Q: Overheating engine

If the vehicle is presently overheating, you want to check, and perhaps just replace, the cooling system thermostat (thermostats are not costly and they do eventually fail), check the radiator for blockages (radiators can be flow tested) and check the water pump to make sure it is actually turning at engine speed (i.e., is the drive belt properly tensioned?). Overheating, if severe enough, can lead to leaks at the cylinder head gasket. If you are seeing white smoke in the exhaust, that could indicate a head gasket leak. Check the engine oil to see if there is any evidence of water/antifreeze contamination. Other possible causes of engine overheating are a malfunctioning radiator (and/or a/c condenser) electric cooling fan, radiator obstructions (external), dragging brakes, and engine operating conditions such as retarded ignition timing, or excessively lean fuel air ratio. If a deteriorated coolant hose has been detected, and you can see evidence of the deterioration as pointed out by the mechanic, you should get that replaced. As far as the small leak, as leaks are repaired in a sealed system, pressure is restored to the normal, "design" level. As such, additional places could leak, even as they were not leaking before, simply because design pressure is restored throughout the system and that may very well explain the belated appearance of the small leak. The thing to do at this point is make sure the smoke doesn’t represent loss of coolant through the head gasket into the combustion chamber. If it does, the head gasket has to be replaced prior to any other repairs such as replacement of the thermostat. If YourMechanic serves your region, a certified professional from YourMechanic can diagnose the cause(s) of your engine overheating and let you know of the required repairs. Please let us know how we can further assist you.