Will I be in the Hall Of Shame tomorrow? (long post)

firefly08

...with bent valves :eek:

The suspense is killing me so I thought I'd get it out of my system here.

I am changing the timing belt on my Audi A6 2.8 V6, and I decided to take the opportunity to pull the camshafts to replace leaking oil seals. I only had to do this on the passenger side, on the driver's side there's enough access to replace the seals with the cams in place (US model).

But when I put them back in, things took a turn for the worse...as I tightened down the bearing caps, the camshafts went a bit out of alignment. "No worries" said I, "I'll rotate them back when I'm finished". But before I'd finished installing the caps, the cams had moved even further. Not quite 90 degrees off, but definitely more than 45 anyway, clockwise. So I turned them back...then afterwards realized that I may have bent some valves! :eek::eek:

I don't know why I didn't cop it at the time and remove the cams and start again. They would have sat more easily when turned a little off anti-clockwise, which I think would have been fine, but because I insisted in trying to install them with perfect orientation, they turned the other way, which I suspect is bad. I had the bearing caps tightened down more than half way before I rotated them back.

I didn't feel huge resistance when I rotated them, in fact I used a small vice grips on the unfinished camshaft surface so I didn't have much torque. A lot of people say you couldn't bend valves this way. On the other hand, the crank was locked. So if there was valve/piston contact, something had to give. Maybe I damaged them when bolting down the bearing caps, although I didn't bolt them fully down. Again I didn't feel much resistance as I tightned them down...it felt like the resistance of the springs, but who knows? I still had a ton of work to do after this, so with a heavy heart I finished it all and started reassembly. Today I'll get the new timing belt on and all the aux belt junk and finally start it up. Fingers crossed.

Imagine the irony if I damaged the valves myself doing a timing belt change

Nissan doctor

If the cams rotated while tightening the cam caps, then they would have naturally rotated to a position of least resistance, .i.e, they wouldn't have been pushing down on the valve's.
If you had tightened them down fully, then you could have been in bother but if the caps weren't fully tightened then its very unlikely that you will have done any damage, especially since you say there was little or no resistance to moving the cams.

Its normal for the cams to move when tightening but once they don't rotate to the point where they are opening the valves of the cylinder which is at TDC when there should be no contact.

firefly08

Thanks. That's pretty much what I was hopping.

Well I fired it up just there a few hours ago anyway. It started straight away, no hesitation. At first there was a nasty rattling sound, but before I had time to panic it disappeared, and the engine idled perfectly. I am fairly sure that the noise was the hydraulic cam adjuster getting it's pressure back, I've been told they make funny noises brielfy after you've had them compressed.

Anyway there was no sign of misfiring which is what I presumed I'd be seeing if I had clobbered some valves? It sounded perfectly normal. I haven't got to drive it yet because I'm still not finished putting the front end back together.

firefly08

...and it's as smooth as honey. 190,000 miles, and it still drives perfectly Now to wait and see if my oil leaks are gone.

I did get a noticeable smell, kind of reminds me of epoxy or something, and there was a faint little bit of smoke from the rear of the valve covers when I was letting it idle up to temperature, but given where it was coming from, and the way it smells...and that the car is running fine, I'm pretty sure that it's excess gasket sealant. Hopefully it won't last much longer.