Water tank reservoir. Porsche 955 / 957 Cayenne 2003-10  ❭  95510614723

Coolant Expansion Tank (Water Tank Reservoir) 

Keep your Porsche Cayenne's cooling system operating efficiently with this OE Match Coolant Expansion Tank (Water Tank Reservoir). Manufactured to  the original factory specification, this direct replacement  provides the correct fit, capacity and connection points for a straightforward installation.

Fits:

• Porsche 955 Cayenne 3.2L V6 2003-06  (D9J Engines)
  
• Porsche 955 Cayenne S 4.5L V8 2003-06  (T90 / T91 Engines)
• Porsche 955 Cayenne Turbo 4.5L 2003-06  (T90 / T91 Engines)
• Porsche 955 Cayenne Turbo S 4.5L 2006>>  (T90 / T91 Engines)
• Porsche 957 Cayenne 3.0L Diesel 2007-10
• Porsche 957 Cayenne 3.6L 2007-10

The expansion tank is a vital part of the engine cooling system, storing coolant as it expands during normal engine operation and returning it to the cooling system as temperatures decrease. Replacing a worn or leaking reservoir helps maintain the correct coolant level, prevents overheating and protects the engine from costly damage.

What Does the Coolant Expansion Tank Do?

The coolant expansion tank performs several essential functions within the engine cooling system.

Its primary roles include:

• Providing a reservoir for expanding engine coolant.
• Maintaining the correct coolant level throughout the cooling system.
• Allowing coolant to return to the radiator and engine as temperatures fall.
• Helping maintain the correct system pressure when used with the pressure cap.
• Assisting with bleeding trapped air from the cooling system.
• Providing a convenient point for checking and topping up coolant.

A correctly functioning expansion tank is essential for maintaining stable engine operating temperatures.

Why Does the Expansion Tank Fail?

Expansion tanks are subjected to constant temperature fluctuations and system pressure, which can eventually weaken the plastic housing.

Common causes of failure include:

• Age-related plastic fatigue.
• Hairline cracks caused by repeated heating and cooling cycles.
• Coolant leaks around hose connections.
• Damage caused by excessive cooling system pressure.
• Discolouration and brittleness from prolonged engine bay heat.
• Internal contamination reducing coolant quality.

A leaking or cracked expansion tank can lead to coolant loss, low system pressure and engine overheating if left unrepaired.

When Should It Be Replaced?

Replacement is recommended when:

• Coolant leaks are visible around the tank.
• The reservoir has become cracked or distorted.
• The plastic has become brittle or heavily discoloured.
• Coolant level warnings occur without any obvious hose leaks.
• The cooling system is being overhauled.
• Replacing other ageing cooling system components during preventative maintenance.

Replacing the expansion tank before it fails can help prevent overheating and reduce the risk of expensive engine repairs.