175k is getting up there. I would have to believe that more expensive repairs are in your not too distant future. I would replace it now. Go to a car selling site and look for cars with a lot of miles on them and see if there are lot of a certain make / model / year. If something sticks out, I would look for that same car with a lot less miles on it. The thought process is that if there are a lot of people selling that car with high mileage, well, then there ARE a lot of those cars that make it to high mileage and if you get one with under 100k on it, then you can get a lot of use out of that car still. Just an idea for you to consider.