There are several synonyms for the phrase "bucket of bolts", which is often used to describe something that is old, worn-out and unreliable. Some of the possible alternatives include "clunker", "jalopy", "heap", "wreck", and "rust bucket". All of these terms suggest that the object in question is not in good working order and may be prone to breaking down or malfunctioning. Other possible synonyms might include "lemon", "heap of junk", or "beat-up old car". Regardless of which phrase is used, the implication is that the object being described is not worth much and may even be considered a liability or danger.