Best way to check for leak or overheating problem is with Leak Detector . The best way to do this is with a pressure tester.

This tool pressurizes the cooling system and forces the coolant to leak if there is a place for it to escape. Often you can find those pesky small leaks that are difficult to spot with this method.  Another method is to just put your eyes on the engine and surrounding area. Often when coolant leaks, it leaves a nice stain around the area where it leaks, which can be easy to spot if you’re lucky. Once you’ve found the leak, repair it, bleed the system, and recheck for the overheat condition.

If you don’t find any external leaks, it’s time to get creative. Also, don’t forget to check under the dash for coolant leaks when pressure testing. A leaking heater core can cause this, and since it’s buried in the HVAC system, it can be hard to spot a leak from this area. If you notice wet carpet on the passenger-side floorboard, or your windshield fogs up and is perhaps coated with a greasy residue, you could have a heater core failure.

You can leaks in the following : Head gasket;

Header tank;
Radiator and heater cores;
Water pump, plugs, hoses and housings.

Garutech 08023190606