CriticalCommonEngine

Audi A6: Oil sludge and clogged oil pickup screen starving the engine (1.8T 20v AEB/APU/AWT)

Oil sludge and clogged oil pickup screen starving the engine (1.8T 20v AEB/APU/AWT) is a common engine fault on the Audi A6 on the 1997–2004 cars, and we rate it critical. Putting it right costs $900 to $6,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 34 documented faults on the Audi A6.

Vehicle: Audi A6
Engine: 1.8L
Years: 1997–2004
Fuel: petrol
System: Engine

This page covers the Audi A6 as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Audi A6 faults34 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph of the Turbocharger or PCV / oil separator yet. We would rather show none than show a picture of a different part.

What goes wrong

The longitudinal 1.8T 20v fitted to the C5 A6 runs hot around the turbo and has a small sump, and on cars serviced on long intervals or with the wrong oil, carbon and sludge flake off the crankcase walls and breather system and block the oil pickup screen in the sump. Oil pressure then drops at higher revs, which can spin a bearing or kill the turbo without much warning beyond the oil light flickering. Caught early it is a sump-off clean, new pickup, new PCV breather hoses and a turbo oil feed line; ignored it means a replacement engine. VW/Audi extended warranty support in some markets for sludged 1.8Ts has long since expired.

What you would notice

Red oil can light flickering at idle when hot or under hard acceleration
Oil pressure warning chime with the engine warm
Thick black tar-like deposits under the oil filler cap
Ticking lifters that do not quieten after warm-up
Blue smoke or oil smell from the turbo side after a hard run

How to check it

Where to look. Engine sump and oil pickup under the engine; PCV breather hoses on top of the engine; turbo oil feed line at the back of the engine

Open the oil filler cap with the engine off and use a phone torch to look inside: shiny brown metal is good, a crust of black tar or grey mayonnaise is the warning sign.
Pull the dipstick and check the oil is not black and gritty.
Look at the service book for oil changes every 10,000 km or less on fully synthetic oil that meets VW 502.00; long gaps or cheap oil are the risk factor.
With the engine hot after the test drive, let it idle for a few minutes and watch the dash for any flicker of the red oil light, then blip the throttle and watch again.
If a workshop inspection is possible: have the sump dropped to inspect the pickup screen, fit a mechanical oil pressure gauge to read pressure hot at idle and 2,000+ rpm, and check the PCV breather hoses for cracks and blockage.

Parts involved: Turbocharger, PCV / oil separator.

What it costs to put right

$900 to $6,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“How often was the oil changed and what oil was used?”
“Has the oil pickup screen or sump ever been cleaned out?”
“Has the oil light ever come on or flickered?”
“Have the PCV breather hoses been replaced?”

Now check the Audi A6 you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

Audizine: 1.8t Oil Pressure Survival Guide and troubleshooting DIY (thread 610203)
Audizine: Red Oil death light and results of fixing the problem (pickup screen)
Bob Is The Oil Guy forum: My 1.8 Engine And Sludge
AudiWorld: A4 B5 platform, Oil Pressure problem thread

Audi A6 buyer questions

Is oil sludge and clogged oil pickup screen starving the engine (1.8t 20v aeb/apu/awt) serious on a Audi A6?

We rate it critical and common on the Audi A6. The longitudinal 1.8T 20v fitted to the C5 A6 runs hot around the turbo and has a small sump, and on cars serviced on long intervals or with the wrong oil, carbon and sludge flake off the crankcase walls and breather system and block the oil pickup screen in the sump. Oil pressure then drops at higher revs, which can spin a bearing or kill the turbo without much warning beyond the oil light flickering. Caught early it is a sump-off clean, new pickup, new PCV breather hoses and a turbo oil feed line; ignored it means a replacement engine. VW/Audi extended warranty support in some markets for sludged 1.8Ts has long since expired.

How much does it cost to fix on a Audi A6?

$900 to $6,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Audi A6 years are affected?

Our research records this fault on the 1997–2004 Audi A6. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Open the oil filler cap with the engine off and use a phone torch to look inside: shiny brown metal is good, a crust of black tar or grey mayonnaise is the warning sign. Pull the dipstick and check the oil is not black and gritty. Look at the service book for oil changes every 10,000 km or less on fully synthetic oil that meets VW 502.00; long gaps or cheap oil are the risk factor. With the engine hot after the test drive, let it idle for a few minutes and watch the dash for any flicker of the red oil light, then blip the throttle and watch again. If a workshop inspection is possible: have the sump dropped to inspect the pickup screen, fit a mechanical oil pressure gauge to read pressure hot at idle and 2,000+ rpm, and check the PCV breather hoses for cracks and blockage. Look here: Engine sump and oil pickup under the engine; PCV breather hoses on top of the engine; turbo oil feed line at the back of the engine