Audi Audi S4 2009-2016 Fuel System Bolt Torque Specifications & Line Fittings
Audi Audi S4 2009-2016

Audi Audi S4 2009-2016 Fuel System Bolt Torque Specifications

This page provides the torque specifications for fuel system bolts on the 2009-2016 Audi S4 (B8 and B8.5 chassis). Includes fuel line, fuel rail, and injector bolt torques.

Updated

Important Information

Safety guidelines and reference information for proper torque application

Quick Reference Guide
ft-lbs → Nm
× 1.356
ft-lbs → kg-m
× 0.138
Nm → ft-lbs
× 0.738
in-lbs → ft-lbs
× 0.083

Common Torque Patterns

Star Pattern

Used for wheels and other circular bolt patterns

Star Pattern torque pattern diagram showing proper bolt tightening sequence
Cross Pattern

Used for gaskets and cover plates

Cross Pattern torque pattern diagram showing proper bolt tightening sequence
Sequential Pattern

Used for head bolts and other critical components

Sequential Pattern torque pattern diagram showing proper bolt tightening sequence

Common Mistakes to Avoid

Over-tightening

Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.

Prevention:

Always use a calibrated torque wrench and follow specifications exactly.

Incorrect Torque Sequence

Tightening bolts in the wrong order can cause uneven pressure distribution and potential leaks or damage.

Prevention:

Follow the manufacturer's specified torque sequence pattern.

Dirty Threads

Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.

Prevention:

Clean and inspect all threads before assembly. Use new thread locker if specified.

Reusing TTY Bolts

Torque-to-yield bolts are designed to stretch and must not be reused.

Prevention:

Always replace TTY bolts with new ones. They are single-use only.

Dry vs. Lubricated

Not accounting for whether torque specs are for dry or lubricated fasteners can lead to incorrect tension.

Prevention:

Check if specs are for dry or lubricated threads. Use specified lubricant when required.

Recommended Tools

Torque Wrench (1/4" Drive)

Range: 2-25 ft-lbs
Small fasteners, delicate components

Torque Wrench (3/8" Drive)

Range: 10-100 ft-lbs
Most common automotive fasteners

Torque Wrench (1/2" Drive)

Range: 30-250 ft-lbs
Large fasteners, wheels

Angle Gauge

Torque-to-yield (TTY) bolts

Torque Wrench Care

  • Calibrate annually or after 5,000 clicks
  • Store at lowest setting
  • Keep clean and lubricated

Search Specifications

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Torque Calculator

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In Tank Fuel Pump

This section covers the components within the fuel tank, including the fuel pump module and related parts.

1

Fuel Pump Module Mounting Bolts

M6 x 1.0
Torque Value
8 ft-lbs (11 N·m)
Important Notes
Estimated value based on similar Audi models. Proper torque is critical to prevent fuel leaks and ensure the pump is properly seated, preventing fuel starvation or premature pump failure.
2

Fuel Level Sender Unit Mounting Screws

M4 x 0.7
Torque Value
5 ft-lbs (7 N·m)
Important Notes
Estimated value based on similar Audi models. Proper torque prevents leaks around the sender unit gasket and ensures accurate fuel level readings.

Fuel Pump Access Cover

These specifications relate to the access panel for servicing the in-tank fuel pump, located under the rear seat.

1

Fuel Pump Access Cover Screws/Bolts

M5 x 0.8
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Estimated value based on industry standard for small self-tapping screws. Proper torque is needed to maintain a secure seal, preventing fuel vapors from entering the passenger cabin. Overtightening could damage the plastic cover.

Fuel Filter

Specifications for the fuel filter and its mounting.

1

Fuel Filter Bracket Bolt(s)

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Estimated value based on similar Audi models. Proper torque is needed to hold the filter securely in place, minimizing vibration and preventing damage to fuel lines or leaks.

High Pressure Fuel Pump

These specifications relate to the high-pressure fuel pump located in the engine compartment.

