Valve lifter problem? (Oil pressure? Journals? Oil pump?)

(Sorry for this being so long, but I'm trying to tell everything so you can try to make the whole picture of the problem)
I have a Audi A6 1996 with 2.6L V6-engine, with hydraulic valve lifters.
The car has been driven for about 85k miles (<140k km)
One and a half week ago when I started the engine, there was loud clatter, like when the valves don't work ok, but this one was _loud_, believe me.
The oil change was due in near future, so I booked time from local repairshop for oil and filter change.
I don't know what oil's there have been before, but when I bought the car, I applied Mobil 1 0W-40 synthetic oil. I've only changed the oils once, before this week.
The repairman said that the valve lifters need to be changed, as the noise was too loud for normal operation.
So the valve lifters were changed, as well as the oil and filter.
And the noise didn't go away. Under the valve lifter gasket, there was lot of ... something (not dirt, but something), so we figured out to try engine flush and new oil change, if the something had clogged oil journals (the oil channels are called journals, aren't they?) from other V-branch. Also, when the gasket was removed, and the engine started, no oil came there, just few drips from somewhere. So it seemed that the clog in some journal stopped the oil from entering the valve lifters.
The flush seemed to do the trick, but when I had driven for few miles, the clatter returned. Next day, I drove the car back. At first, the clatter was there, but when I arrived at the repair facility, the engine was quiet.
They did the engine flush again, along with the oil and filter change. This time I drove around for 20 minutes nice and slowly, and engine seemed ok. Just when I entered a freeway, the clatter returned. When I headed back to the repair, the noise went away. I drove a little with higher rpm (~3000 rpm), and the clatter returned, and when I drove more carefully, it went away. For some moment, the clatter didn't return even with higher rpm, but then with one faster acceleration, the clatter returned ok.
So it seemed when the rpm's were raised more than average, the clatter came, and when driven slowly, it went away.
So what could be the problem?
I have been given thousands of hints, but not sure which one to try first.
One is the something in the engine, which might clog the journals again and again. Several flushs might do the job, or maybe some other methods?
Can the over-pressure valve at the oil pump be defekt, so that it starts to leak always when the rpm's are raised, thus negating the oil pressure raise when accelerating? I suppose the oil pumps themselves usually don't break down with this mileage, as well as they usually tend to work better with high rpm's. The oil pressure light never lits, but can I trust it?
Something wrong with the oil filter, or the interface between the engine and the filter?
The rotating rod (shaft? cam shaft?) which moves the valve lifters, is/are ok. What else should be checked before the engine is totally torn apart?
Hopefully someone has some ideas, any good advice would be appreciated.
-Tero
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Theory time.......... sounds like debris is in the oil pan and at higher rpms, the oil pump sucks at a greater volume and the debris clogs the oil pump strainer. Then the oil pump pumps less oil to the lifters and that noise develops.
Testing time....... See if my theory is correct by installing an oil pressure gauge and observing readings while conducting the same high rpm tests.
Or drop the pan to check and possibly change the oil pump.
Are you using good oil filters? which brand?
later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris
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On Tue, 27 Apr 2004, dave wrote:

This is very possible, I just wish this could be proven fact, and also given a good solution to get rid of the debris.

This is one of the next things to try (I wonder why the repairman didn't test this at first??)

I was told that this engine needs quite much labour (=cost) to open the engine. So far, the costs have been quite nice, and almost nothing has been done, so I wouldn't want to spend any more money at guesses. I wish there was some way to make certain what is the problem.

Don't know, since the repairman has acquired them. Should be ok, but this was one of the questions which I intended asking him next time I'm visiting him.
One of the thousand quesses, was that if the filter has too small flow holes (or what you call them?), then the oil flow "chokes" when it needs to flow more. One quess, but I don't believe too much in this one.
-Tero
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Tero, Sounds like the "Orange Filter of Engine Death" to me - paper element cannot handle the high oil flow and implodes - sucking chunks of paper into the oil passageways in the engine. I've only heard of this with older 200/5000 turbo engines, but the filter that may have been the culprit was thrown out with the oil/filter/lifter change, right? Unfortunately, the people who I have heard this happen to have had to undertake a major motor rebuild to get the fluff out of the system. When the engine was flushed, did you look to see what came out in the flow? Given that the engine is so new, and the onset of the noise so instantaneous, it's a wonder why your repair guy didn't drop the pan - maybe it's time to change the repair facility before they change anything else on spec. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

sucks at

observing
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On Tue, 27 Apr 2004, Steve Sears wrote:

I wasn't around when the engine was flushed, so didn't get to see the oil. I guess that the filters aren't the cheapest around (nor the most expensive), but I suppose I will ask the repairman about the filter. They are experienced with Audis, so I assume they shouldn't have done a mistake that stupid. I really hope this isn't the case, since rebuilding the engine doesn't sound too cheap solution. In addition to stupid car tax regulations here, there is some limits how costly repairs are reasonable to do for cars that old.

