MeanGene4.2

A6 4.2 sounds like it's rattling knives and forks when I turn it over. Sounds smooth again right away and runs fine, but it's a scary sound. Oil level fine, recently changed by dealer, along with T-Belt and company. Car has 102,000. It's cold, but the car never complained before. Any thoughts??

SloopJohnB@mac.com

check oil level. Might be low. Mine rattled once when it was filling up the oil filter. Didn't rattle anymore.

old96A4

MIne rattles too. I have to 3.0, its sounds like its a second for the oil to travel through the engine then its fine. I don;t like it either. I put some STP in to make the oil more stickey so it stay on the parts, when its cold its not so bad but in the summer it doesn;t sound good for s second after starting. I hope its not hurting anything or the engine won't last doing that for very long. I have 74K on mine so far.

johnkk

the 4.2 in my Touareg rattled at start and this is attributed to dry valve train after overnight rest. My 2.7 A6 is quiet.

I just changed the Treg oil for the first time myself and put in the Mobil 1 0w-40 that I use in the Audi, and the start up noise in the 4.2 is much less, even on 10degreeF mornings. The local dealer uses Castrol 5w-40. Hard to believe that the oil could make the difference, but maybe?

jschick

the oils can make a big difference in noise. on all the Audi and Saabs I have owned which both are known for sludging, I typically run some seafoam in the oil for about 300 miles then change the oil. When I bought this 98 A6 the oil was very black and it made all kinds of noise, after seafoam and new oil i can't believe how much it cleaned it up, even now after 1500 miles since oil change the oil is still pretty clean, and no rattle on start up. just this past weekend I finally got around to Seafoaming the intake as well, no more check engine light and it runs great (I was getting Lean cyl codes 17544 and 17546 which typically points to Vac leaks)but after Seafoam it hasn't come back yet after 200 miles! it had been comming on every 5-20 miles after I cleared it.

cvanc

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old96A4

So if you get the chatter is the oil to thick or to thin?? to thin would make it run down to the pan I woud think. To thick would take a minute to circulate. Maybe I'm using to thick of oil, Castrol 10W40 I think the last time I did it?? 3.0 engine.. maybe should use 5W30. will it hurt the life of your engine after a while???

jschick

I am running 10w40 castrol, the Seafoam is a all purpose cleaner, It is really the only stuff I have used that actually does something, you can find many posts on how to use it to clean the intake (sensors and vac lines), it also can be used by dumping it directly into the oil which breaks up any deposits, I think the oil channels running to my chain tensioners and lifters were dirty, My car has 130k on it and I had some lifter clatter and very noticable chain tensioner clatter at every startup. after I used it, my lifters make no noise at all and I only get a real faint rattle or whirl from the cam chain which only last a few seconds (3-5 seconds)on a very cold start (below 20 degrees)normally I don't hear it at all. normally I put it in and drive about 100 miles but i got tied up and didn't get it changed for almost 500 miles, the oil was so black I couldn't believe it.

gtrucinski

Guys:
These are classic signs of timing chain tensioner leakage. The timing chain is dragging over the chain guides. BUT I assume he has a 2000-2001 A6 4.2??? This motor has a timing belt so it must be leaky or sticky lifters. SEAFOAM (NAPA) is a great idea to test the fix. If that doesnt work you will need to pull the cams and replace the worn out lifter or lifters (One per valve).
I have a 2004 Alroad 4.2 and had the same symptoms because I have a rear mounted timing chain on this particular motor. Dont think they used this motor on other models but??? I pulled the trans and replaced the tensioners to fix the problem.

Just Me

yes, that's true ..... but In 25 years of audi ownership i have always had lifter noise. yea, it gets worse as oil change time approaches. Yea, its worse when the car has sat, yea........ but its been a constant, like Pi, G or the tax rate.

And, at lest one of those cars clattered happily away, with no ill effects, for > 300k miles. Admittedly it was an I-5.

So dont spend too many cycles worrying.

G