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Reservoir / Tank

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91135535100
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Brake Fluid Reservoir Cap with Contact.

porsche

Fits:
Porsche 911 1987-89

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Diagram ref no 2.

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91135535100
91135535100

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90135590800/1
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Brake Fluid Reservoir Cap Seal 

High-quality replacement brake fluid reservoir cap seal designed for classic Porsche 911 (1968–1986), Porsche 914, and Porsche 928 models.

This gasket fits inside the brake fluid reservoir cap, providing a secure seal to prevent fluid leakage and protect the braking system from moisture and contamination.

Fits:

  • Porsche 911 1965-1968 2.0L / 912 SWB (F)
  • Porsche 911 1968-1973 2.2L / 2.4L / 2.7L RS LWB (F)
  • Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
  • Porsche 911 1978-1983 3.0L / SC
  • Porsche 911 1984-1986 3.2L
  • Porsche 911 1987-1989 3.2L G50
  • Porsche 911 1975-1977 3.0L Turbo (930)
  • Porsche 911 1978-1989 3.3L Turbo (930)
  • Porsche 928 4.5L 1978-82
  • Porsche 928S 4.7L 1981-83
  • Porsche 928S2 4.7L 1984-86
  • Porsche 928S4 5.0L 1987-92
  • Porsche 928GT 5.0L 1989-91
  • Porsche 928GTS 5.4L 1992-95
  • Porsche 914 (1970-1976)
  • Porsche 912E 4CYL 1976

Diagram ref no 3

Manufactured to OEM specifications, this seal ensures reliable performance and is an essential component for maintaining proper brake system function, especially on classic and air-cooled Porsche models.

Key Features

• Direct replacement brake fluid reservoir cap seal
• Fits inside reservoir cap for secure sealing
• OEM-style fit and performance
• Helps prevent brake fluid leaks and contamination
• Durable material for long-term reliability
• Ideal for maintenance and restoration

Function and Purpose

This cap seal ensures a tight closure of the brake fluid reservoir.

It helps to:

• Prevent brake fluid leakage
• Protect system from moisture ingress
• Maintain correct hydraulic pressure
• Preserve braking system performance

Why Replace Your Brake Fluid Cap Seal

Over time, seals can degrade due to exposure to brake fluid and environmental conditions.

Common issues include:

• Cracked or hardened rubber
• Fluid seepage around the cap
• Moisture entering the system
• Reduced braking performance

Replacing the seal helps maintain safe and reliable braking.



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

90135590800
90135590800

The product you are viewing cross references to these numbers
Special Order item
90135590800
Product Information
Product Information
Brake Fluid Reservoir Lid Seal.

Fits:
Porsche 911 1968-86
Porsche 911 (930) Turbo 1975-77
Porsche 914 1970-76
Porsche 928 1978-95

Diagram ref no 3

Related reference numbers
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90135590800
90135590800

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About Reservoir / Tank

High-Quality Hydraulic Reservoirs & Tanks for Stable, Reliable Brake & Clutch Performance

Hydraulic reservoirs—also known as fluid tanks or expansion containers—store and supply hydraulic fluid for brake and clutch systems. These reservoirs ensure a stable fluid level, maintain pressure balance and prevent air from entering the hydraulic circuits. Whether used in performance vehicles, classic models or daily drivers, the reservoir plays a crucial role in keeping hydraulic systems responsive, consistent and safe.

A healthy reservoir ensures the brake and clutch systems always receive the correct amount of fluid, preventing pressure loss, contamination and system failure.

What Hydraulic Reservoirs & Tanks Do

Reservoirs and hydraulic tanks support the system by:

  • Storing brake or clutch fluid for use by the master cylinder
  • Maintaining correct fluid levels during temperature and pressure changes
  • Allowing fluid expansion to avoid over-pressurisation
  • Preventing air entry into the hydraulic system
  • Reducing contamination via filtered caps or sealed designs
  • Supporting consistent pedal feel during demanding conditions

A reliable reservoir helps ensure stable braking and clutch engagement across all temperatures and driving environments.

Why Hydraulic Reservoirs Commonly Fail

Despite being simple components, reservoirs are exposed to heat, vibration and corrosive fluids. Over time, they may deteriorate or fail due to:

  • Cracking or brittleness from age and UV exposure
  • Internal contamination from degraded seals or old fluid
  • Leaks caused by stress fractures or weakened hose connections
  • Discolouration or clouding, making fluid levels hard to read
  • Warped or loose caps leading to air entry
  • Corrosion on metal mounting points or fittings
  • Heat-related deformation reducing sealing effectiveness

Typical symptoms include fluid loss, soft pedal feel, brake warning lights, or inconsistent clutch operation.

Why You Should Replace a Worn or Damaged Hydraulic Reservoir

Replacing an old or failing reservoir with a high-quality, precision-built alternative designed to match original hydraulic performance ensures your vehicle’s braking and clutch systems remain safe and dependable.

Benefits include:

  • Restored fluid capacity and pressure stability
  • Clear fluid visibility for accurate level checks
  • Prevention of leaks and air ingress
  • More consistent pedal feel in brake and clutch systems
  • Reduced risk of contamination and hydraulic failure
  • Improved long-term safety and reliability

A new reservoir is a simple, cost-effective upgrade that protects the entire hydraulic system.

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