In short, no they need your consent to perform the work. You don't say the year make, model, value of the car, that might matter here as to what you do. And with that info someone can comment on this repair and the process. Depending on the car a used engine might the cheaper way to go, or junk the car and buy another one. They know all this, so this situation is odd. I wonder if they have actually sent the heads off and not just trying to fake bill and have you say keep the car. Testing the heads, that can be done by a local machine shop/engine rebuild shop in most cities.

Ok, this is civil matter not criminal, so the term legal is not exactly right. Lets assume there really was some miscommunication and they are not working a scam. There no set required process for the way people manage car repair quotes and requests, which I think is what you are getting at, that they broke some required process. Some places I go to, especially chain shops, provide a written quote, and if is a large repair may require you to initial the work estimate, and if they have to incur special costs may ask for a down payment. Some smaller shops that know me I drop of the car at night, leave the keys with note, they call me when the repair is made or if they find some other problems.

So this is a contract dispute. They say you had a contract you say no contract exists.

Based on value of the, the best idea is to meet with an attorney, now please do not do what some people do, yell and scream I'm going to sue you. That does nothing. Either hire an attorney or don't. Lets say you pay an attorney $300, he/she writes a letter and the shop agrees to pay you the value of that car with a blown head gasket. In my book that would be a win.

If is a low value car you write a letter, keep a copy, mail a copy and drop off a copy. Write, "I did not authorize any repairs on vehicle ABC, and in fact explicitly said I could not afford a major repair and to not do any work. I was never provided a written estimate nor signed any work authorization. Please collect all the parts put them in the trunk of the car and will have it towed off your lot at my expense. At that time I will consider this matter closed. "

You need to read up on mechanics liens in your state. Usually a mechanic can put a lien on a car for non payment of repairs, but they have to go through a process and notification for that. I don't think that allows them to hold the car, ie not release it to you. They may think that and imply that and actually do that to customers to force them to pay, but I am thinking if they do not release the car and the police are called they should say release the car to the owner, she is the legal owner, any other dispute related to billing, work quality, etc, you two can settle in court if needed.

Your other option is to file a small claims court case and ask that they pay the value of the car at time you gave it to them. Say is worth 3000 normal and 1200 with a blown head gasket, you ask for 1200. Because if they don't take apart the car you could have sold it for 1200.

Hope it works out.

If you did not sign a repair order with an estimate of 1200.00 dollars you don't owe them anything. go get your car if they refuse call a cop. without consent they can't do a mechanics lean and they inevitably fixed your car for free. that's how it is in my state and most states to my understanding. call the better business bureau and report them.

Call your States Attorney General office of consumer fraud or consumer protection and ask them the specific laws for your state.

Try googling your state's name and "auto repair laws"

For WA where I live, you find this

http://www.atg.wa.gov/consumerissues/car...

You are entitled to a written price estimate for the repairs you have authorized before the work is performed, only if you deal face-to-face with the facility and the work is expected to cost more than $100. Once you receive an estimate, the facility may not charge you more than 10% above the estimated costs without your prior approval.

I'm not sure the police will help you, this is a civil matter, not criminal.

ask them for a signed work order.

So I was driving my car and it started overheating very frequently. My mom's friend is a mechanic and took a look at it. He said it was probably a head gasket and so i took it to a local car repair shop just to get a second opinion. I told them i wanted an oil change and for them to take a look at the engine. I NEVER said i wanted any repairs done, just a quick inspection to see if they could confirm. They told me to leave it there overnight so they could let the engine cool before checking it. The guy promised nothing they did would be over $80 without my consent. I came back the next day and they told me it was indeed the head gasket and that the first thing i had to do was send the heads to a factory to see if they were "warped". I denied and said i couldn't because i knew they would charge a ton just to send the heads away. They said there was no way i could drive it home without damaging it more. My mom called them back 2 days later on Monday(they were closed for the weekend) and told them do NOT touch it because we cant afford it right now. They said "too late" and that they already started removing the heads. Then today they called me and said that the bill is already up to $1200 just for them sending the heads off. I never told them to do this. They also said i never asked for an oil change and thats not true. Thats the only reason i went there in the first place. Is it legal for them to do this without my consent? sorry its so long.