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Coolant Hoses - Engine Bay
- Porsche 996 C2 3.4L 1997-08/01
Fits:
Porsche 996 C2 3.4L Manual
Kits comes with engine bay rubber pipe
Diagram ref: #1, #3, #18, #23, # 24, #27, #33
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WATERPIPEKIT996C2.34.M
The product you are viewing cross references to these numbers
This kit is comprised of the following items:
- 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 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
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610623356
The product you are viewing cross references to these numbers
- 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
The product you are viewing cross references to these numbers
- 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
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610621260
The product you are viewing cross references to these numbers
- 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
Click 'Zoom in' for large parts diagram.
Diagram ref no 5
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99610672305
The product you are viewing cross references to these numbers
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Radiator coolant hoses are vital conduits within the engine cooling circuit. They transport engine coolant between the engine and radiator, allowing heat absorbed in the engine block to be released via the radiator.
Fits:
Porsche 996 C2 / C4 3.4L 1997 - 2005
Diagram ref no 23
Radiator coolant hose – connects radiator and engine coolant passages as part of the primary cooling loop.
Function:
• Circulates coolant between the engine and radiator
• Helps maintain optimal operating temperatures
• Prevents coolant leaks and pressure loss
• Contributes to engine reliability and longevity
Radiator hoses are continuously exposed to elevated temperatures, pressure fluctuations, and corrosive coolant chemicals. Over time, hoses can weaken, crack, swell, or become brittle, leading to:
• Fluid leaks Engine overheating
• Loss of coolant pressure
• Potential engine damage.
Replacing aged or damaged hoses ensures the cooling system maintains integrity, prevents leaks, and continues to operate as intended by the manufacturer.
Replace this radiator coolant hose if:
• Visible cracking, bulging, or soft spots
• Evidence of coolant seepage or wet residue
• Hoses feel mushy or stiff when squeezed
• During routine coolant service or before long-term storage
• If coolant system overhaul is being performed
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Related, superseded, cross reference or alternative numbers for comparison.
99610650156
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- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01

Fits:
Porsche 996 C2 / C4 3.4L
Click 'Zoom in' for large parts diagram.
Diagram ref no 23
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99610650156
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- Porsche 996 C2 3.4L 1997-08/01
This Porsche Genuine OE Coolant Return Water Hose is a factory-engineered cooling system hose designed for the Porsche 911 (996) Carrera 3.4L models. This molded hose forms part of the engine’s water-cooling circuit and is specifically designed to route coolant through the return section of the system.
Fits:
Porsche 996 C2 3.4L 1998 - 2001 MANUAL
Diagram ref no 3
This product supersedes Porsche's old part numbers: 99610664156, 99610664158.
The coolant return hose carries coolant from the engine return line to the main distribution/return pipe within the cooling system. This circulation allows heated coolant to travel back through the system where it can be cooled and recirculated through the engine.
By maintaining steady coolant flow through the engine’s cooling circuit, the hose helps regulate engine temperature and prevent overheating during both normal driving and high-load conditions.
Functions & Technical Role
• Coolant circulation: Transfers coolant through the return side of the cooling circuit
• Temperature management: Supports stable engine operating temperature
• Pressure tolerance: Built to withstand cooling system pressure and temperature fluctuations
• Flexible connection: Absorbs engine vibration and movement within the cooling system
• OE precision: Molded to Porsche specifications for exact routing and fitment
Fitment / Position on Car:
• Fitting position: Engine cooling system
• Location: Between the engine coolant return line and the main distribution/return pipe
• System: Engine coolant circulation / radiator cooling circuit
Coolant hoses operate under constant heat, pressure, and vibration, which can cause rubber to deteriorate over time. Aging hoses may crack or weaken, increasing the risk of coolant leaks and potential engine overheating. Replacing worn hoses with genuine Porsche OE components helps maintain the reliability and efficiency of the engine cooling system.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610664162
The product you are viewing cross references to these numbers
- Porsche 996 C2 3.4L 1997-08/01
This OE Match coolant return water hose is a cooling system hose designed for Porsche 911 (996) Carrera 3.4L models with manual transmission produced between 1998 and 2001. This hose forms part of the engine’s coolant return circuit, transferring coolant from the engine return pipe to the main cooling system distribution pipe.
Fits:
Porsche 996 C2 3.4L 1998 - 2001 MANUAL
Diagram ref no 3
This product supersedes Porsche's old part numbers: 99610664156, 99610664158.
The coolant return hose allows coolant to flow back through the engine’s cooling circuit after absorbing heat from the engine. This circulation allows the cooling system to maintain stable engine operating temperatures and prevents overheating.
A properly functioning hose ensures uninterrupted coolant flow and supports efficient temperature control.
