There are many factors to consider in that decision and the value of the car is pretty far down the list. The main question is the condition of the rest of the car and will there be another large repair right after this. If this failure was the result of driver error such as overheating, that wouldn't reflect on the rest of the car but if it just wore out from high mileage or lack of maintenance, that would be a different story.

You also need to consider your financial situation and what expenses can you handle. All cars represent an ongoing expense so the value of the car is not a big factor. How reliable it will be in the future is.