Without going into the whole story behind it, I find myself trying to figure out the damage done to my 2.8L 12V ('96 A4 Quattro).

Here is my plan to diagnose, please correct where needed.

#1: Use compression tester and check each cylinder one at a time to see what PSI is there. Looking for around 180, anything lower than (what? 100?) means bent valves. TB is gone, so I plan to rotate by hand (tools) the cam gears and check each cylinder. **Question - Where should I position the engine crank? Is there a position that will allow me to check all cylinders without interference?**

#2: Seeing as it happened at 65-70 MPH I am assuming bent valves. I plan to get some salvage heads and replace after checking the piston tops. I did not hear any loud noises or other indications of major damage, so hopefully they are ok.

#3: Remove, replace heads, gaskets, etc. **Is there anything else I should do or check while I am at this stage?** (Not just TB related)

#4: Replace TB, waterpump and oil seals. Manually turn engine over to check for correct timing.

#5: Button everything back up. Pray for success.

Any recommendations on head gaskets? Can I get a thinner gasket for a little higher CR? Engine has 106K on it, so...

 

You bent most likely every valve. Sucks but thats the truth. Pick up a partout set of heads, check the pistons, maybe just go all out and rebuild the motor if your mechanically inclined.

 

Yeah, I'm assuming the worst. Should I even bother wasting time with a compression test?

 

It wouldn't hurt, but I don't see how you could. Ive only heard of ONE time a belt snapped and valves weren't bent, it was on a 1.8t that was idiling at a light

 

at least you've only got 12 valves, way less complicated than 30! good luck!

 

They should be all toast, but did you try and start the car after it died? Cuz then they are def all toast.

 

Well, I bought a "beater" to drive so I could take my time and fix this right. So far it's been more about taking my time.
Regardless, I dug far enough into it today and found out that my belt did NOT break. It appears that the pulleys are toast as evidenced by the bearings I found under the crank pulley. The belt shows signs of severe rubbing/chaffing on the back side, due to one or both of the pulleys seizing up.





What is the best way to check and ensure the timing is still "on"?

I have a Bentley on CD-ROM, but I haven't checked their procedure yet.

 

Your timing definitely isn't going to be "On" but the way you want to check is by pulling the valve covers and looking at the timing marks on the camshafts. I would NOT even crank it over by hand at this point. Get a belt kit and install it and then start messing with it. It's just not worth the risk. Also, even if you did crank it over by hand you would not get and accurate compression test reading. If I were you I would be happy if you had any compression at all. Also, how were you alerted to the problem? Did the engine die or did you hear bad noises and shut it off? Were you driving the car, idling, or just starting it?

 

I was driving and yes the engine died. I did not hear any bad noises during the shut-down. While it was idling an hour or so previous to this, I could hear a rattle from the timing belt area. I opened the timing cover to check the belt tension and it was "loose". (This was the driver's side cover) I figured the tensioner was going out (I was new to the Audi engines at the time) and it was Sunday in rural Illinois, so I continued to drive it.

I realize that this is usually what causes the timing belt to break on people. The idler or tensioner wear out and smoke the belt. So yes I am extremely lucky I guess.

So in order for the timing to be off, the belt would have skipped some teeth, correct? Also I thought that the 12V V6 does not have any cam timing marks. I guess I am wondering how the cams "know" where they are. Do the valve springs force all valves closed, positioning the cam where it should be relative to TDC? I have read that the cam sprockets are to be aligned with the proper tool and then pulled off (not completely unless replacing cam seals). Does this allow the cam to be positioned perfectly for the reasons I stated above?

 

There might not be any marks on the cams of the 12v but yes the little wings on the pulley need to line up (big holes on the inside.) Since you were driving I think the prognosis isn't going to be very good. Look for a deal on a set of heads ASAP.