something to do with worn out rings and/or pistons.
BRABUS uses other pistons and those are not as good as the Mercedes Pistons even though they can handle more power they are not as strong as the original pistons that will last a lot longer.
So his statement was that its mainly because of wear nothing else.
But he would just by new pistons and then fit them and of you go he said.
And he has got a lot of these engine in his hands trough his time.

But as many opinions as possiable is better so please post some more idéas or comments of what I have been told by those people

[c280nz]

what paul (pagz) and i were refering to is that possibly your piston rings could have been damaged by pre-ignition or detonation,
there is a few things that cause this:
to higher compression ratio
and to advanced ignition timing
another can be from build up of carbon etc in the combustion chamber.
but these all have to do with fuel quality, that is why i bought it up.
ignition timing is normally limited by fuel quality, the better the fuel quality the more advanced you can run, hence more power,
as a general rule you want to be as close to detonation/pre-ignition as possible without it actually happening.
there is more things that can cause this but these are the most common 2.

i only put that up for an explanation for you of why we said this.

but you engine builder sounds clever and he is probably correct that it is from a worn engine.

and as paul said, is it all 6 pistons with damaged rings?

[Brabus 3.6-24]

Sorry if I sounded ungreatfull for your help.

It was just because this engine runs with variable ignition and knock sensors, so even though the compresion wuld be high, then the ignition would just retard the ignition to a point of where a preignition is not happening. its a M104 engine 3.0-24Valves (300E-24)

But i preignition could of cause also happen unpredicted but then not in al the cylinders and then the engine would run bad all the time wich is does not. (please correkt me if im wrong)

But it is deffently strange why they would brake a piece of them here and there.
The oil rings looked ok on the 2 pistons that we pulled out. I will will pull out the rest on Monday.

[Pagz]

Originally Posted by Brabus 3.6-24

poor fuel is not the isue I think, here in my contry we general have very good fuels.

Im always running octane 95 as I should.
And the spark plugs are acording to BRABUS to be the Bosch F7DC

But you might got something right becasue the spark plugs looked very poor and I just changed them resently.
my car runs with catalyst and the lamda sonde o2 sensor.
So it would be nice to check if this work as it should.
But I donīt think that preignition is the cause because it runs with knock sensor as well and all the electronic works, I have never had any problems with faulty engine electronics or bad running engine conditions.

Until now I can see that all the pistons has some black "stuff"/oil on the tops and I only have taken 2 of the pistons out to check.
but all my valves was covered in black smokey "stuff" so it has been from all the pistons that the oil has been burned.
so my guess is that it is all the pistons that has problems.
therefore my guess was on wrong use of oil?
but I have the opputunity to run on 98 or 99 octane, it is just very pricy compared to the 95 and the brabus instruktions tell that 95 is ok but a minimum to run on, sp generaly it should be ok.

maybe the compression is to high? or simply the pistons rings where just worn out? I really donīt know, but im realy nevous if I put it all together with new rings and the reason is still there and then it will only last few Kilometers

But the fuel mixture should be checked and the O2 sensor deffently checked if it works as it should.

Any ideas else?

How long have you owned the car for?,were the spark plugs you removed the same as you reinstalled?
oil will make a mess of everything in the chamber,it will be heavily carboned,iv been told oil in the chamber increases the chance of detonation too.

I find it hard to imagine oil or general engine wear as being the cause of broken rings,that is assuming the rings are a reasonable quality!...but im no mechanic so ill leave that one for yours

What is the wear like on the piston skirts and around the top thrust side? is the ring to ringland clearance excessive at all?

Fuel quality is an interesting thing,i mean...who really knows what your getting and if the car is not used for a few weeks the grade can drop significantly...if your like mine and doesnt get used for 3-6 months i tend to play it safe and dump off-smelling bial green/yellow looking "98 octane" from the tank each time to avoid problems.

Knock sensor ignition retard is an interesting thing too...have thought about getting the knock sensor add-on motec does for its ECU range(utilises the OE sensor)...but its so damn expensive!...anyways,the thing that gets me about this system and this is just a personal opinion...is that for it to work preignition must happen...now generally it happens mildly and this will be picked up and timing retared to a suitable level...however,what stops this suddenly happening at high RPM when that spark plug or piece of carbon gets hot enough to cause ignition at the wrong time,sure the ecu will pick up the problem,but the ring/headgasket damaging pressures have already occured!.

I remember the day i brought my car...the owners said that i should run 96 as they put 91 in it and it made all sorts of funny noises under power...back then i didnt realise the significants of that comment,but it has some merit in the fact that very poor(audible inside the cabin) combustion can still happen with Knock control in place.

Could you get us some pics of the pistons? =)

Cheers,
Paul

[JayRash]

Well, i don’t think its detonation that broke the rings, no one will ever keep flooring a car that’s making enough knock to break the rings.
I mainly say the pistons need to be measured up, as most prolly they had shrunk with heat and age causing excessive piston slap. Now that would play havoc with the rings.
And are all the rings broken?! or are they just brittle??
If its the second option it could be that the car had overheated seriously at one point in its life baking the rings. or the car had been running leaner than it should, which over time also turns the rings int crackers.