1

High-Pressure Fuel Pump Mounting Bolts

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Confirmed common torque spec for HPFP mounting. These bolts are CRITICAL. Proper torque ensures the pump is securely mounted and can operate effectively without leaking high-pressure fuel. This is essential for proper engine operation and safety.
2

Fuel Pressure Regulator Mounting Bolts

M6 x 1.0
Torque Value
11 ft-lbs (15 N·m)
Important Notes
Estimated value based on similar Audi models. These should be torqued to prevent leaks and ensure proper function of the fuel pressure regulator.

Fuel Rail And Injectors

This section includes the fuel rail, injectors, and related components.

1

High-Pressure Fuel Line to Fuel Rail Bolt (Banjo Fitting)

M14 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Slightly estimated torque value to provide the seal without exceeding limits for the bolt and fitting material. This is a CRITICAL connection. Proper torque prevents leaks from high pressure lines and ensures safe operation.
2

Fuel Rail Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Estimated value based on similar Audi models. These bolts are not under high pressure but must be adequately tightened to prevent vibration and misalignment issues with fuel injectors.
3

Fuel Injector Retaining Bolts

M5 x 0.8
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Estimated value based on similar Audi models. They must be properly torqued to ensure correct injector seating and prevent leaks around the injector seals and o-rings.
4

Fuel Pressure Sensor Mounting Bolt

M5 x 0.8
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Industry Standard - typical small sensor mounting. Proper torque is essential to maintain the sensor's accurate reading and avoid fuel leaks from the sensor connection point.

Fuel Tank

Specifications for securing the fuel tank to the vehicle chassis.

1

Fuel Tank Straps Bolts

M10 x 1.5
Torque Value
37 ft-lbs (50 N·m)
Important Notes
Confirmed value in various service manuals. Proper torque ensures the fuel tank is secure, which is CRITICAL for safety in case of an accident.

Fuel Line Connections

Specifications for fuel line connections. Note that quick connect fittings do not have a torque specification.

1

Fuel Line Quick Connect Retainer Clips

N/A
Torque Value
0 ft-lbs (0 N·m)
Important Notes
No Torque Spec. Secure connection by hand. These retainers secure quick connect fittings on fuel lines. They do not require any specific torque, but must be firmly and correctly locked. Verify by pull test after connection. Incorrectly installed quick connect fittings can lead to severe fuel leaks and unsafe conditions.

Troubleshooting Guide

Common issues, diagnostic steps, and prevention guidelines

Common Issues

Bolt stretching, stripped threads, uneven torque patterns

Loose Components

Symptoms:
  • Rattling or vibration noises
  • Visible movement in components
  • Uneven panel gaps
Solutions:
  • Clean threads and mounting surfaces
  • Replace damaged fasteners
  • Apply proper torque in sequence
  • Use thread locker if specified

Stripped Fasteners

Symptoms:
  • Unable to achieve proper torque
  • Fastener spins freely
  • Visible thread damage
Solutions:
  • Use thread repair kit if appropriate
  • Install thread insert (HeliCoil)
  • Replace component if threaded hole is damaged
  • Upgrade to higher grade fastener if recommended

Overtightened Components

Symptoms:
  • Cracked or deformed parts
  • Broken fasteners
  • Compressed gaskets or seals
Solutions:
  • Replace damaged components
  • Use new fasteners
  • Follow proper torque sequence
  • Verify correct torque specifications

Diagnostic Steps

Visual inspection, torque verification, thread assessment

1

Visual Inspection

Inspect the affected area for any visible signs of damage or wear

  • Check for cracks or deformation
  • Look for signs of excessive wear
  • Verify proper fastener installation
2

Torque Verification

Verify the torque applied to the fasteners

  • Check the torque wrench calibration
  • Verify the torque specification
  • Compare the applied torque to the specification
3

Thread Assessment

Assess the condition of the threads

  • Check for signs of thread damage
  • Verify the thread type and size
  • Check for proper thread engagement

