Coolant Hoses - Engine Bay
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Fits:
Porsche 996 C4 3.6L Manual
Kits comes with engine bay rubber pipe
Diagram ref: #1, #3, #18, #23, # 24, #27, #33
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WATERPIPEKIT996C4.36.M
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This kit is comprised of the following items:
- Porsche 996 C4 3.6L 09/01-2005

Fits:
Porsche 996 C4 2002-05
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Diagram ref no 12
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99610683603
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- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 3.6ltr C2 / C4 / C4S - 2002 to 2005
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Diagram ref no 47
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99610685103
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 3.4L/3.6L C2 / C4 / C4S 1998-2005
M 66X 01815 >>
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Diagram ref no 29
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99610623356
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 3.4L/3.6L C2 / C4 / C4S 1998-2005
M 66X 01815 >>
Click 'Zoom in' for large parts diagram.
Diagram ref no 29
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99610623356
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- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 C4 / C4S 1998-05
All-wheel drive (option code: 339)
Click 'Zoom in' for large parts diagram.
Diagram ref no 11
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99610672806
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- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Left Side Return Hose, From right side radiator return pipe to under car return pipe.

Fits:
Porsche 996 C4 / C4S 1998-05
All-wheel drive (option code: 339)
Click 'Zoom in' for large parts diagram.
Diagram ref no 11
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99610672806
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
From feed pipe.

Fits:
Porsche 996 C2 / C4 / C4S 1998-05
Click 'Zoom in' for large parts diagram.
Diagram ref no 27
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99610621260
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
From feed pipe.

Fits:
Porsche 996 C2 / C4 / C4S 1998-05
Click 'Zoom in' for large parts diagram.
Diagram ref no 27
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99610621260
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 996 TURBO 2000-05

Fits:
Porsche 996 Carrera 1998-05
Porsche 996 Turbo 2001-05
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Diagram ref no 5
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99610672305
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- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Hose for long supply tube from engine to short tube going to radiator breather.

Fits:
Porsche 996 C4 / C4S 1998-05
All-wheel drive (option code: 339)
This product supersedes Porsche's old part numbers:
- 99610672403
- 99610672405
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Diagram ref no 6
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99610672406
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- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Hose for long supply tube from engine to short tube going to radiator breather.

Fits:
Porsche 996 C4 / C4S 1998-05
All-wheel drive (option code: 339)
This product supersedes Porsche's old part numbers:
- 99610672403
- 99610672405
Click 'Zoom in' for large parts diagram.
Diagram ref no 6
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99610672406
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- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08

Fits:
Porsche 996 C2 / C4 / C4S- 2002 to 2005
Porsche 997.1 C2 / C4 - 2005 to 2008
Porsche 997.1 C2S / C4S - 2005 to 2008
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Diagram ref no 23
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99710683103
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- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
This coolant hose is engineered to replicate the original Porsche part’s fit, material and function for the cooling system of Porsche 911 (997 series). It connects the engine to the supply pipe, ensuring proper coolant flow and stable engine temperatures under all conditions.
Fits:
Porsche 996 C2 / C4 / C4S 2002 - 2005
Porsche 997.1 C2 / C4 2005 - 2008
Porsche 997.1 C2S / C4S 2005 - 2008
Diagram ref no 23
• Location: Cooling system hose, generally the engine to supply/coolant pipe connection.
• Replacement: for factory numbers 997 106 831 03 and cross-references 996 106 831 01, 997 106 831 02.
• Function: This hose conducts coolant between the engine block and the external supply pipe (or radiator / heat exchanger) as part of the cooling circuit. Correct hose quality and routing are critical to maintaining engine temperature regulation, preventing overheating and avoiding coolant leaks.
Over time, coolant hoses can become hardened, cracked, swollen or leak due to heat cycles, pressure changes and age. A compromised hose may lead to coolant loss, engine overheating, or reduced cooling efficiency.
Replace this hose when:
• The original shows signs of cracks, bulging, oil or coolant staining.
• You notice coolant loss, overheating warnings or low coolant levels.
• You are performing a cooling system overhaul or replacing related pipes/fittings.
Installing this hose restores reliable coolant flow, proper fitment and long-term durability.
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99710683103
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- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 C2/ C4 3.6L
Click 'Zoom in' for large parts diagram.
Diagram ref no 23
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99610683203
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- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005

Fits:
Porsche 996 3.6L C4 AUTO / TIPTRONIC
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Diagram ref no. 3
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99610688809
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Coolant Hoses – Engine Bay | Reliable Cooling for Peak Porsche Performance
Coolant hoses in the engine bay are critical components that circulate coolant between the radiator, water pump, and engine block — maintaining consistent operating temperatures and preventing overheating. These hoses carry coolant through high-pressure, high-temperature zones within the engine bay, ensuring your Porsche performs at its best, even under demanding conditions.
At Design911, we stock a wide range of genuine and manufacturer-quality engine bay coolant hoses for Porsche models including 911, Boxster, Cayman. Each hose is designed to fit perfectly, resist extreme temperatures, and deliver long-lasting performance — matching the quality, precision and reliability.
What Do Engine Bay Coolant Hoses Do?
Coolant hoses form part of your Porsche’s closed-loop
cooling system. Their job is to:
- Circulate
coolant between the engine, radiator, and water pump.
- Maintain
engine temperature for optimal performance and emissions.
- Support
consistent coolant pressure during operation.
- Prevent engine overheating and protect internal components from heat damage.
In high-performance engines, such as those found in Porsche vehicles, properly functioning hoses are essential for ensuring precise temperature control and long-term mechanical integrity.
Why Do Engine Bay Coolant Hoses Fail?
Over time, coolant hoses endure constant exposure to heat,
vibration, and pressure, which can cause wear and eventual failure. Common
causes include:
- Rubber
deterioration from heat cycling and coolant chemicals.
- Cracking
or hardening due to age and environmental factors.
- Swelling
or soft spots from internal coolant corrosion.
- Leaks
at connections caused by weakened hose ends or clamps.
- Abrasion or rubbing against other engine components.
Symptoms of failure include coolant leaks, overheating, fluctuating temperature readings, or a noticeable smell of coolant in the engine bay.
Why Replace Faulty Coolant Hoses?
A damaged or leaking hose can cause rapid coolant loss and severe engine overheating. Replacing worn hoses ensures your Porsche’s cooling system functions reliably and efficiently.
Benefits of replacement include:
- Restored coolant circulation and temperature control.
- Prevention of leaks, overheating, and potential engine damage.
- Improved reliability and performance under all driving conditions.
- Manufacturer-quality construction and perfect fitment.
All hoses in this range are built using reinforced, high-grade rubber compounds designed to withstand extreme heat, pressure, and vibration — ensuring lasting durability and peace of mind.