Around here, there's two choices. Either the local Audi dealer, which costs like hell, or private repairs, which cost moderately cheaper, and in fact, in many cases do better job than the dealer. This one seemed to be better than average experienced with Audis, so I wish I could rely on their expertise.
Thanks for the tips Steve.
-Tero
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edited

get some oil pressure readings at different rpms and/or while that lifter noise is occuring

later, dave Reminder........ Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you are a mile away from them, and you have their shoes. Frieda Norris
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On Wed, 28 Apr 2004, dave wrote:

Just talked with the repairman, they had installed oil pressure gauge, and measured the pressure while the problem was on. I don't know what the readings were, but he said they were ok. If I talk to him again, I might ask the readings, if he did wrote them down or is able to memorize them. (Why I used _if_ instead of _when_ :) )
Next thing he suggested to try, is to open up the motor and try to find what and where the clog is.
One guy suggested, that the... isolating thing between the engine and the cover, which mostly keeps oil from spilling out, whatyoucallit?.... might be worn so, that it partially blocks the oil journal. If the engine is opened, it will be replaced the same time so it might correct the problem. (or then again, it might not...)
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Ever replaced the Belt and Belt tensioner?? I suspect your problem lies either here or in the oil pump.

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On Tue, 27 Apr 2004, JP Roberts wrote:

Not sure about the tensioner, but the belt is changed 10k miles ago (~16k km).
Can it be the pump, if the other V-brach works (or at least seems to) correctly?
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I had some noise at tilt, and some detonation under load at around 1950 rpm - on my 1.8T, and it all disappeared when I had the belt, tensioner and the V-branch pulleys replaced. Since your car has over 140 thousand km in the counter, you should already have had those replaced quite some time ago, so I'd suggest your doing this before any further attempts at replacing the pump.
Also, since it seems to be the case that the noise occurs under engine load - as you mentioned - this might indicate that there could possibly be a bad belt tooth causing detonation because of excessive timing advance at certain times when the bad belt tooth sent the wrong ignition timing. Because it's a six cyl. power loss might not be so noticeable as it would on a 4 cyl. engine.
My two cents,
JP Roberts

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On Tue, 27 Apr 2004, JP Roberts wrote:

Hmm.. given my great knowledge about English, what you mean with V-branch pulleys? When I was talking about V-branch before, I meant the other half of my V-engine. I recall 1.8T is not V, but straight.
But if the belt is changed under 16 thousand km ago, I suppose it shouldn't be problem yet?

What indicates that it is not timing nor ignition problem, is that when they removed the valve lifter gasket, no oil came there when the engine was running.
So most probably the problem is somewhere in the oil flow chain, the pump, the filter, the journals etc... or maybe not :(
Any comments or suggestions are appreciated, since the real cause is still unknown. I just personally suspect the oil flow chain.
Thanks for comments,
-Tero
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Did they change tensioner and idlers, and possibly the water pump at that time? I have had the timing belt(s) changed on my 2.5tdi V6 recently, and I believe there were about four idlers and the tensioner that were replaced at the same time, plus the water pump as a precaution. The idlers alone were about EUR 550, and the waterpump about 80, IIRC.
I doubt that this is your problem though.

Cheers, Thomas
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You drove the car 85K miles and only changed the oil once?

Um, I seriously hope that you bought this car used and have only had it a couple thousand miles. I wouldn't leave *any* oil in an engine longer than 10K miles, and I tend to change my own vehicles at 3-5K.
In any case, in response to your question, I'd be interested to know actual oil pressure as measured at various places around the engine. I dunno if you've got a sludge problem or actual engine wear, but I'd be betting on one or the other.
nate
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On Wed, 28 Apr 2004, Nate Nagel wrote:

It says:" I don't know what oil's there have been before, but when I bought the car, I applied Mobil 1 0W-40 synthetic oil."
So I guess that could be read as if I don't know what oils the previous owner(s) did use, but when I bought the car, I (almost) immediately changed the oils.

Yes, I have driven now with this car almost exactly 10k miles, with these oils 6-7k, as I said in the post, the oil change was due in near future. The Mobil 1 recommends around here something like 6-7k change interval. I also change filter every time when the oil is changed.

I try to get that information. Could someone tell what is "sludge", since my English-inHead-dictionary doesn't recognize that word, and my Webster is at work. Engine wear shouldn't be the issues, since it looks to be in good condition (AFAIK), if you don't look at the debris inside the engine.
-Tero
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Tero Patana wrote:

I think that what you are calling "debris" is what I'm thinking of as "sludge." Catchall word for that black goo and/or hard crusty stuff found inside an engine's oil system when something hasn't been right with it.
nate
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