Have a 3 year old Husqvarna self-propelled walk behind mower. Has been a good mower. Changed oil yearly, replaced the drive belt once, and winterize it each fall before putting it away. My daughter was mowing last week. Her testimony - "It made some pinging noise and then oil started dripping onto the top of the housing." She turned it off as soon as she saw the oil. The repair shop (slow to do anything) said it may possibly be the oil breather is clogged. I started it at the shop and it smoked badly for the 5 seconds I let it run. Is the shop's diagnosis, without taking anything apart a possibility and is it a self-repair job?