Re: Clicking valves again... and synthetics

[steveb@falcon.kla.com (Steven Buchholz)]

> His advice was to switch back to non-synthetic oil.  He says that the 
> synthetics do not work properly and that Audi discourages their use.  Is 
> there any truth to this?  ANybody heard the same thing?  Does a clicking 
> valve equal lost power? more wear? or both?
> 
I've never heard anyone switching from synth ... but I don't have that much
personal experience with synth in a hydraulic lifter app.  After I fix that
leaking crank seal on the 5k I plan to do the switch.  My experience with 
the 5000 is that the lifters seem to be the quietest after an oil change, 
and they get worse over time until I can tell that 3000 miles have passed
because the lifters never quiet down.  There also seems to be some correl-
ation between oil level and the amount of noise ...

There are several Audi service bulletins on noisy lifters, one talks about 
replacing the oil return valve in the side of the engine block.  It was a
cheap test, so I tried it ... didn't help.  The only thing that worked on
the 5k was a can of oil additive that was meant to clean lifters.  That 
stuff quieted the lifters almost immediately and it lasted for a while ...
but now we're back to the old MO ...

I don't claim to be a True Expert (tm), but here's my take on noisy lifters
... the lifter makes noise because the lifter loses contact with either the 
cam or the valve stem, and when the cam starts the compression operation 
this gap is closed and a tapping noise occurs.  The lifter is meant to cush-
ion this encounter by staying in contact at all times, but still allowing 
for some of the lift to be dissipated by fluid leaking from the lifter.  
IMHO, as long as the valve lift is the same and the valve timing doesn't 
change significantly then the fact that the lifters are noisy isn't much 
more than an annoyance ... I actually suspect the truth to be that when the 
lifter is making noise that either the timing or the max lift *IS* affected 
... meaning that you may very well be losing power.  

My other concern about noisy lifters has to do with knock detection.  I have
a friend that owns a VW GTI.  He was complaining about how his motor seemed 
to be down on power ... big time.  He mentioned in passing that he had re-
moved the A/C compressor belt because the mounting bracket was broken and it 
was actually swinging freely and could hit the engine block.  I suspected 
that the engine was interpreting this as knock and retarding the timing.  He 
removed the A/C compressor and his engine returned to its former performance 
level.  

I'll post this response to the list as well so that if I am totally misin-
formed on this we can have that pointed out before I pass that misinforma-
tion on to you!

Good luck Steve!
Steve Buchholz
s_buchho@kla.com
San Jose, CA (USA)