Broken exhaust cam adjuster pin

[mattg1.8]

Looking for some help and to validate my thought process on my most recent pickup, 2007 a4 2.0t. Previous owner said “a camshaft bolt backed out” and said it made some bad noises and he shut it off. He pulled off the valve cover, hpfp, and cam chain cover then left it alone. I looked at it today and notice that the head of the bolt that holds the cam chain adjuster sprocket to the exhaust cam broke and the pin that aligns with the cam sheared off. The timing belt is still in tact and timed to the crank. So my thinking is, there should be no valve damage- the cam adjuster sheared which essentially de-linked the intake cam preventing it from opening valves and the exhaust valves continued to open in time with the crank. If my thoughts are correct, I should be able to get a new cam adjuster and reassemble right? Only other minor damage I noticed is a slight divet in the exhaust cam alignment notch that the adjuster pin sits in. Does it look bad enough to have to replace? I guess the real question is why would this thing shear in the first place? Any help is appreciated. Some pics taken in a small circular mirror, you can see the bolt still stuck in the cam.

[mattg1.8]

[mattg1.8]

[mattg1.8]

[mattg1.8]

[Gowking]

It will be sheer luck if there are no bent valves. Think about it, if the cams became uncoupled and the intake cam stopped rotating there had to be some valves left open while the pistons are still moving up and down.

[mattg1.8]

Good point I didn’t think of that. Leak down test should be able to tell if there’s bent valves right?

[Jayz691]

Yeah, as mentioned, you'll be good on the exhaust side, but intake side is still susseptable to damage. Same if chain breaks, exhaust stays in time, but intake can still get damaged.
Now to why it happened, thats the question. Nomally when something breaks like that, its from a cam locking up. Like from oil starvation, etc.
Have you checked to see if both cams still turn fairly easy?

Sent from my LM-G710VM using Audizine Forum mobile app

[Gowking]

I would pull the cam girdle and inspect the journals. If they are good then do a leak down test. If they are scored up then the head is probably trash and you have bigger issues to sort out. There’s a reason the bolt and dowel pin are sheared off.

[mattg1.8]

Just to close this thread out, the head is completely smoked. Looks like the top end was getting no oil, destroyed the journals on the head, scored up the cams and girdle which likely caused the cams to lock up and shear the cam adjuster pin and bolt. Also bent both intake valves on cylinder 1. Picked up a used engine and gonna toss that in there. Thanks for the input.

[Gowking]

Be sure to replace all the typical wear parts with quality VW/VW OEM especially the stuff at the back of the engine. Better to do it before dropping the engine in.