One of the first words you use in your dream account is "exposed." So here we have a hint that something is going to be revealed that isn't necessarily apparent at the "front end." Well, we often put on something of a false front, which Jung called "the persona"---but dreams show us what's behind it---like good mechanics, they take a nice long peek under the hood.
So, let's take a look at the inside of your psyche. First, there's a fear of something coming loose; you're worried the motor might separate from the car entirely. The motor would be running, but the car wouldn't be going anywhere. Do you talk a good game, but wonder if you're actually getting anywhere? But the bolt, you say, "turned freely"--in fact, you use the word freely twice in one sentence. Maybe your dream is saying you need to shake things up a little, "twist loose," even if you fear, as we so often do, something negative might happen. You might be pleasantly surprised at what happens next.