Leak detection in the Audi 80 TDI charging system

Hello forum,

Besides the annoying idle shudder I've gotten used to over the past 20,000 km, I've also been experiencing a loud, whooshing noise for a few days now. My suspicion immediately falls on a leak near the turbocharger, as the noise starts exactly where the turbo begins to boost.

But:

1. Ich find bis jetzt kein Leck. Habe den Luftfilterkasten abgebaut und die Druckschläuche so weit es geht abgefühlt (im Lehrlauf voll aufs Gas gestiegen, VAGCOM hat irgendwas über 1500 mbar gemeldet). Nichts. Leider verchwindet das Druckrohr da irgendwo im Nirwana unter dem Luftfilterkasten in der Karosserie, mit ganz langem Arm komm ich bis ans Druckrohrende an einen Kasten : Ist das mein LLK? Muss ich etwa um da halbwegs dranzukommen den Kotflügel abschrauben und den Motor rausnehmen!? Wo verlaufen die Druckrohre zwischen LLK und Turbo? I would be very grateful for a small hint.

'At full throttle without any load, I'm seeing over 1500 mbar of boost pressure according to VAGCOM (I haven't measured it precisely), but I don't hear any noise! When driving (I'll do a proper test drive tomorrow), the noise is very noticeable when you exceed half throttle. Question: What else could be causing the noise? Could it possibly be my automatic transmission?'

'After 10 seconds of full throttle / reaching 180 km/h, the car always abruptly switches to limp mode or reduces power > 150 km/h. I suspect it's either my fuel injection pump (causing idling issues and fluctuating fuel delivery) or the EGR valve. While I don't think it's related to the whistling sound, excessive boost pressure could also be causing it...'

4. On the engine, near the crankshaft housing ventilation system, there's a container (approximately 8 cm in diameter) where a significant amount of oil is leaking out. What is the purpose of this container?

I appreciate any suggestions you might have – I'm hoping to get as far as possible this weekend.

Best regards,

Rainer.

Regarding point 4.

'Oil also leaks out of this container for me, and I'm unfortunately unable to say what it's for, but it doesn't seem to have any negative impact on the engine's performance!'

Sure, here is the translation of the text from German to English:

'MFG' stands for 'Mit freundlichen Grüßen,' which translates to 'Sincerely' or 'Best regards' in English. It is a common way to end a formal letter or email.

Hi,

zu 3) Notlauf = Fehlerspeichereintrag. Which one?

Best regards, Rainer.

Hello Rainer,

I couldn't find any error codes, but maybe they will be cleared later.
Okay, so when I'm driving around 180 km/h, the engine makes some kind of noise after a few seconds.
'unclean,' so that it can only maintain approximately 150-160 km/h. If I then release the accelerator (even for a second or two), it returns to full power. I'll probably have to read the error codes while driving on the highway... maybe I'll be able to do it tomorrow on my way to work, if it doesn't snow!

Thank you for the answers!

Rainer.

Sure, here is the translation of the text from German to English:

"To 1:"
Yes, that's the LLK (likely referring to a specific piece of equipment). The pipes just run straight down. It's easy to access from below!

Sure, here is the translation of the text from German to English:

"For question 2:"
Okay, let's bleed the pipe system! There are already many descriptions available on how to do that.

To question 4:
As far as I know, there's a valve and a filter inside to separate the oil.

Hello everyone,

I finished my homework today... The measurements showed that I have far too little charging pressure.

Engine speed | Specified manifold absolute pressure (MAP) | Actual manifold absolute pressure (MAP) | Duty cycle
all 1's = off Boost Valve
/min mbar mbar %
2583.00 1630.00 1378.00 39.8
2625.00 1814.00 1579.00 39.8
2646.00 1856.00 1571.00 39.8
2667.00 1873.00 1579.00 39.8
2709.00 1882.00 1588.00 39.8
2751.00 1873.00 1588.00 39.8
2793.00 1873.00 1588.00 39.8
2835.00 1873.00 1596.00 39.8
2877.00 1882.00 1604.00 39.8
2940.00 1882.00 1613.00 39.8
3003.00 1882.00 1621.00 39.8
3045.00 1873.00 1630.00 39.8
3108.00 1873.00 1638.00 39.8
3171.00 1882.00 1646.00 39.8
3234.00 1882.00 1655.00 39.8
3276.00 1882.00 1663.00 39.8
3318.00 1890.00 1663.00 39.8
3381.00 1898.00 1663.00 39.8
3402.00 1898.00 1663.00 39.8
3444.00 1898.00 1672.00 39.8
3465.00 1898.00 1663.00 39.8

