Power Steering Pipes / Hoses / Radiators

Power Steering Return Line, LHD.
The Genuine Porsche Power Steering Return Line 99634744911 is a replacement hydraulic line for the power-assisted steering system on compatible left-hand-drive (LHD) Porsche vehicles.

Fits:

• Porsche Boxster 986 2.7L 2002
• Porsche Boxster S 986 3.2L 2002
• Porsche Boxster 986 2.7L 2003-04
• Porsche Boxster S 986 3.2L 2003-04
• Porsche 996 C2 3.6L 02-2005
• Porsche 996 C4 3.6L 09/01-2005
• Porsche 996 C4S 3.6L 02-2005
• Porsche 996 GT2 2002-05
• Porsche 996 GT3 MKI 2002
• Porsche 996 GT3 MKII 2003>>  

Diagram Ref No 2

The return line carries power steering fluid back through the hydraulic system after it has assisted steering operation. Maintaining a sealed and unrestricted return path is essential for correct fluid circulation, consistent steering assistance and protection of the power steering pump and associated components.

As a Genuine Porsche component, this line is manufactured for the intended factory installation and is suitable for replacing an original return line that has become cracked, leaking, corroded or otherwise damaged.

What This Product Does:
A hydraulic power steering system uses pressurised fluid to reduce the amount of effort required to turn the steering wheel.

The power steering pump circulates hydraulic fluid through the system. After the fluid has performed its steering-assistance function, it must return through the system so that it can be recirculated.

The power steering return line provides this return path.

Its functions include:

• Returning hydraulic fluid through the power steering system
• Maintaining continuous power steering fluid circulation
• Helping maintain correct hydraulic system operation
• Preventing fluid from escaping from the system
• Supporting consistent steering assistance
• Helping protect the power steering pump from low-fluid operation

Although the return side generally operates at lower pressure than the main pressure supply line, it must still remain properly sealed and free from restrictions.

Symptoms Of Wear Or Failure:
Power steering lines are exposed to heat, vibration, hydraulic fluid, road contamination and ageing.

Over time, deterioration can result in leaks or restricted fluid flow.

Common symptoms include:

• Power steering fluid underneath the vehicle
• Visible fluid around the return line
• Damp or oily hose connections
• Falling power steering fluid level
• Frequent need to top up the reservoir
• Heavier steering effortIntermittent power steering assistance
  
• Whining or groaning from the power steering pump
• Foaming or aeration in the fluid reservoir
• Burning smell if fluid reaches hot components
• Visible cracking or deterioration of flexible hose sections
• Corrosion on metal sections or fittings
• Damaged or loose connections

Any unexplained loss of power steering fluid should be investigated promptly.

Why Replacement Matters:
The return line is essential for maintaining a sealed and correctly circulating hydraulic power steering system.

Replacing a damaged or leaking line helps:

• Stop power steering fluid loss
• Restore correct hydraulic fluid circulation
• Maintain consistent steering assistance
• Reduce the risk of air entering the system
• Protect the power steering pump
• Prevent fluid contamination of surrounding components
• Restore the reliability of the steering system

Because steering is a safety-critical vehicle system, known hydraulic leaks or damaged lines should be repaired promptly.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99634744911

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Power Steering Return Line, Rear. 

The Genuine Porsche Rear Power Steering Return Line (Part Number: 99634744103) is an original equipment hydraulic steering component designed for selected Porsche 911 (996) models manufactured from the 2002 model year onwards.

Fits:

• Porsche 996 C2 3.6L 2002-2005
• Porsche 996 C4 3.6L 2002-2005
• Porsche 996 C4S 3.6L 2002-2005  

Diagram Ref No 9

Manufactured to Porsche's original equipment specifications, this return line forms part of the hydraulic power steering system, providing a passage for power steering fluid to return through the system after assisting the steering mechanism.

Located towards the rear of the vehicle, the pipe forms part of the connection arrangement associated with the engine-driven power steering pump and the fluid return circuit.

The Porsche 996 uses a hydraulic power steering system to reduce the effort required to turn the steering wheel. During operation, the power steering pump circulates hydraulic fluid through the steering system, providing assistance as the driver turns the wheel.

After passing through the hydraulic steering circuit, fluid returns towards the pump and reservoir arrangement. The rear return line helps complete this circulation path.

Correct fluid circulation is essential for maintaining consistent steering assistance, protecting the pump and preventing unnecessary wear to hydraulic system components.

Over time, the original return line may deteriorate due to repeated heat exposure, vibration, corrosion, ageing seals or physical damage. Damaged fittings or pipework can allow hydraulic fluid to escape, potentially reducing the fluid level and affecting the operation of the power steering system.

A leaking or restricted return line may contribute to steering pump noise, fluid loss or inconsistent steering assistance.

