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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > can somebody, ANYBODY enlighten me on whats happening to my BEARING LEDGE



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      07-19-2020, 06:27 AM   #1
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can somebody, ANYBODY enlighten me on whats happening to my BEARING LEDGE

Just discovered this on the top of my exhaust side bearing ledge. 2008 328i n52k, the plastic VC. Just bought this, my first bmw about 2 months ago. Decided to do the oil filter housing gasket, then decided to do the VCG and all that entails. Got the cover off, engine was a little sludgy, discovered an extremely faulty PCV diaphragm, bought the aftermarket repair piece and did a kick ass job on that since VC was off. Couple days later was finally free from work to put all back together, was cleaning off some of the oil sludge caused by said PCV and found these lil micro fissures on top of a few spots, and also these little pimple looking things on the Ledge on exhaust side. The pics look waaaay worse than to the naked eye, phone finally took some decent pics. I stopped there and didn't find anything else, going to finish later today....BUT WTF is going on here, looks like some kind of corrosion, I am new to bmw's so I'm still learning as I go, but I feel if the camshaft underneath was the cause the issue would be along the entire ledge and not what right now is random spots......any and all info is appreciated can't find anything thing similar online.... will update this evening if I uncover any more fuckery
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      07-19-2020, 12:49 PM   #2
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So what I think you are seeing is simply the cylinderhead casting. The cylinderhead is casted using a "lost foam" method, where the casting "core" is made from Styrofoam, yes coffee cup material. It is similar to how most jewelry is made via the "lost wax" method. The cylinderhead casting technique was invented by General Motors in the 1980's for the production of engines for the now defunct Saturn car division. What you are seeing is the imprint of the foam core on the casting sand. As the casting mold is filled with liquid aluminum, the Styrofoam is "lost" (melted away) as the hot aluminum reaches it, occupies its space and creates the part.

Here is a pic of my N52N (with the plastic valve cover) I took yesterday for a DIY. This is the entry for the t-stat hose to the cylinderhead. Notice how the head casting looks like a Stryofoam coffee cup.
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A manual transmission can be set to "comfort", "sport", and "track" modes simply by the technique and speed at which you shift it; it doesn't need "modes", modes are for manumatics that try to behave like a real 3-pedal manual transmission. If you can money-shift it, it's a manual transmission. "Yeah, but NO ONE puts an automatic trans shift knob on a manual transmission."
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      07-19-2020, 02:50 PM   #3
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Quote:
Originally Posted by Efthreeoh View Post
So what I think you are seeing is simply the cylinderhead casting. The cylinderhead is casted using a "lost foam" method, where the casting "core" is made from Styrofoam, yes coffee cup material. It is similar to how most jewelry is made via the "lost wax" method. The cylinderhead casting technique was invented by General Motors in the 1980's for the production of engines for the now defunct Saturn car division. What you are seeing is the imprint of the foam core on the casting sand. As the casting mold is filled with liquid aluminum, the Styrofoam is "lost" (melted away) as the hot aluminum reaches it, occupies its space and creates the part.

Here is a pic of my N52N (with the plastic valve cover) I took yesterday for a DIY. This is the entry for the t-stat hose to the cylinderhead. Notice how the head casting looks like a Stryofoam coffee cup.
Interesting....must say that's a little bit of good news thanks for the input...i also just installed that aluminum coolant fitting when doing my OFH.
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      04-09-2021, 10:19 AM   #4
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Did my vcg yesterday and saw the same issue on my exhaust camshaft ledge
https://pasteboard.co/JWxSZwQ.jpg

https://pasteboard.co/JWxTqvB.jpg

I had a misfire that traced to a small tear in a coil boot, followed by vodes for valvetronic system. Engine jumped and bucked when starting unless valvetronic sensor was unplugged. Replaced sensor and motor, noticed this . I assumed stress fractures but saw this thread.

Still unsure plan on possibly replacement.
Got parts from local u-pull lot. Lucked out, $20 for the motor, $10 for the sensor.

Car runs and starts smooth
https://pasteboard.co/JWxVDIe.jpg
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