When idling, and even when I gently press the accelerator, it's noticeable that the charging indicator doesn't start working immediately.

Engine speed | Specified manifold absolute pressure (MAP) | Actual manifold absolute pressure (MAP) | Duty cycle
861-945 Pressure Boost Valve
/min mbar mbar %
777.00 966.00 991.00 92.2
840.00 974.00 991.00 92.2
777.00 974.00 991.00 91.8
1470.00 1084.00 991.00 72.7
2478.00 1142.00 1084.00 69.5
2373.00 1092.00 1058.00 67.2
2310.00 1092.00 1050.00 63.7
2310.00 1092.00 1042.00 59.4
2310.00 1092.00 1042.00 55.1
1827.00 1075.00 1042.00 53.9
882.00 991.00 1008.00 57.8
819.00 983.00 991.00 60.2
756.00 974.00 1000.00 62.1



Regarding the injection timing, I don't think that's right either. According to the table on the forum, it should probably be closer to 3-4 degrees before top dead center (BTDC).

Specified start: Actual start.
2 to -3 2 to -3
° °
-0.4 1.0
-0.4 0.8
-0.4 0.7
-0.4 0.8
-0.4 1.0
-0.4 0.7
-0.6 0.7
-0.6 0.7
-0.6 0.7

I continued searching for a leak, but honestly: if there's a pressure drop of over 0.2 bar, it's not likely to be caused by a small hole in the hose, right? I'm pretty sure it's my LLK (likely referring to a coolant reservoir or similar component). What do you think? I'll check it tomorrow; it got too dark today.


If the coolant system isn't a huge leak, what else could it be?

Thank you for your suggestions!

Rainer.

Hello everyone,

After searching for a while, I finally found the leak: The hose connector to the inlet had a crack, specifically on the side facing the engine block.
On the page you mentioned, I couldn't quite bring myself to do it...

Perhaps I can still contribute something useful to the discussion about printing.

Mann kann ser wohl mit einer kleinen Luftpumpe prüfen ob das System Luft hält (Positivbeweis). Wenn man aber ein Leck hat wird man dies so kaum finden da man einfach nicht den nötigen Massenstrom hinkriegt. Da wird man nur schwer einen Lufthauch fühlen können, und die Seifenblasen werden schneller weg sein als ihr gucken könnt wenn ihr das Pumpen aufhört. Also besser: Kompressor. Oder I went straight for the turbo boost; that's what I did.

Close the last hose before the inlet and start the engine. I had increased the throttle slightly because I was working alone, so the engine was running at approximately 2000 RPM. And sure enough, as I held the open end of the hose, I felt the leakage current.

So, if your system builds up pressure on its own with an air pump, it's probably very airtight. However, if you need to find a leak, use mass flow measurement combined with pressure readings!

Okay, so it's now back to around 1850-1950 mbar. The whistling sound is gone (I'm curious how long the duct tape will last; I still need to get a new hose from the dealer). I'll accept that it can't keep up with the target pressure below 2000 rpm as a system weakness; the turbo just isn't delivering enough boost, right?

Thank you very much for your suggestions! I'll take care of that soon.

Best regards to everyone,

Rainer.

Quote:

I increased the throttle a bit because I was working alone, so the engine ran at approximately 2000 RPM.

Original .
Well, you found it that way.

If you're logging data again, it's best to do so in 3rd gear, between 1,400 and 4,000 RPM. This range is optimal for identifying any deviations in boost pressure and potential inconsistencies during engine warm-up.

And yes, it's normal for the loader to lag behind the target speed in the lower RPM range.