WhyNot4Rings

My 30V 2.8 with 109K bent the center intake valve on the number 3 cylinder which also mangled the spark plug. Did the timing belt at 80K, and everything there looks fine.

I'm in the process of pulling the head. Any ideas what could have failed? I'm guessing the valve spring?
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Just Me

spring? Variable valve timing? Tensioner? Jump some teeth? Suck in a marble?

Certainly not common.

G

Zaphodb17

With the mangled spark plug, I'd say you have a foreign object in the cylinder, unless, of course, the valve head broke off...that'll certainly play havoc. But G is right, certainly not common. You didn't have bad detonation and have a piston come apart did you? Again, not something I'd expect on these cars.

SloopJohnB@mac.com

If it's a valve spring you'll find out. If nothing else is wrong you sucked in a foreign object is my guess.

Airbag

didn't quite get this one .. how do you know if the valve is bent if your still in the process of taking the head off ? Once you get the valve cover off you will know if it is a busted spring .

WhyNot4Rings

Looking down the intake port after removing the intake manifold you can see that the center intake valve is bent in the guide. Also looking through the spark plug hole you can see the valve hanging down there, and when you manually turn the crank, you can feel the valve touching the piston.

The UPS dude just delivered the polydrive socket I bought from ECS, so I plan on getting the head off tomorrow.

Airbag

Ah Thanks for the explanation .

Do you have a manual gearbox ? If the timeing belt and timing is in fact fine and you bent a valve the other thing that can cause bent valves is a mechanical overrev ... quite often termed as the "money shift" basically if you missed a gear and went into second instead of fourth. You would have valve float and the piston would whack the valve as the spring can't pull it back .

Not sure if the Automatic transmision is capabe of that as it is electronically controlled but does give you another avenue to explore.

SloopJohnB@mac.com

Yup...visible hanging valve indeed indicates broken valve spring.

Hey...inspect the spring closely and look for classic 45degree helix fracture coupled with fracture initiation point at the outside of the spring coil wire. Perhaps Audi had a bad batch øf valve spring materials/springs? A nicked spring wire can fracture after several million cycles.

Of course, if it's 10 years old and 250K miles you've certainly got a lot out of it.

WhyNot4Rings

Looks like the worst possible outcome - the motor is toast!

<a href="http://s834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/?action=view&current=IMG_1391.jpg" target="_blank"><img src="http://i834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/IMG_1391.jpg" border="0" alt="Somethings missing..."></a>

<a href="http://s834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/?action=view&current=IMG_1393.jpg" target="_blank"><img src="http://i834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/IMG_1393.jpg" border="0" alt="What's wrong with this pic?"></a>

<a href="http://s834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/?action=view&current=IMG_1392.jpg" target="_blank"><img src="http://i834.photobucket.com/albums/zz261/eddieonline/A6%20Avant/IMG_1392.jpg" border="0" alt="Exhaust Valve Imbedded"></a>

Airbag

oh mY !!!!!