Oil pressure suddenly dropped to zero at 1z TDI!

Hello everyone, I'm currently sitting in an internet cafe on Crete. When I arrived at the airport, my 1z bus in Terminal 3 let me down.

After driving for 10 km, the oil pressure warning light suddenly came on, and my oil pressure gauge showed 0 bar.

I have a 1z engine in a T3 with an additional oil cooler. The engine has approximately 60,000 km, with approximately 30,000 km in a bus. 500 km ago, I changed the oil and installed a Bosch oil filter. Oil consumption so far is approximately 1 liter per 5,000 km. Oil is sufficient in the tub, there are no leaks or other losses.

What could it be?

Can the thermostat for the external oil cooler be completely closed?
Or can the turbocharger seal suddenly fail?
I'm really at a loss. The engine was running smoothly, with no noise, no smoke, and no increased temperature.

[Translating...]Könnte die Ölpumpe defekt sein?

Kenn mich in dem Bereich nicht aus, aber vielleicht wäre es eine Überlegung wert.

Hello Joe,

Where do you take the oil pressure for your dynamic display and what type of thermostat do you use for your oil cooler?
I am not aware of a coolant thermostat that can completely shut off the oil circuit, as there are always bypass openings. The oil filter, if clogged, also has a bypass opening. If the oil pressure is reduced at the oil filter flange, then the filter is clogged (but the engine will still be supplied with oil via the filter bypass)!!!
If the oil pressure at the cylinder head (where one of the sensors for the oil pressure gauge is located) is actually zero or very close to zero, then the hydraulic lifters should make a very loud rattling noise (similar to the first few seconds after an oil change). If this is not the case, I would assume that there is a faulty measurement. A motor that runs without oil pressure will become louder and rougher shortly after the oil pressure drops.
I once had a similar case: The oil pressure switch and the dynamic oil pressure sensor were mounted on a T-piece at the end of the cylinder head. An oil sludge clump had blocked the entrance to the T-piece, causing the red light to suddenly illuminate and the oil pressure gauge needle to drop to 0 bar.

Have a wonderful vacation!!!!

[Translating...]

Hallo,

hast Du schon den Öldruckgeber durchgemessen ? Kabel dorthin ok ?

Grüße, Rainer

Hello, Thank you for your responses, here are some additional details:

The VDO oil pressure gauge is mounted on the oil pressure flange.
I bought the oil cooler thermostat from Reinhold Mayer, who offers oil coolers for T3 buses.

The bus was, of course, immediately stopped and towed home, I am currently still in Greece and trying to figure out the cause (therefore, I also can't write umlauts, Greek keyboard)

Where is the oil filter bypass? Is there then no pressure on the oil filter flange?