overhaul
verbUK /ˌəʊvəˈhɔːl/
US /ˌoʊvərˈhɔːl/
To overhaul something means to fix it up or change it a lot so it works better.
The old car was so broken that the mechanic had to overhaul the whole engine.
OTHER MEANINGS
2. A complete change or improvement made to a system or machine.
The school announced a major overhaul of its lunch program.
3. To catch up with and pass someone or something.
The runner overhauled the leader in the final lap.
4. To examine something carefully to find and fix problems.
Experts came to overhaul the factory's safety rules.