overhaul, over all, overall, overalls

Overall or overall ( one word ) means including everything; covering every part or facet, literally or figuratively--
Overall, the bridge is about 100 feet long.
After his vacation, he was left with an overall sense of well-being.

Over all or over all ( two words ) means above in place or position ( over ) everything or everyone ( all )--
The same sun shines over all of the Earth, but not at the same time.

Over all may also mean through all  of ( over ) everything ( all )--
I'll get back to you in a day or two, when I have looked over all of the papers you sent.

Over all may also mean covering ( over ) everything ot everyone ( all )--
Find a blanket big enough to spread over all of the children.

Overhaul or overhaul ( rhymes with overall ) means to check all parts and perform necessary repairs and maintenance, literally or figuratively--
We will have to overhaul the furnace before the weather gets cold.
The board is planning to overhaul the company bylaws.

Now that you know that, you can say--
"We've looked over all the records, and we'll need to have an overall safety check, and we'll schedule an overhaul  of the machinery."

Note--"overalls" means a garment with trousers attached to a bib, held up by straps--
The baby needs some overalls now that he's crawling; pants slow him down.
He looked like a farmer, in denim overalls and a straw hat.

Not to be confused with "overhauls", the third person singular ( he, she, it ) form of "overhaul", meaning to check all parts and repair where necessary--
Our mechanic overhauls the car every year before we go on vacation.