I suspect my '99 v70's heater core is leaking, how do I check/ replace it?

Question

Do smell anti-freeze, carpet not wet, no windshield fogging yet

Answer 1

are your floors/carpet wet /discolored? does your windshield fog up with the defrost on ? coolant level keeps going down?
if yes to all the above then it is a good bet that you need a heater core. the whole dash bord will have to come out for access this is a big job how ever i have never had to replace a volvo heater core in 27+yrs of service.

Answer 2

do you smell antifreeze?