Sounds when shutting off the engine

I recently bought a 2000 Seat Ibiza TDI with 81kW. Now I've noticed that it makes a noise when I stop the engine. In my opinion, the noise is coming from the turbocharger. That is, even when the engine is off, the turbo is still running. Is this normal to hear so clearly? In my old Golf III TDI, I didn't notice this. It's also not the case that I immediately stop the engine after full load. The noise always occurs. Has anyone else experienced this?

Hi,

my car also makes a quiet humming noise after being parked.

I think the noise could be coming from either the alternator or the starter motor. The alternator has a free-wheeling mechanism that can also make some noise (test: remove the belt, spin the alternator by hand, and then hold the wheel).

If you can hear the noise clearly, you can try another test:

Start the engine, then immediately turn it off and pay attention to how long the noise lasts.

Then, try the same thing with the alternator's regulator cable disconnected. If the noise is now longer, it's coming from the alternator because its stored energy isn't being converted into battery charging, so it continues to run for longer.

I'll try this on my car too when I have a chance.

I initially suspected the Lima was the culprit. However, it's clearly coming from the Turbo system. I'm surprised that it didn't affect my Golf at the time, or that it didn't have this issue. I'll talk to the dealer in the coming days. I have a used car warranty, so I'll report back on what he tells me.

See you later.

Hi

[quote]
This definitely sounds like it's coming from the Turbo side. I'm surprised that it didn't affect my Golf at the time, or that it wasn't present. I'll probably talk to the dealer in a few days. I have a used car warranty, so I'll report back on what they tell me.
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
If the trip to the dealer is longer than 5 km, I would consider it a waste of time and money, as the answer would likely be "as long as there is no performance issue, the charger is okay".

A more precise (own!) check would, of course, be possible with a boost pressure gauge.
But why would you build a standard instrument to monitor a (relatively sensitive) function that is essential for the TDI's performance - that would only create more annoying questions...

Hi Ulf,

Hey, did you also disconnect your EGR valve? I've found that the turbo only runs for as long as I disconnect the EGR. I've put it back on for now, just to be safe. I think it's better for the turbo. I think the turbo runs longer at higher idle speeds when the EGR is disconnected, because the exhaust manifold has more pressure when the EGR isn't diverting exhaust gases into the intake. This probably makes the turbo spin faster at idle, and therefore run longer.

Hello everyone!

[quote='schroederliese']
Hey Ulf,

Ich denke, dass der Turbolader mit der AGR-Klappe geschlossen mehr Leerlaufdrehzahl ermöglicht, da der Druck im Auspuffkrümmer größer ist, da die Abgasrückführung keine Abgase in den Ansaugkanal leitet. Dadurch dreht sich der Turbolader im Leerlauf wahrscheinlich schneller und läuft somit länger.
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
Interesting theory! That could also be an explanation for faster response to the accelerator pedal with the AGR blocked, as there would be more exhaust gas available for the turbocharger.

As for the noises after the engine is switched off, I only hear a hissing sound from the air conditioning.

Best regards,
Udo

[quote="schroederliese"]
Hi Ulf,

Hey, did you also disconnect your EGR valve? I've found that the turbo only runs for as long as I disconnect the EGR. I've put it back on for now, just to be safe. I think it's better for the turbo. I think the turbo runs longer at higher idle speeds when the EGR is disconnected, because the exhaust manifold has more pressure when the EGR isn't diverting exhaust gases into the intake. This probably makes the turbo spin faster at idle, and therefore run longer.
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
Hi

I've also been experiencing around 0.05 bar of pressure in the engine idle, but only when the engine is warm, due to a faulty AGR. Apparently, the oil is too viscous when cold to allow the turbocharger to spool up with the small amount of exhaust gas flow at idle.
However, even with a hot engine, the pressure drops to "zero" within about 1 second after shutting off. I just think that's enough oil in the bearings for these "few turbocharger revolutions".

Incidentally: if a turbocharger bearing is starting to wear, then, IMO, the warm idle boost pressure should decrease first as a result of the increased friction.
As long as I don't observe anything like that, I won't be repairing my AGR

It's really helpful to see the boost pressure

Hi,

I'm pretty sure I've heard the exact same noise in my
Seat Leon TDI 110 hp. With a faulty AGR valve, you can clearly hear the turbo
running after the engine is warm, but only when it's warm.
That's why I re-repaired the AGR valve.

Is this only a problem with Seat cars?

One more question:
Do you have to let the turbo
run after the engine is switched off these days?

Regards, Achim

Hi

[quote]Does one still have to run the turbo after today before shutting down the engine? [/quote]
If you drive 5 km uphill with a full load, then brake hard into a parking space, and immediately turn off the engine, the turbocharger will still be almost red-hot while the oil circuit stops circulating.
Then the oil in the turbocharger bearing will evaporate and leave an oil residue. If you repeat this process 5 (?) times, the turbocharger will be seized – even a cooling fan controlled by the engine computer won't help.

Therefore, drive more gently in the last few minutes (so that the turbocharger can cool down with circulating oil), then you can immediately turn off the engine after about 3 seconds of idling.

The new TDI's have a throttle valve located in the 'intake' manifold. Perhaps that's the source of the unfamiliar/unusual noise!

It only blocks the flow channel when the engine is switched off.