tanya_charbury

My tech is well-versed in engine mechanics, but he is not an Audi specialist. It's not ideal for me to abandon him and hope that he’ll figure everything out perfectly. It's better if I'm there, so that the two of us can figure things out together. Besides, I tend to be more of a book-knowledge girl whereas he is more of a hands-on guy, so the two of us working together makes for a good dynamic.

When I am absent, and he works alone, things are more likely to go wrong, and today I was absent for too long while he worked solo on the replacement of a timing belt, idler pulley and tensioning parts for a 2000 Audi C5 A6 Quattro 4.2, ART variation. My tech and I had previously done this on another near-identical Audi that I also own, and that I subseqently drove hard for the last 10K miles or so. Obviously, last time, we did the work at least fairly well, but that was six months ago and we don’t remember all the details nor, shame on me,. did I take good notes.

One of the points that the Bentley manual makes emphatically, in red bold letters inside a rectangle, is to not turn the engine counterclockwise. However, in the course of tonight’s “tell me about your day” session, I learned that my tech had indeed rotated the engine counterclockwise, using a wrench on the crank end, by one full revolution. Now what? What might have broken, and how do I check that, and what should I do to fix the damage caused?

My second question also pertains to the process of turning the engine, with a wrench on the end of the crank shaft. This time it was being turned clockwise only, while I listened. The new belt was already on. Even though the tension wasn’t as yet perfect everywhere, it was close enough to perfect that I don’t think there was a high risk of slipping a tooth in the belt. While slowly being rotated, the engine sounded nice, with compression quietly building and being released. No sounds of valves impacting pistons … but then there was a sudden, disconcerting sound. While the engine was slowly being rotated, from the top of the engine, there was a sudden, very loud clacking sound, like someone snapping their fingers. The sound quality suggested it was very close to the top of the valve covers, and in one of the two banks of the engine. It sounded like a spring had built up pressure and was snapping back. Then, after another half revolution or full revolution (I don’t recall) I heard that same loud sound, this time coming from the other bank. As the engine was slowly rotated, these clacking sounds continued at regular intervals, consistently. If it sounds that loud at so slow a speed, it worries me how it’ll be at a faster speed, and what that implies as to parts breaking, or already having broken.

Could it be the cam shaft adjusters, and would that sound go away once oil pressure builds? If it’s more serious, and I should do something to fix it before trying to fire up the engine, please let me know.

Thank you!

tanya_charbury

Here's an update, a day later. After a timing belt swap (or on other cars, a valve adjustment) I like to start things gently:

Step 1 is to just bump the engine over with the starter and listen if there's anything horribly wrong. If not, on to the next step.

Step 2 is to turn the engine over with the ignition disabled (in the case of this Audi, with the engine speed sensor removed) several revolutions, and listen if there's anything horribly wrong. If not, on to the next step.

Step 3 is to enable the ignition and listen how the engine starts and runs, before connecting everything up again.

So far, success on steps 1 and 2. Step 3 is scheduled for tomorrow.

Key point: during step 2, the clacking subsided and after 7 or so revolutions, presumably thanks to oil pressure having built, the noise was gone even while the engine was turning over. Yay!

So far, so good.

~Tanya

4Driver4

I don't think you have anything to worry about. The main reason for not turning the engine backwards is to avoid having the belt just. If it didn't jump, you're good. The clacking is, as you surmise, the chain adjusters getting tossed around a bit by the value springs...as is common when the is no oil pressure.

Fire it up.

Harleyguy

Have a beer(or beverage of your choice) and get some sleep. Those two things alone cure the blues in most cases. Hit step#3 tomorrow. I think you've got this!

tanya_charbury

Thank you for the reassurance. I plan to proceed, then. Thank you! :-)

MP4.2+6.0

Just visiting...after years away...but from doing belt on 2000 ART motor for various reasons at threee points in time when i owned one for a dozen years, nothing in here sounds particularly ominous. I have also turned the motor in the reverse direction and nothing dramatic happened either. I think that is a likely guideline because of the way/direction in which the various tensioners apply force.

Motor also can make some pretty dramatic noise in opening seconds after start up following extended work. I think it is vartiously the hydraulic lifters pumping up, cam tensioner tightening, etc.

tanya_charbury

Welcome back! :-) And thank you for the reassurance.

tanya_charbury

Thank you for all the encouragement. The engine starts and runs, and just as hoped, the noise quieted down. Yay!!

Three more similar cars to go. I figure it's more efficient to do them all in batch mode ... thinks my information technology and accounting girl brain.

ocles_inc

The car on which the work was done (the silver one) made a fast trip from east of Reno, NV to Monterey, CA and ran around there for a week, including an impressively quick (how quick? 5th amendment quick) blast up a hilly pass. It ran fine, yay! 2000 miles.

That's my black daily driver, next to it, equally reliable. Life is good.

Thank you for all the guidance and encouragement! :-)

~Tanya

Harleyguy

Looks like blackie could use a headlight lens treatment. I like the Mothers brand. Easy to use, not too pricey, and great results. :-)