Broken Mystery Bolt found in 2007 530i

[maver]

So I recently had the eccentric shaft sensor replaced on my 2007 530i. That was about a week ago. Car has run fine since. Today I noticed an occasional rattle coming from the passenger side of the engine and looked around. The shelf below the engine was clean, but a broken bolt was lying there towards the passenger compartment. It was easy to push it off the shelf and onto the ground with a long narrow pole. Can anyone help me identify what it is from? It is a blue aluminum bolt with KX2 AL9 stamped on it. I don't believe it is related to the shaft sensor job as the bolts used to access that do not seem to be this type. The bolt is likely an M11 and is threaded all the way to the head of the bolt. I've looked over realoem and can't figure it out. Any guesses before I take it in on Monday?501810501813

[E39DaveE53]

No need to worry, N52 engines use aluminum valve cover bolts (actually alot of aluminum fasteners on a N52 engine) that must be replaced after removal. (Stretch bolts = 1 time use) Any bolt with a blue head must be discarded after removing. Usually half a dozen bolts or so pop the heads off while removing the valve cover.

[kaineb]

It looks like one of the bolts that hold the transmission, the upper bolts are a bit smaller than the lower. But BMW used these in several places so its hard to say.

[maver]

No need to worry, N52 engines use aluminum valve cover bolts (actually alot of aluminum fasteners on a N52 engine) that must be replaced after removal. (Stretch bolts = 1 time use) Any bolt with a blue head must be discarded after removing. Usually half a dozen bolts or so pop the heads off while removing the valve cover.

So you think this is a leftover/discard from the sensor replacement? I hope so as that would be a $0 answer! I looked things up at realoem and I don't think this is a valve cover bolt. I think they changed from aluminum to steel between MY '06 and '07. Are the valve cover screws visible without removing the engine cover? But I am totally armchairing this.

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It looks like one of the bolts that hold the transmission, the upper bolts are a bit smaller than the lower. But BMW used these in several places so its hard to say.
I saw a 3 series thread about a mystery broken bolt that turned out to be transmission. My search of realoem hasn't shown any M11s on the tranny, but my measurement could be off.

[E39DaveE53]

Unfortunately you would have to remove the valve cover to confirm all the bolts are in place. Do you know what size the head is? E10 is definitely vavle cover.

[E39DaveE53]

Where exactly was the bolt laying when you saw it?
Is your valve cover plastic or metal?

[maver]

Where exactly was the bolt laying when you saw it?
Is your valve cover plastic or metal?

Here are a couple of pictures of where I found it - it is by the white circle down below the engine - this shot is from the left side of the engine. The second is a zoom.
501832501833
It was probably about 3 inches from the back of the shelf protecting the engine compartment from the road. I believe the valve cover screws are shown in the first picture above the red gasket poking out from the engine? If so, those screws are a different size.

I retract the statement that my valve cover bolts are not aluminum. They should be. My car is an '07, but was built in April of '06. They were apparently still using aluminum bolts in early '06, switching away from them in October.

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Unfortunately you would have to remove the valve cover to confirm all the bolts are in place. Do you know what size the head is? E10 is definitely vavle cover.
I can't seem to find my socket set to confirm.

[pcy]

Here are a couple of pictures of where I found it - it is by the white circle down below the engine - this shot is from the left side of the engine. The second is a zoom. ...

That's NOT left side of the engine. That is referred to as RIGHT side of the engine.
Left and right sides are referenced as if you are sitting in the car.

[Stephen Max]

501832



At the top of this picture there is a blue headed bolt that looks to be the same size. Maybe that one broke when they were removing it and then fell down to where you found it.

[maver]

At the top of this picture there is a blue headed bolt that looks to be the same size. Maybe that one broke when they were removing it and then fell down to where you found it.

Took the car in today - got a "that's where it went!" from the mechanic. Apparently it broke while they were doing work, they couldn't find it, but it found its way to the spot I found it after driving around. There is a missing screw (not bolt) that attaches the air filter box to the frame on the "Right" side of the engine. They are replacing that now and we'll see if that solves the rattle.

[pcy]

The broken bolt (that's attached at the top of this thread) has nothing to do with air filter box.

I question the honesty/competency of that mechanic.

[maver]

OK - resolved - this was a motor mount bolt. Attaches the magnesium bracket to the motor itself (and the actual rubber mounts) with aluminum bolts.