RoninTT

I'm going to install a new belt/tensioner assembly this weekend and hope that there wasn't any valve damage (though I doubt we will be that lucky). I'm thinking we might as well pull the head anyway and check the valves but I have a few questions first:

The car is a 97 A4Q with the AEB engine.

-If some valves were already damaged, is it safe to assume that their valve seats are damaged too? I'm asking because we might just try to install the new belt/tensioner and do a compression test. I don't want to do further harm to the head though if the valve seats are ok but the valves are bent.

-Will the head bolts come out without a fight or will I need to spray some liquid wrench onto them? I doubt if the LW would get down into the threads but who knows. I don't want to snap the head off of one trying to take it out.

-After the head is off, if I find bent valves and have to get the head worked on, how should I protect the top of the block? The engine has to stay in the car and the car will be sitting under a cover, outside. Would a light coating of 75W90 gear oil be enough to prevent oxydation or should I smear a light coating of grease on the top of the block and in the exposed combustion chambers?

Any advice is appreciated!

paulroad

This is when the pistons ram the valves. BUT having a failed tensioner does not mean this happened, unless the car was running and it suddenly shut down with a bang when the tensioner failed.

You are only asking about the possible valve damage... there is also the possibility of Piston damage. Afterall what hit the valves? To be safe, pull the head and look it all over, calves, stems, seats and Pistons...

John/TSR

...do a "leakdown" test, as it may save you the trouble of removing the head. Any reasonably well-equipped repair shop should have a leakdown gauge (hell...I'm not a repair shop and I have one...). Basically, it works by applying a compressed air source to the sparkplug hole, then measuring the leakage past rings and valves. A knowledgable mechanic should be able to tell you if you've dinged a valve with this test alone.

Re: removing head bolts - the headbolts themselves aren't a problem. They come out without unnecessary banging. You have a much bigger problem in store when removing intake and exhaust manifolds. THOSE are the ones that are a bitch, and where you'll bust hardware and knuckles.

If you have to remove the head, clean up any excess antifreeze and just spray the block surface down with a protectant spray, like WD40 or Thrust. Then just cover it with some oily rags, or tape down some plastic bags. Just make sure that you clean all of the goo off before you install a new headgasket and head.

JAFO

<ul><li><a href="https://forums.audiworld.com/performance/msgs/54005.phtml">https://forums.audiworld.com/performance/msgs/54005.phtml</a</li></ul>

RoninTT

The tensioner must have failed during startup since it apparently ran fine the day before. Car idled like crap and died. My friend called me and asked me to listen over the phone to the engine while he started it. I could hear that it was running like crap but couldn't tell if there were any metal pinging sounds or not. It only idled for a few seconds and then died. We couldn't check the crank/cam timing since you pretty much have to pull the whole front end off to see the stupid crank mark.

The timing belt is COMPLETELY loose and the tensioner pulley just flops up and down when the belt is pulled on. I would like to think that no valve damage was done but I'm not that naive. My hope is that since it wasn't rev'ed past 2k RPMs after the failure, the pistons will be OK. Otherwise, he's going to be looking for a new engine. We are going to pull the head this weekend and check everything to be sure.

Strange thing is...I just changed the belt and tensioner on mine 2 weeks ago because I have 55k miles and was getting worried. Guess my friend just learned the hard way...

RoninTT

Leakdown is a good idea. Probably easier on the engine too, if there is damage.

RoninTT

the middle of the three intake valves had carbon knocked off their edges. So, I'm guessing the hydraulic lifters saved the valves. Compression test turned out over 120psi on all 4 cylinders on a stone cold engine so I know that the valves have to be seating OK. The engine purs like a kitten when idling and runs fine except for the stupid automatic tranny being low on fluid and stalling the car out when the brakes are hit hard. I guess it could also be the throttle cable needing adjusting but we didn't remove the intake manifold when we pulled the head so I doubt if that's it. I'll try to do a write up later this week and put a link to it here.

4Driver4

Take each one out of the head and spin it slowly in a drill.

RoninTT

cause major damage. They may not be perfect but it isn't worth the effort of pulling everything apart again and removing the valves unless they start causing a problem.

John/TSR

Timebomb.

If you dinged the valves, even veeeeeeeery lightly, they should be replaced. You're on the path to a sudden and catastrophic valve failure (dropped heads, etc.) that will take out the entire engine.

Just a little ray of sunshine on a Monday morning....