smell in cabin

[SWERVE]

got an e220cdi with 220000 miles on the clock i get a horrible burning smell in the cabin after about 40 miles i have changed the cat to turbo seal 8 quid from merc to see if it was exhaust fumes but to no avail.i am wondering if it could be the clutch burning out.car still pulls like a train and there is no noticable slipping from the clutch. any advice would be appreciated

 

[alanthewes]

Any oil dripping onto the exhaust from the gearbox?

 

[garyfishball]

H
It could be engine oil leaking from the rocket cover and dripping down on to the exhaust manifold!!
Check any oil leak from the engine block and dripping on the exhaust??
rgds
Gary

 

[Parrot of Doom]

Could be arcing across an electical contact, that often smells a bit fishy. Have a look at your fusebox.