Yeti Adventure 2015, 140 bhp. L/H

Started driving and became aware that there was fumes in cabin.  Drove aside and stopped the engine. There was some sort of fumes, not exhaust, rising from the very R/H corner, just behind the headlamp. Could not say for sure what kind of fumes it was. The fumes died out and we drove the 7.5 miles home without any trouble. The fumes came back then and is still coming if i try to start the engine. Suspected the heater (Webasto) at first but the fumes is there either on or off. What i also noticed during the way home was that the engine temp which is normally 90 degrees suddenly started to decrease to about 60-70 deg. before it returned to 90. Is this normal? Does anyone know what devices is "burried" in the RH corner of the engine compartment.  I am afraid something could have come loose when I accidently drove in som deep snow an hour earlier...😏

This may not be your problem but worth checking. When I had fumes in my Yeti it turned out to be an easy fix. On top of the engine three pipes each about 1cm diameter come together joined by a plastic "Tee" piece. I believe they are oil breather pipes. Although everything looked OK when I pulled the pipes to test their security I could feel some "give".There was a crack in the plastic tee piece letting fumes into the engine compartment and from there into the car. Having identified the problem a new part cost only a few pounds and took about 10 minutes to fit - I'm not much of a mechanic but the most important thing was not to let any of the broken plastic fall so slow and steady. I've not had a problem since. 

As I said, this may not be your problem but it is easy to check and you could then rule it out as a possible cause. Good luck. 

Many thanks for advise. I will check those pies and the T. Hopefully quick fix.