Coolant Problem VW Passat

Hello everyone,

I'm having a coolant problem with my Passat Variant TDI 90 hp, manufactured in 09/97. I recently filled the coolant up to the maximum level. Now, the level has dropped significantly to below the bottom edge of the expansion tank, where the hoses are connected. However, the coolant level is now stable. I only lose coolant when I refill it, and then it drains out relatively quickly. I can't find anything obvious. There's just a slightly oily residue on the bracket under the expansion tank. I had a similar problem with my Golf a few years ago, and in that case, the tank had a hairline crack. However, the shape of the expansion tank on the Passat is different, and it's securely mounted with three screws.
'I have a question for you all: Has anyone here ever experienced a leaking expansion tank on a Passat? I'm hesitant to buy one myself. I would appreciate any advice.'

Best regards, Franz.

I had a leaky hose on my car. It was really difficult to find the hole.
I basically ran my hand along each coolant hose, and at the same time, I pressed on the hose near the radiator with my other hand, creating pressure in the system. That's how I accidentally found the tiny hole, which was in a slight bend of the hose. It wasn't visible to the eye and seemed to only leak under higher pressure.