Motorad Caps

~MotoRad Caps Product Line~

December 8, 2021
min read

Motorad Caps

MotoRad’s radiator and expansion tank caps range contain 50-part numbers that will fit perfectly to your vehicle. All radiator and expansion tank caps might look similar, but they are different in features, size shape, and the material they are made of. They play a very significant role as a vital part of the vehicle cooling system

MotoRad developed the radiator and expansion tank caps range to comply with the strictest OEM specifications. MotoRad is the expert in the cooling system, and we recommend to always refer the vehicle application list
to ensure the correct part number was picked.

How does it work?

The car’s radiator is a heat exchanger, transferring excess heat from the engine’s coolant fluid into the air. The radiator is composed of tubes that carry the coolant fluid, a Radiator protective cap that is also a pressure valve, and a tank on each side to catch the coolant fluid overflow.

When coolant fluid overheats, it expands, causing the fluid to become highly pressurized. The coolant enters the radiator, the pressure increases even more because it’s in an enclosed space. The radiator cap acts
as a release valve set to open at the maximum pressure point.

The seal provided by the cap ensures a consistent pressure level and secures control when the pressure increases as the coolant heat up and expands. As the temperature lowers the coolant returns to the recovery tank.  Without a functioning radiator cap, the engine can overheat at lower temperatures and the coolant will not return to cool it off.


Pressurized caps

  • As the engine warms  and the system pressure reaches the caps rated pressure, the pressure spring compresses, and pressurized  coolant flows into the reservoir or coolant overflow  tank – it allows the expansion of the heated fluid
  • The radiator cap also allows the coolant to flow back into the radiator as the engine cools
  • As the temperature drops and the coolant contracts, a vacuum is created in the engine’s cooling system
  • The vacuum valve opens and allows the coolant to flow from the overflow tank back to the radiator



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