Coolant smell with heat on?

[74Stylez]

Hello all,

1999 ML430, 217,436 miles. I live in Chicagoland and I have been smelling faint antifreeze with heat on this winter.

Friend with similar smell on 1999 Subie Legacy Outback just blew head gasket, (although she was leaking antifreeze onto ground and changed water pump and thermostat prior), I am hoping I don't have the same future in store!

I am not leaking any antifreeze and I have not noticed a change in level in coolant reservoir. I drained/refilled radiator and engine block this past summer. I have not changed hoses, but they are not soft or bulging around clamps. Original water pump and thermostat still on truck.

Thanks for any help.