Expansion Tank Hoses
Renew the coolant overflow connection on your Porsche Boxster with this genuine OEM overflow hose. Designed for the Boxster 1997-2008, this main fill/overflow hose links the cooling system to the expansion reservoir, ensuring proper coolant expansion, return flow and system pressure stability.
Fits:
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005 -08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
Diagram Ref No 29
What This Product Does:
- This hose functions as the connection between the cooling system (likely radiator or coolant header) and the overflow/expansion reservoir. When coolant expands under heat or pressure, surplus fluid flows into the reservoir; conversely when the system cools, fluid returns.
- Ensures that cooling system overflow is safely directed, that the reservoir receives the fluid, and that the cooling circuit maintains correct pressure, volume and recirculation.
- Proper operation helps avoid coolant loss, maintain correct cooling system levels, and helps prevent boil-over or overheating due to un-controlled coolant expansion.
Symptoms Of Wear Or When To Replace:
- Coolant leakage around the reservoir, hose clamps, or along the path of the overflow hose — e.g., dripping coolant, crusty residue near joints.
- Overheating or low coolant, where the expansion reservoir remains dry, suggesting the hose isn’t delivering returning fluid or has collapsed.
- Burst, cracked or hardened hose— rubber hoses degrade with heat/age, causing soft spots, bulges, cracks or collapse under pressure.
- Hose slack or loose clamps— if the hose is long out of service it might sag, the ends may be brittle, or clamps may be corroded leading to poor seal.
- If the vehicle is running very hot or the coolant level drops unexpectedly, and checks show the overflow system not functioning properly.
- On older Boxsters many cooling-system hoses are aged and replacement is preventive maintenance.
Why Replacement Matters:
- Maintains cooling system integrity: A faulty overflow hose can lead to coolant loss, pressure escape or improper reservoir return—affecting system performance and engine cooling.
- Prevents overheating or coolant loss: Since the hose handles expansion flows, failure can result in overflow at wrong points or low reservoir levels, which may lead to engine overheating or damage.
- Reliability and longevity: Rubber coolant hoses degrade over time due to heat, vibration and pressure cycles — replacing them restores system reliability.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610626703
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005 -08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
Shop Securely
12 Month Warranty
Worldwide Delivery
Expansion Tank Coolant Hoses – Reliable Cooling Connections for Porsche Vehicles
Expansion tank coolant hoses are essential components in your Porsche’s cooling system. They connect the coolant expansion tank (reservoir) to the radiator, water pump, and engine, allowing the system to maintain correct pressure and coolant levels during operation. These hoses ensure that excess coolant flows smoothly between the tank and the rest of the system — preventing overheating, leaks, and pressure loss.
At Design911, we supply a full range of genuine and manufacturer-quality expansion tank coolant hoses for Porsche models including 911, Boxster, Cayman, Cayenne, Macan, and Panamera. Each hose is engineered for precise fitment, heat resistance, and long-term durability, ensuring your Porsche’s cooling system performs exactly as intended by the manufacturer.
What Do Expansion Tank Coolant Hoses Do?
Expansion tank hoses act as the link between the coolant
reservoir and the engine cooling circuit, helping to:
- Transport
coolant to and from the expansion tank as temperatures fluctuate.
- Maintain
proper pressure balance within the cooling system.
- Allow
coolant recovery as the system heats up and cools down.
- Prevent air pockets that can cause inefficient cooling or engine overheating.
Without properly functioning hoses, the cooling system cannot maintain the balance of pressure and temperature required for optimal performance.
Why Do Expansion Tank Coolant Hoses Fail?
Due to constant exposure to heat, pressure, and coolant
chemicals, these hoses can degrade or fail over time. Common causes include:
- Rubber
fatigue or cracking from repeated heat cycles.
- Coolant
leaks caused by weakened hose ends or clamps.
- Swelling
or softening from prolonged coolant contact.
- Aging
materials losing elasticity and sealing ability.
- Corrosion or contamination around connectors and fittings.
Typical signs of failure include visible cracks, coolant leaks near the expansion tank, fluctuating coolant levels, or overheating warnings.
Why Replace Faulty Expansion Tank Coolant Hoses?
A damaged or leaking expansion tank hose can cause coolant loss, air pockets, or pressure imbalance, leading to overheating or potential engine damage. Replacing these hoses is a simple but critical maintenance step to keep your Porsche’s cooling system running reliably.
Benefits of replacement include:
- Restored coolant flow and pressure regulation.
- Prevention of leaks and air ingress.
- Enhanced engine performance and temperature stability.
- Long-lasting, manufacturer-quality durability and fitment.
All hoses in this range are made using high-grade, reinforced materials designed to meet or exceed factory standards, ensuring exceptional performance, heat resistance, and reliability under all driving conditions.