Replacing a damaged or leaking rear power steering return line with a Genuine Porsche component helps restore the integrity of the hydraulic circuit, maintain reliable fluid circulation and protect the steering system from avoidable damage.

Ideal for power steering leak repairs, hydraulic system maintenance, engine removal work and specialist Porsche restoration projects, this Genuine Porsche return line provides a factory-specified replacement for compatible Porsche 996 models.

What This Product Does:
The rear power steering return line is an important component of the Porsche 996 hydraulic steering system.

Its primary function is to carry hydraulic fluid through the low-pressure return side of the power steering circuit.

When the engine is running, the power steering pump supplies pressurised fluid to the steering rack. Hydraulic pressure assists the movement of the steering mechanism, reducing the physical effort required from the driver.

After the fluid has passed through the steering system, it returns through the appropriate return pipes towards the pump and reservoir circuit.

The rear return line provides part of this route near the engine and pump assembly.

Its main functions include:

• Returning power steering fluid: Provides a passage for hydraulic fluid travelling back through the steering circuit.
• Supporting continuous fluid circulation: Helps maintain the flow of fluid required for normal power steering operation.
• Maintaining hydraulic system integrity: Provides a sealed connection between the relevant return circuit components.
• Preventing fluid loss: Correctly fitted pipework and seals help contain power steering fluid.
• Supporting consistent steering assistance: Helps maintain the hydraulic fluid supply needed for dependable steering operation.
• Protecting the power steering pump: Supports the fluid circulation conditions required for normal pump operation.
• Maintaining correct fluid routing: Preserves the original rear power steering pipe configuration.
• Reducing contamination risks: Secure connections help prevent external contaminants entering the hydraulic circuit.
• Preserving factory functionality: Maintains Porsche's intended hydraulic steering arrangement.

Symptoms Of Wear Or Failure:
The rear power steering return line is exposed to engine compartment temperatures, hydraulic fluid, vibration and repeated thermal cycling.

Although designed for durability, the pipework and associated connections may deteriorate over time.

Common symptoms of a worn or damaged power steering return line include:

• Visible power steering fluid leaks: Damaged pipework or deteriorated connections may allow hydraulic fluid to escape.
• Fluid stains beneath the vehicle: Leaking fluid may leave visible patches on the ground.
• Oil residue around the rear engine area: Dampness near the return line or its connections may indicate hydraulic fluid seepage.
• Falling power steering fluid level: Continued leakage may cause the reservoir level to decrease.
• Power steering pump whining: Low fluid levels may allow air to enter the hydraulic system, causing pump noise.
• Increased steering effort: Significant fluid loss may reduce available hydraulic steering assistance.
• Intermittent steering assistance: Severe fluid loss or air contamination can contribute to inconsistent steering operation.
• Foaming or aerated fluid: Air entering the system may cause bubbles or foam to appear in the reservoir.
• Visible corrosion: Environmental exposure may weaken metal sections of the return line or its fittings.
• Cracked or damaged hose sections: Where flexible sections are incorporated, ageing and heat may cause deterioration.
• Loose or damaged hydraulic fittings: Worn connections may prevent secure sealing.
• Kinked or crushed pipework: Incorrect routing or physical damage may restrict the intended return flow.
• Damaged mounting brackets: Loose supports may allow vibration and abrasion against surrounding components.
• Burning oil-like smell: Leaking hydraulic fluid contacting hot engine or exhaust surfaces may produce an unpleasant odour.
• Unusual hydraulic system noises: Fluid restriction, aeration or low fluid levels may cause abnormal steering system sounds.

Why Replacement Matters:
Replacing a defective power steering return line is important for maintaining reliable steering assistance and preventing unnecessary hydraulic fluid loss.

A damaged return line may allow fluid to escape from the system, gradually reducing the quantity available for circulation.

If the fluid level becomes too low, the power steering pump may draw in air rather than a consistent supply of hydraulic fluid. This can lead to abnormal pump noise, reduced steering assistance and increased mechanical wear.

A restricted return line may also interfere with normal fluid circulation.

Installing a Genuine Porsche replacement Rear Power Steering Return Line helps to:

• Restore fluid circulation: Maintain the intended hydraulic return path.
• Prevent power steering leaks: Replace damaged pipework and leaking connections.
• Maintain reliable steering assistance: Support the fluid circulation required for consistent hydraulic steering operation.
• Protect the power steering pump: Reduce the risk of pump damage associated with significant fluid loss.
• Reduce abnormal pump noise: Help resolve whining caused by fluid loss from a confirmed leaking return line.
• Maintain hydraulic system integrity: Restore a secure, properly sealed return connection.
• Prevent further fluid contamination: Replace compromised connections that may expose the circuit to contamination.
• Reduce the risk of unexpected steering problems: Address developing leaks before the system loses significant fluid.
• Preserve correct factory routing: Maintain the intended rear engine compartment pipe configuration.
• Support power steering servicing: Provide replacement pipework during pump or associated hydraulic component repairs.
• Prevent damage to surrounding components: Reduce unwanted hydraulic fluid leakage around the engine compartment.
• Maintain vehicle originality: Preserve the factory hydraulic steering arrangement.
• Support long-term reliability: Replace ageing or damaged hydraulic components before deterioration worsens.
• Maintain Genuine Porsche quality: Use an original equipment component intended for the applicable Porsche 996 steering system.

