Audi A4 1.8 automatic, awd, turbo, 2001, about 150K miles, started getting a knocking in what I am pretty sure is a cam chain tensioner. It is okay when cold starting, or at higher revs, but it starts knocking or tapping when it gets warmed up. It just started happening now that the weather has gotten warmer but could be coincidence. Did some searching and got a lot of good info. thanks to all the posters.

Wondering if my cam chain tensioner is faulty or if my oil pressure is too low. It idles when hot at about 16PSI, but about 25 when cold, and will also go up that high with a slight tap on throttle. Tapping from cam tensioner starts when pressure drops to about 17.

I rigged up a simple oil pressure gauge. It was about 12 bucks for the manual gauge, and 8 bucks for the hose and fittings, all from Oreilly and fit together perfectly, by the way.

gauge first showed a pressure of about 25 psi at cold idle, and went up to about 80 at 6k or so revs, a bit less at medium range. I ran it for about ten minutes and it dropped down to about 20PSI at warm idle. No knocking. But i had to go.

Today, drove it for a few erendes. In anticipation of an oil change, I put a can of seafoam in it. Don't know if that thinned the oil a little. Once it got good and hot (the outside temp is about 65) the pressure at idle drops to about 15 when idling 40 or so at low reves when cruising, and with acceleration will still go up to 75 or so at high revs. Once it drops to about 17 PSI, it will start tapping. A slight throttle increase, taking the revs up a little over 1000 will stop the noise when it brings the pressure up to about 18 or above.

Oil is probably going on eight thousand or so miles, mobiltech 5-30 synthetic.

When I bought the car, I got it through my friend who manages the used car dealership and specializes in Audis a lot. After driving about 20K, it started getting a knocking sound and red oil can came on. stopped and towed it to the used dealership my friend worked at. Together, we dropped the pan, replaced the oil pump, cleaned screen and pick up, used the new modified pump etc. Looked okay, not too sludgey, but we cleaned out the pan and such.

Now it is about 20k more miles. I recently replaced valve cover gasket, and the one under the cam chain tensioner. It knocked for an hour or so, when I put it back together then stopped. It has been fine for maybe 3K miles. But then started knocking.

So, the questions I have is, what is the normal pressure range for an older audi that is running well and within spec range? At idle? At high revs?

Is it normal for a functioning cam tensioner to start knocking at this low a pressure?

Is my pressure faulty, or my tensioner, or both?

Is it possible that some fresh oil and bumping up to 5-40 will raise the pressure enough to solve the problem? Or would I also need to replace the tensioner?

Is there anything else simple I could do to improve the pressure, or is it an indication of serious problem such as worn bearings, etc?

Any help is greatly appreciated. Sorry to write so much but I figure more info is better than not enough.

 

Drove it again just now and notice that when first starting hot aor turning off, it will tap a little as the idle drops, so I am assuming the tensioner is bad now because it didn't seem to do that before? Agree? Also, wondering if I am doing damage to my car with every tap or if this is not too bad for now, and will only be a problem if it gets worse. Not going to jut ignore, but would like to be able to keep driving the car if it is not creating damage, till I can order parts and make the time to change. But if this is doing damage, I can park it and drive my beater back up. thoughts?

 

Well, replaced the oil with 5-40. It idles hot at about 24 lbs oil pressure, but it is about 60 degrees. Will see what happens when it gets to 80 degrees. No tapping or knocking. Actually, I do hear a slight knock like a diesel, but my car has sounded like that for the last year. It is either normal or very slight. I guess i will drive it and keep an eye on the pressure, and if it starts dropping lower, i will have to figure out what to do, but if it stays the same and the tensioner starts ticking loudly at current pressure, I will just replace it. My guess is I was right at the juncture of slightly low pressure and slightly worn tensioner, which resulted in tapping. Hope it holds out a while because the tensionr is $450.

 

Hey Blue,
My girlfriend has the same car. We were driving up a long hot interstate on a very hot day and her alert bell went off. Her diagnosis LCD was out however so we couldn't tell what the actual problem was. Shortly after the knocking came in and after about 10 miles of pretty loud knocking we found a gas station and pulled over and eventually got it towed to a local shop

Pretty much the same symptoms you noticed. You seem to know a bit about cars, I know less but this info may be helpful for you:

Turned out the oil pressure was very low (we didn't measure it but the fact that no oil was getting up in the top of the engine head)
The first mechanic heard two noises, a loud knocking up top and a low rumbling in the engine bowels.
He said the engine was shot and we needed to get it replaced or the car may explode.

we decided instead to get it towed up to her local shop who are specialists.

They assured us that it was just the oil pump and the tensioner and that replacing both of these would fix the problem.
They did and the loud noise up top stopped but the rumbling was still there so they said, 'oh no problem we'll replace one of the barrels and that'll fix it.'
it didn't, it turned out to be damage to the crank shaft and cam,
the engine is done
the first mechanic was right it turns out.

Again I am not an expert but it sounds like the engine damage came from driving too long with the low pressure and the tensioner shot. I don't know when the problem actually started but apparently audi sent out a bulletin describing this problem as a common one, apparently they were even fixing cars with this problem but I am sure that was a limited time offer. I've been trying to find more on this bulletin but with no luck.
anyway it may be worth it to do the tensioner
I wish I had more details for you, but I hope this anecdote was helpful

 

Anytime a gasoline engine makes noises resembling a diesel engine, it has problems with either the rod bearings or the main bearings.