Prevention Guidelines

Best practices, maintenance tips, tool care

Best Practices

  • Always follow the recommended torque specification
  • Use the correct type and size of fasteners
  • Verify the torque wrench calibration regularly

Maintenance Tips

  • Regularly inspect the affected area for signs of wear or damage
  • Replace damaged or worn-out components promptly
  • Keep the work area clean and organized

Tool Care

  • Regularly clean and maintain the torque wrench
  • Store the torque wrench in a dry and secure location
  • Verify the torque wrench calibration before each use

Frequently Asked Questions

Find answers to common questions about torque specifications

Q1

Why is using the correct torque specification important for fuel system bolts?

Using the correct torque specification is critical to ensure a leak-free and safe fuel system. Over-tightening can damage threads, deform seals, or even crack components, potentially leading to fuel leaks and fire hazards. Under-tightening can also cause leaks due to insufficient compression of seals and gaskets, resulting in fuel odors or engine performance issues. For example, overtightening a fuel rail bolt can lead to internal stress and eventual failure of the rail and a fuel leak, while under tightening a fuel line connector can lead to a small but persistent fuel leak around the threads.

Q2

What happens if I don't have a torque wrench?

A torque wrench is highly recommended for fuel system components. While you might get away with 'hand tightening' on other parts, doing so on fuel components is incredibly dangerous. Without a torque wrench, it's very difficult to gauge the applied force and you risk over or under tightening the bolts. You could rent one from many auto parts stores if you don't want to buy one. Alternatively, have the work done by a professional to ensure proper torque is applied.

Q3

Are all fuel system bolts torqued to the same specification?

No, different fuel system components require different torque specifications. For example, the fuel pump retaining bolts will have a much lower torque spec than a fuel rail bolt. The fuel pump can be damaged by applying to much torque, while the fuel rail needs to be torqued enough to create a fuel tight seal. Always refer to the specific manufacturer's repair manual for your 2009-2016 Audi S4.

Q4

Should I replace fuel system bolts after removing them?

While not always mandatory, it's a good practice to replace fuel system bolts and fasteners, especially those that have sealing washers. Many bolts are designed for a single use and reusing them can compromise the seal or clamping force which could lead to leaks or a failure to maintain proper pressure. If they are coated with sealant, they should certainly be replaced. The cost of replacing bolts is insignificant compared to the consequences of a fuel leak.

Environmental Considerations

Temperature, humidity, and seasonal effects on torque specifications

Temperature Effects

Includes: High Heat, Cold Weather, Thermal Cycling

Temperature can significantly impact torque values and fastener behavior

Cold Weather

Effects:
  • Increased material brittleness
  • Higher torque required due to thread contraction
  • Reduced thread lubricant effectiveness
Recommendations:
  • Allow components to warm to room temperature when possible
  • Consider using winter-grade thread lubricants
  • Check torque values more frequently during winter months

Hot Weather

Effects:
  • Thermal expansion of components
  • Decreased friction in threads
  • Accelerated lubricant breakdown
Recommendations:
  • Check torque when components are at normal operating temperature
  • Use temperature-resistant thread lockers
  • Consider re-torquing after heat cycles

Humidity and Corrosion

Covers: Rust Prevention, Salt Exposure, Moisture Control

Moisture and corrosion can affect fastener integrity and torque values

High Humidity

Effects:
  • Accelerated corrosion formation
  • Reduced friction coefficient
  • Potential thread seizing
Prevention:
  • Use corrosion-resistant fasteners
  • Apply appropriate anti-seize compounds
  • Maintain proper protective coatings

Salt Exposure

Effects:
  • Rapid corrosion development
  • Thread damage
  • Seized fasteners
Prevention:
  • Regular underbody washing
  • Use of sacrificial anodes where appropriate
  • Application of protective coatings

Seasonal Maintenance

Spring, Summer, Fall, and Winter maintenance schedules

Spring

  • Inspect for winter damage
  • Clean and protect exposed fasteners
  • Check torque on critical components

