Before you start ripping your engine apart, have your mech check all the belts. My 2000 A6 4.2 sounded diesel-like for quite some time on cold start and warmup, and then after driving it for about 30 min, the noise would fade. I was about 10K miles overdue for serpentine belt change, and when they did it (about $275), the noise went away. The timing belt's another story. $3000 or a long weekend DIY and hopefully good weather. Check your belts.

 

Sheesh... talk about confusing someone!

V6 SOHC = 1 cam per head = 2 cams per engine

From what I know...

'95 V6 12v has a Timing Belt

There are 2 Tension Idlers - 1 is adjustable

'Diesel sound' is usually meant as 'clacking' while at idle, or 'pinging' while under load... if your getting a 'clacking' sound at first, cold, startup, then its usually the lifters/cam followers as they lose oil while sitting. Your having it sit for 2 weeks or more contributes to this greatly. You should check those 'oil valves (anti-drain back valve)' you mentioned earlier as they keep the oil in the top of the engine to help 'dry starts' like this. The other 'anti-drain back' valve is built into the oil filter. As mentioned, some filters are better than others in this regards - I personally use Purolater Pure One specifically for this reason.

The other reasons for noise at startup are bad idler bearings, loose/worn belts, loose heat shields, worn internal components (rod/main bearings, rings, etc).

When you change out you TB, you will eliminate many of the belt/idler causes.


If you haven't seen this before, you should:
http://forums.audiworld.com/showthread.php?p=18573824


Blauparts has everything you need.

 

Yeah, the belts may be a problem, although the "diesel-like" noise comes from the top middle of the engine. Maybe it is just a misplaced sound, but I could swear that if I lean right over the top of the intake manifold I can hear it right "there". However, with the two engine headers on the side of each ear, it could be like a "stereo effect" sound you hear "in the middle"...

I know that the TB needs to be replaced, that's why I haven't moved the car in about a month. I presently have 153,000 miles.
It has been done at 85600, some +6 yrs back, so it really needs a new one as, beside the diesel-like noise, I can hear rattling against the plastic covers. I should get the locking/holding tools by Monday, if UPS' schedule is correct.

The drive belt was replaced about 2 yrs and some 18,000 miles back. I doubt that one constitutes a problem, but you never know. Maybe the tensioner started acting. I have a new one to replace it anyway, as I will get into the TB job.

As far as ripping the engine apart, I'll hold my horses in the stable until I do the TB job.

Thanks for chiming in.

 

You posted while I was typing. Well, I got over the confusion rather fast with a little bit of common sense.. Sometimes (some) people have hard time explaining things. I know I do, so I didn't consider that nemohm wanted to confuse me. He just didn't explain it in a way that I should have been able to understand it.
Anyway:

That's exactly the information I was looking for. For me, it isn't quite easy to talk about something that I have never seen or experienced prior.

I appreciate the information. Thanks much.