I hope someone can help with this out there because it is really begining to get annoying...... :D For about the past year or so my C3 (exclusive 1.4HDI 02) has been making a strange hissing/tapping/ticking type of noise from somewhere in the engine, it seems to be coming from the back right side of the engine as you look at it behind the main block. This has progressively got worse and mainly over this past weekend seemed to get even worse. This noise also follows the revs of the engine. There has always been a faint chemically/exhaust gas type of smell coming through into the car. Previous questions to normally been met with the answer "if its not effecting performance don't worry" I had the EGR valve replaced in May and asked the mechanic to have a look around then but unfortunately he couldn't put his finger on anything. Since then it has been for an MOT, which it passed, but 2 different mechanics there couldn't pinpoint anything either. I have noticed over the past few months that it does not seem to be running as warm as it used to (don't know if this would have any effect). I used to get 3 lights on the dashboard temp gauge pretty much all the time but now I only ever seem to get 2 apart from the odd occasion. I do mainly motorway miles so it should have ample time to warm up. Looking through the forum there are a couple of similar posts so hopefully someone can give me some suggestions to take to my mechanic? I wasn't sure whether it could be the injectors having diesel in or something connected to the air con as this has developed a strange smell (although not too sure if it needs re-gassing). I am still getting a decent fuel econ (69-72 though driven a little gingerly) so not I'm not worrying there but wouldn't like it to turn out to be something major? Thanks in anticipation :( Marc