21: Subaru Forester
Forester owners face all kinds of problems including head gasket failures and overheating. The Forester is reliable when it has low mileage on the odometer, but as the car ages, these problems tend to spring up (via Hot Cars).
Another problem with the early Forester models is rust, which tends to target the wheel wells of the car. This is another well-known problem Subaru has acknowledged, and it will break drivers’ budgets to get it taken care of.