Where to look for coolant leaks
Pay special attention to the corners, intersections and the position of the hose clamped on the short tube. Signs of expansion mean that the inner reinforcing fabric is damaged and the hose may break at any time. Feeling weak, this also indicates internal damage. Use a flashlight and mirror to look under or behind the hose.
A brown rust deposit on the stubs indicates that the hose may be leaking when under pressure. Tighten the hose clips.
Testing the radiator cap
When you check the coolant level in the radiator, inspect the radiator cap as well.
Make sure the rubber or fiber seal is not damaged and it takes some effort to test the large pressure relief valve by pressing the spring against its spring some effort is needed! Also make sure that the small valves in the center are free to move.
A rough check of the lid is to warm up the engine, wrap the lid with a thick cloth, and then put on the thick gloves to release it to the first stop. Do not remove the cover.
If there is no buzzing of air or steam, the lid may not maintain the correct pressure in the system and should be updated.
Make sure that the new cap has the correct pressure rating, which is marked on it. A pressurised system raises the boiling point of water, but if the valve is too weak the pressure will not be maintained. If it is too strong the system may become over pressurised when the engine is hot.