Replacement is particularly recommended when inspection confirms cracking, corrosion, damaged fittings, physical deformation or persistent fluid leakage from the line.

When replacing the rear return line, the adjoining pressure pipe, centre return line, pump connections and associated seals should also be inspected.

Related reference numbers
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99634744103

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Power steering return line, for RHD cars

Fits:
Porsche 986 Boxster >>2001 RHD
Porsche 996 Carrera >>2001 RHD, Rear-wheel drive
F             >> 99-4S630 356
F             >> 99-4S603 928
F             >> 99-4S642 725
Porsche 996 Turbo GT2 2001 RHD
Porsche 996 GT3 >>2001 RHD

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Diagram ref no 2

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99634745012

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Replacement Pipes (Steel) For LHD Steering Rack (Pair)
For Left Hand Drive Cars ONLY! 

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 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

Other than buying a completely new steering rack or having your existing steering rack refurbished, which are both very expensive options, we now offer replacement steering rack pipes which are normally not available separately, the two replacement pipes fit to the steering rack, these pipes normally deteriorate. The steering rack of a power-assisted car needs a hydraulic circuit: a pressure line (high pressure) from the power steering pump (or pump + reservoir assembly) to the steering rack, and a return line (low pressure) from the rack back to the reservoir (or pump return side). 

Related reference numbers
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99634701111P

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Replacement Pipes (Steel) For RHD Steering Rack (Pair)
For Right Hand Drive Cars ONLY!  

Other than buying a completely new steering rack or having your existing steering rack refurbished, which are both very expensive options, we now offer replacement steering rack pipes which are normally not available separately, the two replacement pipes fit to the steering rack, these pipes normally deteriorate. The steering rack of a power-assisted car needs a hydraulic circuit: a pressure line (high pressure) from the power steering pump (or pump + reservoir assembly) to the steering rack, and a return line (low pressure) from the rack back to the reservoir (or pump return side). 

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 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  

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99634701210P

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Steering rack pressure line, Supply. For RHD cars.

Fits:
For RHD cars
Porsche 996 2002>> All-wheel drive (M339)

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Diagram ref no 1

Related reference numbers
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99634745229

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Steering rack return line for RHD cars.

Fits
RHD cars / All-wheel drive (M339)
Porsche 996 C4 / C4S 2002>>
Porsche 996 Turbo 2002>>

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Diagram ref no 2

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99634745027

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Support bracket for solid brake, clutch and power steering lines. 

Fits:
Porsche 986 Boxster - 1997 to 2004
Porsche 987.1 Boxster - 2005 to 2008
Porsche 987.1 Cayman - 2005 to 2008
Porsche 996 - 1997 to 2005
Porsche 997.1 - 2005 to 2008

Diagram ref no 17

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99635554300

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Threaded joint for power steering pipes, NW10

Fits:
Porsche 996 Carrera 2000-05
F             >> 99-4S630 356
F             >> 99-4S603 928
F             >> 99-4S642 725

Porsche 996 Turbo 2001-05
F             >> 99-4S680 654
F             >> 99-4S670 658
F             >> 99-4S695 107

Porsche 996 GT3 1999-05
F             >> 99-4S691 629

Porsche 997.1 Carrera 2005-08
Porsche 986 Boxster 1997-04
Porsche 987.1 Boxster 2005-08
Porsche 987C.1 Cayman 2006-08

Click 'Zoom in' for large parts diagram.
Diagram ref no 16

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99923055110

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Threaded joint for power steering pipes, NW6

Fits:
Porsche 996 Carrera 2000-05
F             >> 99-4S630 356
F             >> 99-4S603 928
F             >> 99-4S642 725

Porsche 996 Turbo 2001-05
F             >> 99-4S680 654
F             >> 99-4S670 658
F             >> 99-4S695 107

Porsche 996 GT3 1999-05
F             >> 99-4S691 629

Porsche 997.1 Carrera 2005-08
Porsche 986 Boxster 1997-04
Porsche 987.1 Boxster 2005-08
Porsche 987C.1 Cayman 2006-08

Click 'Zoom in' for large parts diagram.
Diagram ref no 15

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