Brabus D3: Piston Failure - Repair & Causes

Please take a look at the following photos.

"Broken pistons in a Brabus D3 (220 CDI)."

After inspection, all injectors were checked and tested on a test bench.

The injectors are fine. The car has a mileage of 150,000 km. However, the owner states that this mileage was accumulated very gently. Do you consider this to be critical?

I would rather not rebuild the engine with this piston again.

Best regards, efistho.

I wouldn't let it run like that anymore - didn't Brabus increase the performance?
At the exposed areas (I think), the nozzle sprays onto the piston due to extended pumping – am I interpreting this correctly?

Quote:

Would you really want to rebuild the engine with that piston again?

"Me neither. Most likely, these are wear marks. Sooner or later, the piston crown might also be affected, which could then damage the cylinder bore. I would measure/have the cylinders measured and, if they still have sufficient tolerance, verschandeln out the graphite deposits and install new pistons (suitable for tuning) while simultaneously replacing the connecting rod bearings, or disassemble the engine completely and overhaul it."

Assembled in this manner, I would only offer it (if you are a business) with an exclusion of liability, including a written explanation. Don't forget to have it signed.

So, a Mercedes with a power box .
Did you install that tuning kit?
Could it be that the vehicle had already undergone chip tuning before the installation of the performance box (P-box)?
Because you can not only see clear traces of the injection spray at the top of the piston, but also at the bottom in the recess. That can't be healthy, and I can't imagine that Brabus would install such an aggressive power module.

The vehicle is an original D3 that was also purchased from Brabus.
The package includes a ton of accessories to customize your car, such as springs, rims, steering wheels, decals, etc.

The performance increase wasn't noticeably drastic during driving, especially since the owner is more of a "fuel-efficient" driver. I removed the head for other reasons and was somewhat concerned about the wash marks on the pistons and the cracks I saw.

I assume that the standard Brabus control unit is installed, but I have not verified this.

Actually, this is a good example of why extending opening hours with the CR system is a bad idea.

I don't have to offer a warranty yet when assembling things with friends.

If I do something, then I do it with proper quality.

Take another look at the turbine now, and then I'll decide what to do about the patient.

Thank you for your statements.

Hi.

Regarding the pictures, I completely agree with what previous commenters have said.
But I always find it a bit strange when someone asks for help, but then you get the feeling that you're not allowed to know everything.

Why did the head have to come off? Maybe someone still has a glimmer of an idea that everything is somehow connected.

Greetings.
Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Sorry.

You are allowed to know everything.

The head had to be removed because the owner of the car was trying to close the EGR valve.


A foreign object prevented a valve on the fourth cylinder from closing properly, resulting in only 5 bar of compression.

The local "Friendly" mechanic diagnosed a faulty injector.

Subsequently, all of them were disassembled and shipped for overhaul.

They returned with the note: "No abnormalities found - all OK, cleaned and inspected."

The car came to me after another day of diagnostics with the injectors.

Unfortunately, I cannot translate that word because it does not appear to be a recognized word in the German language. It may be a misspelling or a made-up word. If you can provide more context or clarify the spelling, I would be happy to try again.

I completely agree with my predecessors. This is the typical (CR - Common Rail) tuning issue: increasing fuel quantity by extending the injector's opening duration, which causes the spray to hit the edge of the combustion chamber depression. This creates a pressure spike and heat input, but heat dissipation is poor due to the small geometric surface area of the edge. This can lead to stress cracks and often results in needing a replacement part, even with relatively low mileage.

Best regards!

Rainer also sells pistons with a larger combustion chamber as well.
Could one slightly ream or mill the inner edge of a high-quality combustion chamber piston without encountering strength issues, achieving the benefit of improved thermal freedom for the fuel jet (reduced tendency to crack) and a slight reduction in compression?

I have now been instructed to reassemble the car as it is.

Interestingly, all four valves in the fourth cylinder cannot be sealed properly.

The valves were removed and inspected for damage. Re-grinding them also didn't help. However, it seems unlikely that a relatively small foreign object could have caused such significant damage to the valve seats. There is nothing visible on the seats themselves.

This just confirms my opinion that assembling this "junk" is really just a smokescreen.

Unfortunately, I can only intervene to a limited extent; the owner's will is their kingdom!

"efistho" (This appears to be a single word with no apparent meaning in common English vocabulary.)

Good morning.

Have you ever considered a head replacement?

Some companies offer this service based on the amount of work involved, meaning they only charge for what's actually done.

It's important to address what is actually defective, rather than making blanket statements about everything.

This can potentially save significant costs, for example, the cost of an AT head (Automated Testing Head) is 800 euros.

Repairs start at approximately €300, depending on the complexity of the work, and you're not forced to cut corners.


Best regards, Obelix.

How could the head be arranged like that?
What does the corresponding piston look like?
As I see it, the injection stream even hits the valve or the cylinder head.
Was the injector checked for its spray pattern?
Whoever has something like that reassembled clearly doesn't deserve to have their engine running.
I know that this is not your decision to make .

The piston from the fourth cylinder looks similar as well.

It is covered with small indentations caused by the foreign object.

Measurements of the valve seats have not yet provided any clarity.

I will try to document the further progress.

Unfortunately, I cannot translate that word because it does not appear to be a recognized word in the German language. It may be a misspelling or a made-up word. If you can provide more context or clarify the spelling, I would be happy to try again.

You absolutely must machine the valve seat and then grind it. You can see where the image isn't clear; so, machine it over to the other side and grind it again, otherwise the valve will burn out again!
The cylinder head looks bad, and the piston will likely continue to seize up, or even get stuck completely, given the current fuel injection situation.

teileklaus wrote:

Rainer also also sells pistons with a larger cavity, Could one potentially machine the inner edge of a high-quality CR injector nozzle

to create a slightly larger recess, without encountering strength issues, with the benefit of improved thermal freedom for the spray (reduced tendency for cracking) and a slight reduction in compression? }
Hello,

Without a suitable mold design and an analysis of the piston (by, for example, cutting it open), nothing worthwhile will come out of this.

Best regards, Rainer.

Rainer K. wrote:

teileklaus wrote: Doesn't Rainer also sell pistons with a larger recess? Could one potentially machine the inner edge of a high-quality CR injector nozzle to create a slightly larger recess, without encountering strength issues, with the benefit of improved thermal freedom for the spray (reduced tendency for cracking) and a slight reduction in compression?

Hello,

Without a suitable mold design and an analysis of the piston (by, for example, cutting it apart), nothing worthwhile will come out of it.

Best regards, Rainer}
In addition to the above, the piston might be anodized on the inside for better durability, which was the case with some of the early TDI engines. In that scenario, this protective layer would need to be removed.

Why would someone buy a Brabus and then only drive it sparingly? Is that realistic?