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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Related, superseded, cross reference or alternative numbers for comparison.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
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
Genuine Porsche Original Equipment (OE) heater coolant return hose that connects between the engine cooling circuit and the heater return line, ensuring proper coolant flow through the heater core and back to the engine cooling system.
Fits:
Porsche 996 Carrera 2002 - 2005 Tiptronic Gearbox only
Porsche 997.1 3.6L / 3.8L 2004 - 2008
Porsche 997.1 Turbo / GT2 2007 - 2009
Porsche 997.2 Turbo / GT2 RS 2010 - 2013
Porsche 997 GT3 3.8 / 4.0 2009 - 2011
Diagram ref no 42
This hose ensures an unobstructed and secure channel for coolant returning from the vehicle’s heater core to the engine cooling loop, playing a vital role in passenger cabin heating and overall engine thermal regulation. Its precise fit and correct routing are essential to avoid bypassing or pinching, which could otherwise lead to heater inefficiency or premature failure.
Installed between the heater core outlet and the engine’s return fitting, this hose:
• Transports heated coolant from the heater core back to the engine cooling system
• Maintains correct flow and pressure balance within the cooling circuit
• Operates under high temperatures and multiple thermal cycles
• Interfaces with factory-specified clamps and hose connections
Because it is made to OE specification, the hose ensures proper sealing and routing that matches the original Porsche design.
A cooling system hose that has become brittle, cracked, swollen, or porous can leak or restrict flow, leading to reduced heating performance, coolant loss, and potential engine overheating. Because the heater return hose carries pressurised coolant across temperature extremes, degradation over time is typical. Replacing it with a Genuine Porsche OE part ensures correct material performance and sealing, helping preserve cooling efficiency and prevent unexpected failures.
When to replace:
• Visible cracks, swelling, or soft spots
• Coolant leaks around the hose ends
• Heater blowing cold air, indicating poor coolant flow
• Cooling system overhaul or heater core service
• Preventive maintenance on high-mile vehicles
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622275
The product you are viewing cross references to these numbers
- 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
- Porsche 997 MK1 TURBO 2007-09
- Porsche 997 MK1 GT3 2007-09
- Porsche 997 MK1 GT2 2007-09
- Porsche 997 MKII GT3 2010-11
- Porsche 997 MKII Turbo 2010-13
- Porsche 997 MKII GT2 RS 2011-13
OE Match heater coolant return hose is a direct-fit replacement designed to replicate the original Porsche hose used in the heater return circuit on Porsche 911 996 and 997 models. It carries coolant from the heater core back into the engine cooling system, supporting both cabin heating and overall thermal regulation.
Fits:
Porsche 996 Carrera 2002 - 2005 Tiptronic Gearbox only
Porsche 997.1 3.6L / 3.8L 2004 - 2008
Porsche 997.1 Turbo / GT2 2007 - 2009
Porsche 997.2 Turbo / GT2 RS 2010 - 2013
Porsche 997 GT3 3.8 / 4.0 2009 - 2011
Diagram ref no 42
The hose installs directly using original mounting points and standard Porsche hose clamps, making it suitable for both routine maintenance and larger cooling system overhauls.
The heater coolant return hose channels warmed coolant from the heater core back to the engine’s cooling circuit, completing the heater loop. This allows the cooling system to maintain balanced flow and ensures consistent interior heating performance.
Installed between the heater core outlet and the engine return line, this hose:
• Maintains correct coolant flow and pressure in the heater circuit
• Supports reliable cabin heating
• Resists collapse, swelling, and heat degradation
• Integrates with factory hose routing and connections
Its OE-matched geometry ensures proper clearance and reduces stress on joints and adjacent hoses.
Over time, heater hoses deteriorate due to heat cycling and coolant exposure. A failing return hose can cause coolant leaks, reduced heating efficiency, air ingress into the cooling system, or engine overheating. Replacing worn hoses with an OE Match component restores proper coolant circulation and helps prevent unexpected cooling system failures.
When to replace:
• Visible cracks, swelling, or soft spots
• Coolant leaks around the hose ends
• Heater blowing cold air, indicating poor coolant flow
• Cooling system overhaul or heater core service
• Preventive maintenance on high-mile vehicles
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622275
The product you are viewing cross references to these numbers
- 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
- Porsche 997 MK1 TURBO 2007-09
- Porsche 997 MK1 GT3 2007-09
- Porsche 997 MK1 GT2 2007-09
- Porsche 997 MKII GT3 2010-11
- Porsche 997 MKII Turbo 2010-13
- Porsche 997 MKII GT2 RS 2011-13

Fits:
Porsche 996 - 1997 to 2005
Porsche 996 turbo - 200 to 2005
Click 'Zoom in' for large parts diagram.
Diagram ref no 10
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610672706
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 - 2002 onwards
For engine codes - M96-10, M96-02, M96-04, M96-03
Click 'Zoom in' for large parts diagram.
Diagram ref no 24
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610683204
The product you are viewing cross references to these numbers
- 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 - 2002 onwards
For engine codes - M96-10, M96-02, M96-04, M96-03
Click 'Zoom in' for large parts diagram.
Diagram ref no 24
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610683204
The product you are viewing cross references to these numbers
- 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 / C4S 1998-05
This product supersedes Porsche's old part numbers:
- 99610650253
- 99610650254
Click 'Zoom in' to see the diagram.
Diagram ref no 24.
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

Fits:
Porsche 996 C2 / C4 / C4S 1998-05
This product supersedes Porsche's old part numbers:
- 99610650253
- 99610650254
Click 'Zoom in' to see the diagram.
Diagram ref no 24.
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

Fits:
Porsche 996 C2 / C4 / C4S 2002-05 3.6L
It's recommended to buy pipe 99610685103 along with this part.
This product supersedes Porsche's old part numbers:
- 99610685001
- 99610685005
Click 'Zoom in' to see the diagram.
Diagram ref no 18.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610685006
The product you are viewing cross references to these numbers
- 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 / C4S 1998-05 Tiptronic Gearbox
Click 'Zoom in' to see the diagram.
Diagram ref no 33.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622266
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

Fits:
Porsche 996 C2 / C4 / C4S 1998-05 Tiptronic Gearbox
Click 'Zoom in' to see the diagram.
Diagram ref no 33.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622266
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

Fits:
Porsche 996 C2 / C4 3.6L Manual Gearbox
Click "Zoom in" to see the diagram.
Diagram ref no 33.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610622267
The product you are viewing cross references to these numbers
- 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 Carrera 2/4 3.4L 1997>>2001
Porsche 996 Carrera 2/4 3.6L 2001>>2005
Porsche 996 Carrera 4S 3.6L 2001>>2005
Diagram Ref No 29
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610623351
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

Fits:
Porsche 996 C4 / C4S 1997-05
Click 'Zoom in' for large parts diagram.
Diagram ref no 8
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610672002
The product you are viewing cross references to these numbers
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
M 66X 01815

Fits:
Porsche 996 Carrera 3.4L / 3.6L 2001>>
6-speed manual transmission
Click 'Zoom in' for large parts diagram.
Diagram ref no 26
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99610624255
The product you are viewing cross references to these numbers
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
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.