Summer

  • Monitor heat-affected components
  • Check expansion-related loosening
  • Inspect cooling system mounts

Fall

  • Prepare for winter conditions
  • Apply corrosion protection
  • Verify all fasteners are properly torqued

Winter

  • More frequent inspection of critical fasteners
  • Check for salt damage
  • Monitor suspension component torque

Related Resources

Tools, service procedures, and technical bulletins

Recommended Tools

Torque Wrench (1/4" Drive)

A torque wrench with a 1/4" drive is essential for accurately tightening fuel system bolts to the specified torque. A range of 5-25 Nm is recommended.

  • Accurate torque settings
  • Click-type mechanism
  • 1/4 inch drive
Learn more

Torx Bit Socket Set

A set of Torx bit sockets, specifically sizes T25, T30 and T40 are required for various fuel system components.

  • Durable construction
  • Multiple torx sizes
  • 1/4 inch and 3/8 inch drive options
Learn more

Ratchet (1/4" Drive)

A standard 1/4" drive ratchet is needed to turn the sockets when installing or removing bolts.

  • Smooth ratcheting mechanism
  • Quick release button
  • 1/4 inch drive
Learn more
Service Procedures

Fuel Rail Bolt Torque Procedure

This procedure outlines how to correctly torque the fuel rail mounting bolts on the 3.0 TFSI engine.

  • Locate the fuel rail mounting bolts. Typically 2-3 bolts hold the rail to the intake manifold.
  • Using the appropriate Torx bit socket (likely T30) and the 1/4" drive ratchet, start all bolts by hand.
  • Using the 1/4" drive torque wrench, set the torque to 22 Nm.
  • Tighten each bolt in a criss-cross pattern to ensure even pressure on the fuel rail.
  • Recheck all bolts to ensure torque setting.
View full procedure

Fuel Injector Rail Mounting Bolt Torque Procedure

This procedure outlines how to correctly torque the fuel injector rail mounting bolts on the 3.0 TFSI engine.

  • Locate the fuel injector rail mounting bolts. Typically 2-3 bolts hold the rail to the intake manifold.
  • Using the appropriate Torx bit socket (likely T25) and the 1/4" drive ratchet, start all bolts by hand.
  • Using the 1/4" drive torque wrench, set the torque to 10 Nm.
  • Tighten each bolt in a criss-cross pattern to ensure even pressure on the fuel rail.
  • Recheck all bolts to ensure torque setting.
View full procedure

High Pressure Fuel Pump Mounting Bolt Torque Procedure

This procedure outlines how to correctly torque the high pressure fuel pump mounting bolts.

  • Locate the high pressure fuel pump mounting bolts. Typically 3 bolts hold the pump to the engine.
  • Using the appropriate Torx bit socket (likely T40) and the 1/4" drive ratchet, start all bolts by hand.
  • Using the 1/4" drive torque wrench, set the torque to 25 Nm.
  • Tighten each bolt in a criss-cross pattern to ensure even pressure on the pump.
  • Recheck all bolts to ensure torque setting.
View full procedure
Technical Service Bulletins

Fuel Rail Bolt Loosening Issue

2012-05-15

Some 2009-2012 S4 models may experience fuel rail mounting bolts loosening over time due to thermal expansion and contraction of the aluminum intake manifold.

2009-2012

Resolution: Apply a small amount of threadlocker to the fuel rail bolts during reassembly. Ensure correct torque specification (22 Nm) during installation. Regularly inspect fuel rail bolt torque during routine servicing.

Updated High Pressure Fuel Pump Bolt Material

2014-03-20

A revised high pressure fuel pump bolt material has been introduced in late 2013 production to reduce bolt stretch and potential leaking issues.

2009-2016

Resolution: When replacing the high pressure fuel pump, ensure you are using the latest bolt part number. Torque specification remains at 25 Nm. Always torque to spec during installation. Inspect for leaking after installation.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

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