Radiator Cap 1.1 bar (Genuine) EVO4-9

Genuine Mitsubishi radiator cap (part number 1350A730) rated at 1.1 bar, designed for EVO 4–9. This cap maintains the correct cooling system pressure, ensuring optimal engine temperature and preventing coolant boil-over.

One of the main signs that a radiator cap is not holding pressure is when the coolant overflow bottle keeps filling up (and sometimes even spilling over).

Here’s why:

• The radiator cap is designed to hold pressure up to its rating (e.g., 1.1 bar / 16 psi).

• If the cap is weak or its seal is damaged, it will release coolant too early.

• Instead of keeping pressure in the radiator, it lets coolant flow into the overflow bottle even when the system isn’t overheating.

• As a result, the overflow bottle becomes overfilled, while the radiator itself may end up low on coolant.

Other symptoms of a failing radiator cap include:

• Coolant loss with no visible leaks

• Engine running hotter than normal

• Collapsed radiator hoses after cooling down (from vacuum not being regulated properly)

👉 If your overflow bottle is constantly filling up, replacing the radiator cap is usually the first (and cheapest) fix to try.