When to stop putting money in a car?

I have 2007 Ford Explorer with 90k miles. I took it in to a dealer 1 month ago because it was squeaking and they replaced the serpentine belt and tensioners for $350. It was squeaking again yesterday so I took it in and they said they have to replace the harmonic damper for $800. Now they call and say they found a leak in the radiator so that will be another $700 to replace.

I don't know what to do… I feel like they will just tell me I need something else in a month. At what point should I stop putting money in a car?

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