After a look into the engine compartment, a first error was quickly found: the hose (marked in the photo, example photo) has been patched up many times and is now broken again in one place. Guess we should just replace it. Now I’m not from the compartment and I would like to know about its function and maybe someone can tell me the part number or just how the thing is called so that I can can order without first having to drive to the friendly. Thanks and best regards