Also don’t forget that excess oil escaping worn rings will increase compression and break a ring or two in the end, like i broke my compression ring on my boosted M103 from excessive water injection. you wont have hydro lock nor knock usually just excessive increase in compression on the rings. but usually in this case its a compression ring that cracks and not the oil ones, both together

[Pagz]

Originally Posted by JayRash

Well, i don’t think its detonation that broke the rings, no one will ever keep flooring a car that’s making enough knock to break the rings.
I mainly say the pistons need to be measured up, as most prolly they had shrunk with heat and age causing excessive piston slap. Now that would play havoc with the rings.
And are all the rings broken?! or are they just brittle??
If its the second option it could be that the car had overheated seriously at one point in its life baking the rings. or the car had been running leaner than it should, which over time also turns the rings int crackers.

Also don’t forget that excess oil escaping worn rings will increase compression and break a ring or two in the end, like i broke my compression ring on my boosted M103 from excessive water injection. you wont have hydro lock nor knock usually just excessive increase in compression on the rings. but usually in this case its a compression ring that cracks and not the oil ones, both together

Good points Jay!,it would be really interesting to see a pic of where piston wear has accured!.

[Brabus 3.6-24]

Here are some pictures that I toke just now.

I hope they are good.

To my own opinion, the wear is not on the side skirts of the piston but mainly on the rills where the rings are seated and the reason I think that is because the former owner used a wrong oil so the pistons rings where burned do to the oil not performing at high temerature.

BRABUS write that ONLY Castrol RS 10W/60 oil must be used.
because of the high stroke of the engine, the pistons and rings will now have a much higher speed/movement at the same 7000 Revs.
therefore this oil must be used to keep up with the heat.
And if you use a "standart 10/40 oil" that is not tempature compettetive, then my tought is that you will end up with burned pistons rings that will at the end give up and brake up.

The piston rings can here bee seen and the lower compresion ring had a small piece broken of in both ends og the ring, therefore the gab is videre than on the top ring.

on the bottom end of the piston "skirts" there is no wear at all, you can still se the strukture of the pistons texture witch I belive would have been gone if any wear hade made its way.
A shrinking piston sound interesting, I have never heard of such thing but ofcause this sounds possiable.

Please be aware of that during transportation of the piston it has got some dust on it.

Please tell me what you think.

[Brabus 3.6-24]

Here are some pictures of the engine as well.
Again a lot of dust looks realy nasty on the pictures but itīs just dust nothing else.

[Pagz]

Thanks for the pics!
Interesting style of piston,has a much deaper valve pocket than stock for that higher compression!...most of the newer piston designs Iv seen dont make contact under the wrist pin,what year is your engine?

Brabus use a different style oil control from the usual mercedes ones iv seen on these engines,looks very robust!,and a bit clogged up?are you planning to replace the rings with brabus parts?.

As you say the wear on your skirts looks very minimal!,also the wear between the rings looks minimal too,if the ring lands are not worn and the bore shape is good you could simply re-use the pistons with new rings!?

Edit:
Based on how my stock pistons looked when i removed them these look like they have run farily hot??



Paul

[Brabus 3.6-24]

thanks for your comment.

The year of my engine is 1991 but the bottom end say M103
But the engine is deffently the M104 with 24 Valves, so I guess this is because brabus have changed the original engine to this monster.
brabus say that they do both (change the engines "in old days" or do the job on the original ones)
But my org. engine were with a M104 number, so I guess that brabus goes with the M103 bottom end because its stronger in some way

The reson for the black smog on the piston is just because of the oil that have been burned over time. but on the side there is also a purpel dark colour so at some point it have deffently been very hot.

To my opinion it is also just a matter of new rings, but other people that have looked at the pistons with there hands say that you can not see with your eyes if the gap it to vide for the piston rings to sit correkly.
This should be measured by a specialist/shop and this is done to day, så I hope I will have good news to day

But I will deffently go with the brabus choice of rings, but of cause not bye them there as they are dobbel the price.
The shop who check the pisons can order them direktly from the brabus supplyer.
The pistons are Smith & kolben pistons, but to another old mercedes dude, it would be foolish not to change the pistons as they come with fresh rings, because the price is almost the same and then there is no doubt or overlooked problems that will return.
but he would only do this because of the brabus option, if org. mercedes he would never do that becuase they have a very different wear and will never have problems like this as standart configuration.

Lets see what the Shop comes up with to day

[Pagz]

Its alittle older than i first thought,also just a hunch but Its very likely the new rings supplied from brabus will be of a higher quality than the ones first fitted!
Im not too clued up on how strong the bottom ends are or what the main differences are with the 103/104,brabus must have done it for a good reason!.It will be interesting to see what the ring lands are like,and judging by the purple colour you mentioned Jay could be right about the lean mixtures cooking the rings over time.

I agree with your old mercedes dude!,The OE Mahle Mercedes pistons used in the M111/104 etc are very nice,and i admit i was very wrong for once thinking a forged piston could do a better job at the horspower im running!.

As a comparison to the wear you have heres one of my M111 psitons with 100k km's on it,from the wear notice the skirt wall has a concave shape unlike other flat tappered skirts,also there is no wear around the ring area at all!