Several things can cause this. If there is no visible leak, then the fan may be broken, the water pump is knackered. Water pumps generally emit a high pitched noise which is hard to miss when they are on their way out. A blockage in the radiator or possibly a bad thermostat could also cause it. Worst case is your head gasket is blown which means coolant is getting into your motor, you'd be able to tell however because you'd see clouds of smoke in your rear view mirror when driving. As long as it's not the latter, should be a pretty cheap fix, I'd get in touch with your mechanic if the problem has started since coming back from the garage.

See if the elec fans are spinning, change the thermostat, flush the system then replace the coolant if it is more than 2 years old. Bypass the heater core to see if that is corrode and blocked.

if the engine got hot its probably too late for it as the head is probably warped. if so its a throw away and you will have to get another engine. know this as you take the beast back to the mechanic that is responsible..............

All of the answers are WRONG. Take the car back to the mechanic. THAT is the right answer. WHY ASK HERE? No need to reach for the smartphone. NOT SMART. Go to the mechanic.

It could be that your thermostat is stuck shut. Locate where it is, remove it and stick it in a pot of hot water, just below boiling. If it doesn't open, it is bad. This means that the coolant is not circulating through your engine. Get another one.

definatly check the thermo

I took my car to the mechanic 2 days ago now I'm on the way and suddenly I have a warming that engine temperature is too hot so I pull over n open the hood the engine is really hot there's no leak there's coolant in it I shut the car off for 15 mns it cool back down to normal soon I start driving again it get hot slowly any ideas