I agree with Caymen on this.
$2k or $3k (worst-case) now, even if that has to be done (verify first), is better than the same amount as a down payment and then a new car payment for the next 5 years, unless of course you WANT a new car and can comfortably afford a new car payment.
Only you can determine how much longer you want the ST.
We had a Chrysler mini-van that we drove for almost 4 years after being paid off. It was cheap to begin with. Around year 5 we starting putting about $800/year into it.
American made cars, heck all cars for that matter, will require some signfiicant, ongoing maintenance after the warranty period expires. Water pumps; fuel pumps; transmissions; pulley assemblies; alternator; etc, etc. Many of these worn part replacements can be done yourself with basic tools (an alternator for example it typically easy), others cannot, as they require special tools, a lift, and/or more advanced mechanical skills.
Many Americans drop a car after 4 or 5 years just to avoid getting "nickeled and dimed", and others get a new car for the "peace of mind" that comes from having something that shouldn't need any type of major repair for several years.
But, as Caymen said, you probably would be money ahead to keep the ST and keep it repaired. That only leaves how much your "peace of mind" is worth to you.
Safety; control; the feeling that your vehicle is reliable and nothing will break within it for years...these are all illusions -- things that we conjure up in our mind to help us cope and make it through the day.
TJR
