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Robert, UK Qualified Car Technician
Category: Car
Satisfied Customers: 4716
Experience:  Fully qualified / self employed garage technician in the UK
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I get a strange smell under bonnet & in the cab when the heater

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I get a strange smell under bonnet & in the cab when the heater vents are open, does' nt smell like engine but more chemical type smell like something burning off the exhaust.
Customer: replied 2 years ago.
No smoke coming out of exhaust or around cab.
Customer: replied 2 years ago.
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Have you noticed at all any leaks on the engine or from under the engine when parked up?
Any engine temperature issues that youve noticed?
Does this only heppen when the blower fan itself is in use?
Customer: replied 2 years ago.
Hi Robert, No oil leaks, no problems with engine temp, drove 50 miles up M3 at 62 mph, sweet as, but I noticed the smell when I stopped at petrol station to fill up. The smell is there always but made worse in cab when vents are open especially when heater is turned up, much better when on cold.
Ok..By the sounds of it id say you may actually have small coolant leak,or hot coolant your smelling - this depends on the severity of the leak of course if there is one..if its quite small then obviously with the heat of the engine or associated parts ie: exhaust manifold which will be very hot..then it will just evoporate and thus you may end up getting that smell to drift into the cabin with forward motion of the vehicle and maybe too at a stand still you might smell it too...Id say from that is check you coolant level from cold engine and see if it has indeed dropped - also inspect the cap and the seal just to be sure its not that causing the problem.... other factors would be check the wiring and wiring harnesses around the engine just incase its not actually a electrical buring smell..especially if you've had any aftermarket devices fitted recently it would be worth to inspect them carefully.... Id imagine if it was petrol or oil you would know that straight away..but going by your desription id say it would be worth while for an inspection of the entire coolant system aswell as the heater matrix..if need be..then ask to get a "coolant system pressure test" done on the coolant system as this will highlight any drop in pressure caused by a possible leak thats causing the smell it will also help highlight the potential for any leaks on the coolant system itself..
Aswell as too inspect the wiring within the engine bay aswell as any fuse panels just to rule them out anyway..thats what i would do if this was in front of me and based on all other factors like engine leaks ie: fuel or oil or gasket leaks etc was all ruled out....then leading to an inspection of the engine belts for possible issues there..then to the front end braking system to be sure there no potential brake binding problems on the front causing there is alot of options to rule out..but considering i cant experiance it myself then i can only give possible areas of inspection above to be carried out..but id imagine can all be done on diy bases bar the pressure test of course if you dont have the equipment..I do hope this helps
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Customer: replied 2 years ago.
Thanks I will check.