Function
• Coolant Return Flow: Transfers coolant from the engine return pipe to the cooling system distribution pipe
• Temperature Regulation: Supports the engine thermostat and radiator system
• Cooling System Integrity: Maintains sealed coolant circulation under pressure
• Engine Protection: Helps prevent overheating and coolant leaks
Coolant hoses are constantly exposed to heat, pressure and chemical contact from coolant. Over time the rubber can harden, crack or weaken, increasing the risk of coolant leaks. Replacing ageing hoses helps maintain cooling system reliability and protects the engine from overheating or coolant loss.
When to Replace. Consider replacing the hose when:
• Coolant leaks are visible around hose connections
• The hose shows cracks, swelling or deterioration
• During cooling system overhaul or thermostat service
• As preventative maintenance on higher-mileage engines
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610664162
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- Porsche 996 C2 3.4L 1997-08/01

Fits:
Porsche 996 C2 >>2001
Click 'Zoom in' for large parts diagram.
Diagram ref no 12
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99610613654
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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
Click 'Zoom in' for large parts diagram.
Diagram ref no 5
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610672305
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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 - 1997 to 2005
Porsche 996 turbo - 200 to 2005
Click 'Zoom in' for large parts diagram.
Diagram ref no 10
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99610672706
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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
This Porsche Genuine OE Water Hose is an original factory coolant hose designed for the engine cooling system of Porsche 911 (996) models. This molded hose connects the cooling circuit components around the water thermostat and water pump, allowing coolant to circulate properly through the engine.
Fits:
Porsche 996 C2 / C4 / C4S 1998 - 2005
Diagram ref no 24.
This product supersedes Porsche's old part numbers: 99610650253, 99610650254
The coolant hose transfers engine coolant between the thermostat housing, water pump, and coolant return pipes, helping regulate engine temperature. By maintaining continuous coolant flow through the engine and cooling circuit, it ensures efficient heat dissipation and prevents overheating during normal driving or high engine loads.
The hose’s molded design allows it to fit precisely within the engine bay routing of the 996 cooling system.
Functions & Technical Role
• Coolant circulation: Routes coolant between the thermostat and cooling system pipes
• Temperature regulation: Supports stable engine operating temperature
• Pressure resistance: Designed to withstand cooling system pressure and temperature cycles
• Flexible connection: Absorbs vibration and engine movement within the cooling circuit
• OEM fitment: Molded to Porsche specifications for direct installation
Fitment / Position on Car
• Fitting position: Engine cooling system
• Location: Between the water thermostat housing and water pump / coolant return pipe
• System: Engine coolant circulation system
Coolant hoses operate under constant heat, pressure, and vibration. Over time, rubber can harden or crack, potentially leading to coolant leaks and engine overheating. Replacing worn hoses with genuine Porsche OE components helps maintain proper cooling system performance and prevents costly engine damage.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610650256
The product you are viewing cross references to these numbers
- 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
This OE Match water hose is a coolant hose designed to connect the engine cooling circuit to the water thermostat housing on Porsche 911 (996) models produced between 1998 and 2005. This hose forms part of the engine’s cooling system, allowing coolant to circulate between the engine and thermostat assembly to regulate operating temperature.
Fits:
Porsche 996 C2 / C4 / C4S 1998 - 2005
Diagram ref no 24
This product supersedes Porsche's old part numbers: 99610650253, 99610650254.
The hose carries coolant between the thermostat housing and the engine’s cooling pipes. This allows the thermostat to regulate coolant flow depending on engine temperature, ensuring the engine warms up efficiently and remains within the correct operating range.
A properly functioning coolant hose is essential to maintain stable engine temperatures and prevent overheating.
Function
• Coolant Circulation: Transfers coolant between the thermostat housing and engine cooling pipes
• Temperature Regulation: Supports thermostat operation in controlling engine temperature
• Cooling System Integrity: Maintains sealed coolant flow under pressure
• Engine Protection: Helps prevent overheating and cooling system leaks
Coolant hoses operate under constant heat and pressure. Over time the rubber can become brittle, swell or crack due to thermal cycling and coolant exposure. A deteriorated hose may cause coolant leaks or reduced cooling efficiency, potentially leading to engine overheating. Replacing worn hoses ensures the cooling system maintains proper pressure and flow.
When to Replace. Consider replacing the hose if you notice:
• Visible cracks, swelling or deterioration in the rubber
• Coolant leaks around the thermostat connection
• Loss of coolant pressure or overheating issues
• During cooling system overhaul or thermostat replacement.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610650256
The product you are viewing cross references to these numbers
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
Requires pipe 99610624354
Fits:
Porsche 996 C2 / C4 1998-01 3.4L
This product supersedes Porsche's old part numbers:
- 99610625053
- 99610625054
- 99610625055
- 99610685000
Diagram ref no 18.
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99610685005
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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.