Engineered to Maintain Cooling System Pressure

Often overlooked but critical to cooling system performance, the radiator cap plays a vital role in maintaining the correct operating pressure within the cooling system. By regulating pressure and controlling coolant flow between the radiator and expansion tank, the radiator cap helps raise the coolant's boiling point, improve cooling efficiency and protect the system from damage.

Manufactured to rigorous quality standards and engineered for reliable sealing performance, Serck radiator caps are designed to maintain precise pressure levels throughout the cooling system. Available in a wide range of pressure ratings and fitments, the range provides dependable replacement solutions for modern passenger cars, light commercial vehicles and specialist applications.

Serck Radiator Cap 44

StockASSIST: Our Most Popular Radiator Caps for the UK Aftermarket

Radiator caps may be small components, but they are frequently replaced due to wear, loss or cooling system repairs. Their low cost and broad vehicle coverage make them an important stock line for factors supporting both modern and ageing vehicle parc.
StockASSIST helps identify the radiator cap applications most commonly required by UK workshops, ensuring the right products are available when customers need them.

Serck Radiator Cap 44

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Serck Radiator Cap

Serck Radiator Cap 26

CCC0026

Serck Radiator Cap

Serck Radiator Cap 13

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Serck Radiator Cap

Serck Radiator Cap 6

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Serck Radiator Cap

Serck Radiator Cap 7

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Serck Radiator Cap

Serck Radiator Cap 31

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Serck Radiator Cap

Serck Radiator Cap 72

CCC0072

Serck Radiator Cap

Serck Radiator Cap 33

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Serck Radiator Cap

Serck Radiator Cap 65

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Serck Radiator Cap

Serck Radiator Cap 59

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Serck Radiator Cap

TechASSIST: Product Support and Information

The radiator cap performs several important functions within the cooling system. It: • Maintains the correct cooling system pressure • Raises the coolant boiling point for improved cooling performance • Prevents coolant loss during normal operation • Controls coolant flow between the radiator and expansion tank • Protects hoses, seals and cooling system components from excessive pressure • Helps ensure stable engine operating temperatures Although simple in appearance, a faulty radiator cap can cause a range of cooling system issues and should always be considered during cooling system diagnosis.

Why Do They Fail?

Radiator caps operate in a demanding environment and can deteriorate over time due to:

  • Seal hardening caused by age and heat exposure
  • Spring fatigue reducing pressure retention capability
  • Corrosion from contaminated or degraded coolant
  • Physical damage from incorrect removal or installation
  • Wear to locking tabs and sealing surfaces
  • General ageing of rubber sealing components

Lost or missing caps are also a surprisingly common cause of cooling system issues.

Symptoms of a Failing Radiator Cap

  • Coolant loss without obvious leaks
  • Engine overheating during normal operation
  • Coolant overflowing from the expansion tank
  • Collapsed radiator hoses after cooling down
  • Low coolant warning lights or frequent top-ups required
  • Visible coolant staining around the cap or filler neck
  • Pressure test failures during cooling system diagnosis

Fitting Tips

  • Always match the replacement cap to the vehicle manufacturer's specified pressure rating
  • Inspect the filler neck for corrosion, damage or contamination before installation
  • Check hoses and expansion tanks for signs of excessive pressure or previous overheating
  • Never fit a higher-pressure cap than specified by the vehicle manufacturer
  • Replace damaged seals immediately to prevent coolant loss
  • Following installation, run the engine to operating temperature and check for leaks