Rafichicago

Hello forum members. It’s been a while since I’ve posted here but lurking from time to time😉
I am lucky to have wife working at local Mercedes dealership and I also know one of the best techs there. He had done multiple head bolt replacement. It’s not a definitive answer to the issue but I’ll tell my story. We decided to do this job Mercedes - way meaning head removal. He had replaced head gaskets as well as lifters and some other things “while in there”. Injectors were replaced with a new ones spark plugs etc. Cams were in great condition but my wagon has under 70k miles so not all that high.
We went with head removal instead of one by one method since he had an instance on his own car that after removal of one bolt coolant mixed with oil. Do not ask me how he find that out. I did not ask. Anyway. Here’s what we found out. He had a broken bolt from 07 ml63 that we compared to the bolts in my 09. There were definitely 3 different bolt types used by Mercedes in this application. One is the newest E-torx two others are regular toed bolts. What’s interesting his 07 required larger socket if I believe e55 and there were e50 in my car. Both old style “female” type. Unfortunately I did not take a photos in the shop however he kept one of my bolts for comparison. All in all I’ve got more than a decent deal with this job I thought that someone a while mentioned that Mercedes probably used 3 different bolt types. We really think that because of that some cars might run longer without this issue than the others since there is less material left thus making bolt weaker if that makes any sense. Bolts requiring larger socket lave less material holding it because it takes bigger hole to fit a bigger socket. This leaves less material holding bolt together at the spot where threaded rod meets the “bolt head”. I am not a native speaker so I’ve tried to explain what we think to the best of my abilities. Sorry for the long post. I just thought I will post our findings.
good day to everyone
attached are some photos. Last one is one of the injectors. It’s clean where it should be however it has some gunk above the nozzles.

Plutoe

whats the big todo the tips look great

Yuille36

Your head bolts look about average for the model year, my head bolts looked about the same as yours when I had them replaced, out of abundance of caution.
But when we explained mine more closely, they really didn't need replacing, and in great shape. But it's all about the what if, and not when.

Rafichicago

I’ve done mine just because I had an opportunity to do it with heads off for quite a discount from regular dealership pricing. Otherwise I wouldn’t touch them. Lifters however we’re a different story. While surface on some looked ok, on most others there were early signs of wear. If you’d take a metal pick over each ones surface you could feel that they’re not perfectly smooth anymore. Those required replacement, since they are primary cause of camshaft wearing down prematurely.

Yuille36

Totally agree, my cams showed very little wear on the lobes, so we left those alone. But we did change out my lifters for the SLS ones, thought about the SLS BS, but couldn't justify the added cost.
I had one really bad looking headbolt, but I'm glad that I spent the money to have them change out. Now, never have to worry about them again.