A8: 2.5 TDI AKE - Small Quirks & Issues

Good day.

I'm a trainee agricultural machinery mechatronics technician, and about six months ago I bought a 2001 Audi A8 with the 132kW 2.5 TDI engine. The car currently has 270,000 kilometers on the odometer, and it was serviced according to the Audi service book up to approximately 230,000 kilometers.

Generally, I am satisfied with the car; I haven't experienced any breakdowns or problems in the approximately 10,000 kilometers I've driven it. However, there are a few minor things that make me a little uneasy or simply pique my interest.

Regarding the starting behavior, there's nothing negative to say; the car warms up properly and always starts immediately and without any problems.
The engine runs smoothly, but there is a noticeable amount of noise, especially on the right bank, which seems to be coming from the camshafts (which are confirmed to be the original ones).

Here's a small list of 'issues' attached:

1. Whining noise under moderate load.
'The car makes a very loud howling noise, especially when it's cold. This happens both when the car is stationary and while it's moving. When stationary, the noise becomes audible around 1400 RPM and then becomes quieter again above 2200 RPM as the engine speed increases. To me, it feels like the noise is related to the turbocharger's boost pressure and only occurs at partial load. A video of the noise was commented on in an Audi group on Facebook, with one comment suggesting it might be 'carbon deposits on the exhaust side of the turbocharger, which wouldn't be a major issue.''

However, I'm not entirely sure about that. Generally, I get the impression that the car pulls according to its power output from around 2000 RPM. 230 km/h according to the speedometer is no problem (5-speed Tiptronic), but below 2000 RPM, it doesn't seem to have much power. It seems like the turbocharger isn't able to build up enough boost at that point, and you can hear how long it takes. Above 2000 RPM, you noticeably feel more power.

There's no indication that the turbo has already been replaced. To clarify, the car had a fault code ('VTG adjustment') after purchase, although I don't recall the exact details at the moment. We cleared the code, and it didn't reappear for about a month. Generally, I haven't experienced any warning lights or similar issues.

2. Engine water temperature in winter.
I know this is a controversial topic and there are many opinions on it, but I believe that a TDI engine should reach around 90°C after a certain amount of driving time, even at 0°C. However, in my case, this is not happening. I've observed that below 10°C, the water temperature rises to about 65°C and then stays there.
'Only by using a deflector plate in front of the radiator and driving in a slightly sporty manner can I achieve a water temperature of 85°C (according to the climate control code), even at 0°C. I previously checked the sensor values using a laser measuring device because I also had an issue with an intermittent short circuit on sensor G62. I currently suspect a faulty thermostat, but I haven't replaced it yet due to the significant amount of work involved.'

3. Change in the sound of the combustion.
'This is one of the things that, at least for me as a driver, isn't a direct problem right now, but it's still interesting to observe. The engine has a fairly consistent engine noise across all temperatures. The 'ticking' of the camshaft and the howling become quieter as the temperature rises, but the sound of the combustion remains the same. I only occasionally experience a minimal 'pinging' with a cold engine. What I find interesting is that the engine burns noticeably louder with gas pulses after it reaches a water temperature of approximately 75-80°C.'
The idle sounds the same, but when I accelerate the 'colder' engine, you only hear the gentle whir of the fan and a quiet combustion. Once the engine reaches 80°C, it sometimes starts to burn much louder and 'more aggressively,' which is most noticeable during sudden acceleration while idling. I mean, it doesn't sound bad or unhealthy, it just sounds a lot more powerful. The performance, fuel consumption, and driving behavior remain the same. I'm having trouble describing it.

If requested, I can try to provide videos of both the 'whining' and the 'roaring' sounds of the engine.
I don't have a 'diagnostic log' in VCDS for that vehicle yet. I'm not expecting any definitive diagnoses at this point, of course. But there are some interesting minor details, and maybe someone knows something about them or has experienced something similar.

Best regards, Henrik.

Hi.

Currently, I don't have much time to delve into this topic, but regarding the acceleration, I can only say that it's perfectly normal for this generation of V6 TDI engines that not much happens below 2000 RPM. If you want to get going quickly, you have to rev it up almost like a gasoline engine!

"My Audi A4 with 110 kW is like that, and it's even more extreme with my friend's 132 kW Passat 3BG. Everything is fine, but if you want to go fast, a 1.9 TDI is the way to go. The PD engines are best at low RPMs, but they tend to lose power quickly."

Thank you for the response, even if it's just a basic one.

I've had that thought before too. I can't really complain about over 2000 RPM; it feels like it accelerates well. The other day, I made a small comparison with an A6 2.5 AKE, which is also a bit lighter and only has 230,000 km on it, and it practically didn't perform any better.

