Rocker arm fell off of valve. Trying to figure out why?

A6 All/ S6 All
#1

I bought an 07 S6 that was running rough and had a popping noise in the intake. I scanned it and found intake flap codes. I removed the intake and found:

  1. Large chunks of flaps blocking the ports
  2. The intake valves badly carboned.

I bought a new manifold and started cleaning the intake valves but found one of the I take valves not moveing stick shut. To investigate I pulled the valve cover and found the rocker arm off the valve and laying in the bottom of the head. Interestingly enough when I cleaned the that valve the one that was stuck closed was heavy carboned the valve working on that clynder was lightly carboned. I almost thing the previous owner was driving it like that for awhile. The valve does move freely and is sealing. Does anyone have any ideas on why this could have happened? I’m in the process of removing the engine to change the camshaft and rocker. Thanks!
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#2

Only thing I can think of is a plastic piece of wedged in between the valve and seat at high RPM causing the rocker to unseat??
I did have plastic wedged in my intake valve as well, but no rockers popped off thankfully.
I was going to ask if you will be changing cams due to the scoring but I see you are already doing that.
Sounds like you know what you are doing, any questions specific to camshaft removal let me know. I just resealed my lower carrier couple months ago.

#3

That is a good point and a very real possibility. If a piece of plastic from the intake wedged open a valve, the valve spring would not be allowed to keep pressure on the lifter and keep it in place.

Another excellent reason for everyone with an S6/S8 to inspect their intakes and replace them if there are broken flaps.

#4

I did find smaller pieces of plastic on top of the valves. I’m just going to have to inspect everything good before it goes back together.

#5

Replacement clynder head came today along with the timeing tools. I’m only using the camshaft from it.
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#6

I think from what the picture shows that there is a very very good chance its from the intake manifold parts. Were you able to find the rocker and the rest of the parts in the head in the valley of the head?

If not I’d pull your oil pan to make sure you don’t have any debrits floating around in the pan. That could come back to bite you. Also why not just use the replacement head? If you pulled out the rocker on the once cylinder there isn’t anything to show if the other cylinders or rockers didn’t get or experience any slight damage as well. It might just be a good idea to swap heads.

To have damage to a rocker like that isn’t normal. Even if we do accept that all this happened from the intake parts that still leaves the question if any other part or rocker was damaged in the prosses.

You can obviously just try to swap out the top half of the heads just be careful tightening down the cam caps.

#7

Pulled the engine today. When I went to lock the crank and cams I found the exhaust cam not spinning.

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#8

More damage pics. Exhaust camshaft bolt came out by hand.
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#9

Can you see if there may have been some work done to the car previously? If so, the work may not have been properly done?

That’s the only thing I could see that would be the cause of the cam problems as I have always read that the 5.2 V10 is pretty bullet proof.

#10

I’m suspicious of that same thing. This silicone does not look factory too much of a glob in the engine

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#11

Yeah, looks like plain old regular black RTV. Who ever was in there before didn’t put things back together correctly.

Wish you luck with getting everything sorted out. Definitely inspect as much as you can while you have the engine out.

#12

Yeah across the board I would check everything pull the back covers off and check the tensioners and all of the timing components. At this point there might be a rabbit hole you don’t want to close the motor back up just yet.

Also make sure to check the oil pan to see what might be lurking in there.

The Audi RTV is black so not sure if that is aftermarket or factory but you would have to gather either way its not supposed to be there.

#13

^when I took mine apart the OEM sealant was very clean and nice. Definitely not OEM.
wondering if they did not torque the cam bolts 90 degrees.
both need to to be pretensioned (the adjuster itself) at 60 Nm, then tightened to 80 nm. then once all done and pretension is off, final torque to 90 deg.