If water suddenly and dramatically comes out of the radiator reservoir when the engine is cold, there may be several possible causes for this problem:
1. **Leak in the radiator hose or pipes**: There may be a leak in one of the hoses connected to the radiator or in the coolant pipe, which causes water to come out when the system is cold and its pressure is low.
2. **Leakage in the radiator tank itself**: The tank may have a crack or a small hole that allows water to escape.
3. **Excess air pressure in the system**: If there is excess air pressure in the system, it may cause water to be forced out of the radiator when the engine cools.
4. **Cooling (Centrifugal) Valve**: If the radiator's cooling valve is ineffective, it may not be able to properly retain water in the system.
To check the exact cause, you can do the following steps:
- Ensure that there are no visible leaks in the hoses or pipes.
- Check the radiator tank to ensure that there are no cracks or holes.
- Ensure that the coolant level in the radiator is appropriate.
- Check the cooling valve to ensure it is working properly.
If you cannot identify the problem yourself, it is best to consult a professional mechanic to conduct a comprehensive inspection of the cooling system and accurately diagnose the problem.
