Re: M25 what is this and where does the hose go?
The little unit there is your breather element for the valve cover. It should have a hose that attaches to the elbow and runs down through a small bracket. If I remember correctly it does not attach to anything, just terminates below the engine. Its purpose is to vent any air pressure built up in the head cover or as it is normally called here in the US the valve cover. See the PDF file on the web page attached here for a full parts list. You will find the doohickey in question on page 16 of the PDF, but the actual manual page is 12, the part numbers show on the next page. Please note that there are some filter elements on the inside of the head cover that should be in place to prevent it from making a mess in the engine compartment and these need to be in good order. Just download the PDF and print it out for your future reference.
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