I'm very familiar with the PD 1.9 engines; I had one in my first car (an A4 B6 with 96 kW, AWX engine). In terms of torque, they're small powerhouses, and compared to the 2.5-liter engine, they offer really good fuel economy.

Best regards, Henrik.

Hello.

First of all, your thermostat is broken.
In addition, the viscous fan often fails due to the...
failsafe principle remains active even in the event of a defect, consuming fuel and...
It also provides additional cooling for the engine.
The knocking sound you're hearing is likely due to a faulty needle lift solenoid.
to be attributed to.
Especially with short bursts of gas, it will accelerate like a tractor.
At 80 degrees, the motor control switches to "warm" mode.
Even with a functioning engine, this issue is noticeable. From that point on, the AKE (presumably an acronym for a specific system or component) should no longer be allowed to operate.
to nail.

I also think the thermostat is broken.
I already have the new one here, but because of...
...the effort has not yet been incorporated.

Based on your description, it sounds like there's a malfunction.
NHG, is that permanent nail art, or what?

Here are two more videos; I hope the audio is clear.

[Edit Admin: Eigene Videos etc. bitte im Thema hochladen!Bitte gib mir den deutschen Text, den du übersetzt haben möchtest.

It simply appears suddenly and doesn't show any other symptoms.
Symptoms. And it's interesting that it occurs when the device is not warm.
doesn't nail it at all.

If the needle lift sensor is defective, it will definitely store an error code in the diagnostic system.
Is he in there?

The video actually confirms my suspicion.
It sounds like the Visco is running continuously, and there's a knocking sound associated with the gas pulses.
Installing a new thermostat isn't as bad as it seems.
You don't even need to remove the timing belt, unlike what Audi recommends.
Do not buy cheap, imitation Viskolüfter fans. The parts with the coiled bimetal strip on the front are junk. The original part is from Hella-Behr and is available for around €90 in the aftermarket.
The problem with faulty needle lift injectors is that you can't dynamically adjust the fuel injection timing.

After a long, long time, here's another update about the car.

'I replaced the thermostat in February, but I left the timing belt in place because it's only 30,000 km old, and I didn't want to deal with the hassle of removing it. I marked everything, then carefully pried off a small piece of the crankshaft pulley and gently pushed it aside with a pry bar. It worked perfectly, and the car is running warm now.'

Regarding the topic of diesel engine knocking.

I hope this doesn't lead to the thread being closed, but I unfortunately don't have a diagnostic system yet. I definitely want to order one here, but as an apprentice, money is tight, and I can't afford the necessary amount right now. He doesn't have any acute problems.

I went to a friend who has a diagnostic tool, and he checked the car. There were no error codes in the engine control unit, neither for the throttle position sensor nor anything else.

After that, we checked the dynamic injection start and the fuel distributor, specifically the idle setting and then the timing from 0° to 18° before top dead center (if I remember correctly).

Clearly audible, the engine was quiet at 0° but made a very noticeable knocking sound at 18° (which is logical, since it was idling).

'Interestingly, the car wasn't warm enough due to the thermostat, so it was injecting at 0°, but the diagnostic system (Hella Gutmann) indicated that the target value was 12° before top dead center (BTDC) at a 70° engine temperature (while the engine was at 60°). In my opinion, the loud noise is likely due to the engine being in a warm-up phase. At 18°, the knocking was extreme, so it's somewhat quieter at 12°. When the engine is warm, it injects 12° BTDC, which is what it should be according to the diagnosis, and that would make sense.'

I haven't replaced the viscous fan yet. When the engine isn't fully warm, and you run it at a constant 2500-3000 RPM while it's idling, you can hear the viscous fan stop working after about 10 seconds. I'm going to leave it like that for now.


In the initial post, I mentioned 'Problem 1,' which is the engine noise.

I already bought a used loader back in January, with an estimated mileage of 100,000 to 150,000 kilometers, but I haven't installed it yet (as of today).

After 20,000 km with the car, the whining noise remained unchanged, and there were no other symptoms. Today, I decided to replace the turbos, and sure enough, the whining noise completely disappeared with the replacement turbocharger.


Generally, I have to say that the engine is running really well now; it no longer has any temperature problems, and it doesn't make that howling noise anymore. The only drawback is the rattling of the camshafts, but that's something that will have to wait a bit.


Okay, let's talk about something different. What about experiences with using 10W40 oil in the engine? At a meeting, an A6 driver told me that his 2.5-liter engine ran more smoothly with 10W40 and had less rattling, but I can't quite imagine that. Has anyone tried that before?

Best regards,