First, where is it leaking. If you smell coolant inside the car, the windows mist up with a "slimy" film, or the front carpet/floorboards are wet, you likely have a bad heater core-the "mini-radiator" under the dash that provides heat and defrost. Does the car leave green puddles where it is parked? It could be leaking from the radiator, hoses, or water pump-you have to look for green (or orange, depending on the type of coolant used) drops or dried residue-a healthy car should have none. If there are no drips or puddles, the car could be leaking coolant into the cylinders via a leaking head gasket. Usually this is accompanied by poor performance and white "puffing" from the tailpipe when the engine idles. Another common cause is a bad radiator cap, if the coolant bottle shows signs of cooland coming out of the overflow drain, a cap with a weak spring could be allowing coolant out of the engine when it shouldn''t. Finally, ensure the engine isn't overheating, as this can cause the overflow condition just mentioned.
Any coolant leak can cause an overheat.Any coolant leak can cause an overheat.
you have to find where the leak is first.
No.
Leak in heater core
a leak in a head gasket could cause coolant to go into only one cylinder.
The leak could come from: hoses, punctured radiator, split gasket...you can put tracer dye in the coolant and search for the leak with a black light after you clean the engine.
A low coolant level could cause the temp gauge not to read correctly. A faulty temp gauge sending unit could also be the cause. The coolant leak, you would have to find the source of the leak to determine the cause.
Blown head gasket
You have a coolant leak.You have a coolant leak.
If a coolant leak were caused by brake work, I'd never have that person work on my brakes - ever. Just the brakes, I would think it highly unlikely that it would result in a coolant leak. If they were replacing the master cylinder, then I could see a possibility of someone inadvertently causing a coolant leak, but that would still even be a stretch.
You'll lose coolant.
Could be an A/C coolant leak.