Aluminium Radiators & Engineering Pty Ltd
Unit 11 / 60 Kremzow Rd
Brendale QLD Australia

Ph +61 07 32054620 Email

The Importance of the Radiator Cap

Tridon radiator caps are manufactured in ISO9002 accredited
factories and are designed and manufactured to perform as well
as the original equipment radiator cap. Tridon style radiator caps
are in common use both in Europe and North America and suit a
very wide range of vehicle applications.
All Tridon radiator caps are the ~ style and are
suitable for use on both coolant recovery systems and non coolant
recovery systems.
A coolant re over stem has an overflow bottle attached to the
radiator and allows a two-way flow of coolant. By allowing coolant
to return to the radiator there is no opportunity for air to enter the
cooling system and the surface area of the radiator in contact with
coolant is also always maintained at the maximum area possible.
 A ~tem has no bottle and can only allow the release
 of coolant to the atmosphere and the return of air into the radiator.
 Non recovery systems are therefore, not as efficient as recovery
 Cooling system performance improves when using a recovery
 style cap on a non-coolant recovery system due to more uniform
 cooling system pressurisation occurring.
 The Tridon radiator cap raises and regulates the pressure within
 the cooling system by using both pressure and vacuum operated
 valves. This pressure results in a higher coolant boiling point.
 The raised coolant boiling point provides an increased safety
 margin between the opening temperature of the thermostat and
 the boiling point of the coolant. As a result, the complete cooling
 system operates more efficiently.
 In the normal position both the pressure and vacuum valves of
 the Tridon cap remain closed (Figure 1 ). The pressure in the
 cooling system rises as the temperature rises. When the pressure
 begins to exceed the rated pressure the pressure valve opens
 (Figure 2) releasing pressurised coolant from the radiator.
 The pressure valve closes as the excess cooling system pressure
 reduces. The cycle of opening and closing the pressure valve
 continues, maintaining the appropriate system pressure and
 protecting cooling system components from exposure to excessive
 cooling system pressure.
  The cooling system pressure reduces when the system cools down
  and the coolant contracts. A negative cooling system pressure
  will develop unless there is a way for the pressure in the system
  to equalise. This negative pressure can cause radiator tanks and
  hoses to collapse causing expensive damage to the cooling
  To prevent this damage the Tridon radiator cap has an additional
  vacuum valve that allows coolant or air to return to the radiator
  as the pressure reduces (Figure 3). This serves a dual purpose
  nf allowino the coolin_ci sVstem pressure to equalise as well as



Tridon Australia Pty Ltd (1998) Master Catalogue:Thermostats, Radiator Caps, Thermo Fan Switches & Gaskets, 4th Ed.,

Aluminium Radiators and Engineering Pty Ltd (ARE Cooling)
 While every effort is made to ensure details and information is correct at time of publishing Sunday, 05 August 2012
please contact ARE by phone, fax or email to confirm prices before order