I just bought a 2001 A6 Wagon 2.8 off a guy for $350. The guy bottomed it out and busted the oil pan. Drove it home and parked it. Had it towed to a shop and had the pan replaced. It was running "rough". The mechanic couldn't figure it out. Mind you he was a "normal" mechanic with no euro experience. So the guy takes it and drives it for a few days. Day three it dies at a red light and won't start back up. He pushes it into a parking spot and puts it on craigslist.

So I pull the bumper and remove the radiator housing to access the front of the motor. It will not turn over when you try to start it but you can manually turn it over from the crank pulley. When you do turn it over it makes a loud click then another loud click then it locks up. Same thing when you turn it the other way.

I take off the passenger side valve cover to get a look. When it turns over there is an arm that pushes on, what I suppose is, the timing chain, in the back of the motor. It will go up when you turn it over and then slam back down and make the click noise that I was hearing. It will do that a couple of times and then lock up. The same in the other direction.

My spidey sense tells me that that is some sort of safety locking mechanism that is engaging. I may well be wrong but I am throwing this out there for any one who has some experience and/or knowledge in such things and would be so gracious as to share with me. Thank you in advance.

 

Busted the oil pan and drove it home? Just how "busted" was it? There's your problem right there..

 

I gave as many details as I know about the situation. I'm aware that driving with a busted oil pan is the source of the problem. I'm just curious as to whether or not there is some sort of safety feature that locks the motor up at a certain point if something's not working right or if I need to be ready to tear the motor down to find some broken piece

 

No safety feature will lock the motor up. Oil pressure failure will. The "arm" that you are referring to that interacts with the cam timing chains is a tensioner. This tensioner also helps vary the cam timing under normal running conditions. However, if the oil pressure is low or the engine has been run with no oil pressure for any more than 10 seconds, you are going to have some potential seizing issues. Especially on the top end where the cams ride in head. There are no bearings for the cams. Any oil starvation is going to cause scoring in the soft aluminum that is machined for the cams and tappets. However, if very little oil was lost and the engine was never without oil pressure, it could just be the tensionser. They can be replaced. They can cause a rough running condition. A failed tensioner can also cause valve damage. I'd check the the compression on each cylinder before doing any major work. A dead cylinder will probably mean a bent valve in this case. Replacing the tensioner will require pulling the timing belt and cams. Inspect the cam "bearing" surfaces in the head for scoring. Any scoring will mean oil pressure was lost at some point. Not good.

 

There are two tensioners.. One at the back of the head on the passenger side. One on the front of the drivers side. Most of the time the plastic pads wear out. Or they leak oil and won't hold proper pressure. The pads can be replaced at a good price. Blauparts sells kits for this with gaskets and the tool to compress the tensioner. Of course you'll need to get a crank lock and cam lock bar ($50-100 on ebay for both) to keep the engine in time while replacing them. If the tensioner had failed, they are a bit more expensive...... Do NOT get them at the stealer....er...dealer.. Save yourself a boatload by getting them from another source.. Same item, WAY less expensive pretty box...

 

So the tensioner lifts up and then slams back down. Does that indicate anything in particular?

 

Correction it goes down and shoots back up. I probably should have noticed this earlier but only one of the cams spins. the other sits still and when tension is put on the chain it pops back up and lets the chain jump off the sprocket. I am inclined to believe that is not good.

 

Nope.. not good at all.. Definitely bent valves. I bet the PO ran the engine with no oil in it for too long. Some people are just clueless that way. Still for $350 you got a decent deal. However, you'll need to start looking for another engine. Rebuilding that one probably isn't going to be cost effective as it's probably damaged the cam carrier parts in the head. No bearings there to replace and re-machining isn't possible. I'd pull the cams and look to verify. I bet they and the head are scored where they ride in the head. Get the three digit/letter engine code from the sticker located in the spare tire well. You might can find a good used engine to swap out. Getting one of the same code will be basically a drop fit.

 

So I pulled the cams off the passenger side and I don't see any scoring.The tensioner has some deep grooves on the feet that touch the chain but the cams look ok. By scoring you mean that there would be marks in the metal from the unlubricated contact right? If not please define scoring.

 

p.s. there was no plastic left on the tensioner.