Many automakers provide dealers with an annual budget for goodwill gestures to what the dealership perceives as loyal customers. General Motors in particular has increased its pool of funds for this purpose as one way of trying to increase loyalty among its customers. Brand loyalty has been a top priority with many automakers over the years, but in today's highly competitive market for a car shopper's business, it is considered to be critical by many automakers as well as individual dealerships.
Getting a free repair can be a delicate situation, but certainly well worth pursuing. While there's really no limit to what kind of repair can be completed for free, you are most likely to get a free repair if your car is recently out of warranty, and it's a repair that would have previously been covered under the warranty. Still, it is possible to get a free repair on a car where the warranty has long expired or on something that was never covered under warranty.
You might be pleasantly surprised to simply find a zero balance for a repair you've requested, especially if you've made it known in the service department that you've been a loyal customer of that dealership or that car brand for a while. Still, you may need to ask politely if there's anything the service manager can do to help you out of this unexpected expense. Sometimes a simple, "Wouldn't that have been covered under my warranty?" can get the point across.
Because getting a free car repair is completely up to the dealership's discretion, being polite and not demanding is the best approach. Reminding them of your loyalty to their store or the car company might be helpful. If you don't get anywhere, you also might ask the service adviser to check with the service manager or the regional field representative, who may be able to authorize the free repair.