When I start the engine cold after sitting 4 hours or more, I get a tap/knock from the engine and squeal from the turbocharger for about 20 seconds. It goes away after the oil comes up to full pressure. It just started one day last week with no warning. It only does it after the engine has been off for 4 hours or more, so I'm guessing it takes that long for the oil galleries to drain back to the pan. I changed the oil filter (I use German made Mahle filters--the big size), cuz I figured the anti-flowback valve malfunctioned...but of course, a new filter didn't change anything. The oil pressure warning light does not come on and the oil level is at the top of the mark on the dipstick. There is no check engine light either.

Here's the info on the car: 2000 A4 1.8T Quattro 5 spd with 107,000 miles. I use Mobil-1 10W-30 oil every 5,000 miles. The current oil has 2,800 miles on it. I bought the car a year ago with 90k miles from a Kawasaki jet ski mechanic who took excellent care of the car. I don't run the car hard (typically cruise at 70 mph) and my driving is an even mix of city/highway. I typically average 30 mpg on a tank of gas.

I did some research on this forum and obviously sludge is a possible issue. I also wonder if there is some sort of check valve in the engine lubrication system that prevents oil from draining back into the pan and that check valve isn't working. Maybe a bad oil pump? This is my first Audi (love this car) after owning 3 VWs (all 4 cylinder) that never had an issue like this.

Opinions please? Thanks!

Larry in PA

 

I use Mobil-1 10W-30 that's the reason you need 0W/30 full synthetic or the least 0W/40

 

FINALLY! Problem solved! And you won't believe what the problem was...

Okay, I put in Auto-Rx 1,800 miles ago and drove for the recommended 1,500 miles and changed the oil and filter. The oil that came out of the engine was dirty but not THAT dirty (after 4,000 miles and it was Mobil-1). I always figured the noises were oil pressure related, but I NEVER got a low oil pressure warning.

Anyway, last weekend I cranked the car up cold and the usual noise was there...a squeal that sounded like fingernails on a chalkboard and an engine knock that varied with engine speed (sounded like a K-car with a bad cam). This time, I figured "screw it", I'll let it idle to see how long the noise continues. After 2 minutes, both noises stopped. The knocking ended abruptly and the squeal stopped slowly, like someone turned off a vacuum cleaner. I thought to myself, "that's weird, if it was turbo squeal the pitch should go faster as the turbo spins faster, not slower". So I pulled out the secondary air injection pump (behind and below the right headlight), popped off the end cover and put 2 drops of oil on the motor shaft. Then I fixed the crack in the black plastic accordian hose coming out of the pump and put everything back together. I thought, this is stupid; it can't be this simple. Cranked up the engine...cold, 2 hours later.

DAMN!!! NO NOISE! No squeal, no knock! WTF!?! All I can figure is the pump wasn't making full pressure (due to dry bearing and squealing), so exhaust pressure was slamming the secondary air injection valve shut (and might sound like a bad cam).

Anyway, problem solved. The car never had an oil pressure problem. At least now, the inside of the engine is clean thanks to Auto-Rx.

--Larry in PA

 

you're still using the wrong oil

 

try 5w-30 instead of 10w-30

 

the oil isnt making it into the valves until it gets warm enought to make it in trust us change the oil and youll be better

 

The secondary air pump squealing is a common problem, oiling the bearing will usually fix it if you can get it apart, however the knocking has absolutely nothing to do with the secondary air pump.
When you get a knocking or ticking type noise on cold start and it goes away after a few minutes it usually your hydraulic cam adjuster starving for oil, the oil treatment you put in it might have cleaned out the clogged up lines to the cam adjuster but it will probably come back.

 

Auditech79 said: "The secondary air pump squealing is a common problem, oiling the bearing will usually fix it if you can get it apart, however the knocking has absolutely nothing to do with the secondary air pump."

Actually, the knock had everything to do with the secondary air pump. The knock was ONLY and I mean ONLY present when the secondary air injection pump was ON AND SQUEALING. Air injection pump on & squealing = knocking noise. No air injection pump on & squealing = no knock. Air injection pump on & NOT squealing = NO knock. The knock continued in spite of the oil treatment until I oiled the air injection pump. AFTER I lubed the air injection pump, the knock never occurred again.

Therefore, this whole problem was NEVER related to oil pressure. It was just a mis-diagnosis that sent me on a wild good chase.

As for all of the statements, "You're using the wrong oil". The Audi owner's manual and shop manual recommend 5W-40...but the only place to buy that around here is at the stealership and they probably want $10/quart (which I'm not paying). I can see that the 5W component is needed for the winter when it's below freezing and the 40 weight is needed for sustained 100 mph driving on the autobahn and oil temps climb to 250 degrees F. Here in Pennsylvania, the summer low temperatures are about 60 degrees F and the normal summer high temps are 80-85F, so the 10W-30 is plenty fluid in the summer. In the winter, I'll switch to 5W-30. I don't drive over 75 mph for sustained periods (...in Pennsylvania, you're lucky if you can do 65 with the crowded roads), so the (5W- or 10W-) 30 weight will be adequate year round. Light weight oils may pump easier, but at high temps they lose film strength, leading to engine wear.

This is my first Audi, but my last 3 cars were all VW 4-cylinder engines (Audi and VW are all the same engine block). Each of my cars had over 200,000 miles on them when I got rid of them and none of them were using more than 1/2 quart of oil per 1,000 miles (except the '79 Scirocco and who used synthetic oil back then?), so I know a thing or two about taking good care of an engine.

--Larry

 

its difficult to pin point a knock or squeal on the net so its trial and error and more down to you to explain better ( like exactly where the knock/squeal is coming from ) as for the oil synthetic is the best and there is no dispute on this but to say it looses its viscosity is totally untrue ( unless you change the oil every 15/20k or so ) but that's not to say basic oil is bad it just means you need to change it every 2.5k and the oil filter to prevent sludging