Ok so I check the heater core and hoses and everything under the rear seat.
The heater core makes a slight buzzing noise thats continuous, is this
normal?? There is no signs of any leaks or any punctures or anything..no green
or white marks round any of the connections everything looked tight.  My
question is if there is a leak somewhere else would it make only the rear
heater smell??  Any help on what it may be would be greatly appreciated.

Thanxs TIm G