Audi Audi S6 2012-2018 Fuel System Bolt Torque Specifications & Line Fittings
Audi Audi S6 2012-2018

Audi Audi S6 2012-2018 Fuel System Bolt Torque Specifications

This page provides detailed torque specifications for fuel system bolts on the 2012-2018 Audi S6 (C7) generation. Includes information on fuel line, fuel rail, and fuel pump 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

Search by component name, bolt size, or description

Torque Calculator

Convert between different torque units

Fuel Pump Assembly

This subsystem includes the components located inside the fuel tank, specifically the fuel pump module and the fuel level sender unit.

1

Fuel Pump Module Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Secures the fuel pump module to the fuel tank. Proper torque prevents leaks and ensures the pump stays properly positioned in the tank.
2

Fuel Level Sender Unit Mounting Bolts

M5 x 0.8
Torque Value
3.5 ft-lbs (4.7 N·m)
Important Notes
Secures the fuel level sending unit to the fuel tank. Proper torque prevents damage to the sending unit and fuel leaks.

Fuel Rail And Components

This subsystem comprises the fuel rail, fuel injectors, fuel pressure sensor, and the high-pressure fuel pump, all mounted within the engine bay.

1

Fuel Rail Mounting Bolts

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Fastens the fuel rail to the intake manifold. Correct torque ensures a secure and leak-free connection. Critical for maintaining fuel pressure and preventing leaks.
2

Fuel Injector Retaining Bolts

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Hold the fuel injectors in place on the fuel rail. Prevents movement and ensures proper injector sealing. Too much torque can damage the injectors or the fuel rail.
3

Fuel Pressure Sensor Bolt

M5 x 0.8
Torque Value
3.5 ft-lbs (4.7 N·m)
Important Notes
Secures the fuel pressure sensor to the fuel rail. Correct torque is crucial to prevent leaks and ensures sensor accuracy.
4

High-Pressure Fuel Pump Mounting Bolts

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Fastens the high-pressure fuel pump to the engine block. Correct torque is crucial for pump functionality and prevents vibration and leaks.

Fuel Line Connections

This subsystem details the torque specifications for various fuel line connections, including banjo bolts and fittings, which are vital for a leak-free fuel system.

1

High-Pressure Fuel Line Banjo Bolt

M14 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Connects the high-pressure fuel line to the high-pressure fuel pump or fuel rail. Proper torque with new crush washers ensures a leak-free and pressure-tight seal. This is a critical safety fastener.
2

Low-Pressure Fuel Line Banjo Bolt

M12 x 1.5
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Connects the low-pressure fuel lines to various components. Proper torque, usually with new crush washers, is required for a leak-free connection.
3

Fuel Line Fitting/Connector Bolts (M6)

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Often used on auxiliary lines or connections. Ensures a secure connection without overtightening which can damage fittings. Estimated value.
4

Fuel Line Fitting/Connector Bolts (M8)

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Often used on auxiliary lines or connections. Ensures a secure connection without overtightening which can damage fittings. Estimated value.

Evaporative Emission Control System

This subsystem includes the components of the EVAP system, namely the EVAP canister and the purge valve, which are responsible for managing fuel vapor emissions.

1

EVAP Canister Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Fastens the EVAP canister to the vehicle's chassis. Proper torque prevents rattling and ensures the canister is secure.
2

EVAP Purge Valve Mounting Bolt

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Secures the EVAP purge valve to the intake manifold. Proper torque prevents leaks and ensures the valve functions correctly.

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

What happens if I overtighten fuel system bolts?

Overtightening fuel system bolts can lead to several issues. Specifically, you risk damaging the threads in the fuel rail, pump, or other components, potentially leading to leaks. Furthermore, you could crush sealing washers or O-rings, causing fuel leaks and creating a fire hazard. For example, overtightening a banjo bolt on the high-pressure fuel pump can crack the pump housing. Always use a calibrated torque wrench.

Q2

What happens if I under-tighten fuel system bolts?

Under-tightening fuel system bolts is equally dangerous. Insufficient torque can lead to fuel leaks, which are a significant fire hazard. Additionally, loose connections can cause erratic fuel pressure, leading to engine misfires or a no-start condition. For example, an under-tightened fuel line connection to an injector could result in a spray of fuel under high pressure, creating a dangerous situation.

Q3

Should I use new bolts or washers when working on the fuel system?

It's highly recommended to use new fuel system bolts and washers whenever they are removed, especially for sealing connections. These components are often designed for a single use and may become deformed after being torqued once. Reusing them can lead to improper sealing and leaks. For example, banjo bolts and crush washers should always be replaced.

Q4

Do torque specifications vary depending on the component?

Yes, absolutely. Torque specifications are specific to each bolt size and the material of the components being joined. The torque value for a fuel rail mounting bolt will differ significantly from the torque for an injector hold-down bolt or a fuel pump inlet connection. Consult the official Audi service manual or a reputable online database for the correct torque specifications. Using general specifications is a bad idea. For example, the fuel pump inlet has a lower torque spec than the fuel rail mounting bolts.

Q5

How often should I inspect my fuel system components and bolt torques?

While not part of routine maintenance, whenever you're working in the engine bay, particularly near the fuel system, it's a good idea to visually inspect for any signs of leaks or loosened bolts. If you suspect a leak, never use an open flame to investigate. During extensive work on the fuel system or anytime you disturb a connection, double check the torque on the bolts for peace of mind.

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

A calibrated torque wrench is essential for tightening fuel system bolts to the precise specifications.

  • Precise torque measurement
  • Adjustable range to cover fuel system specs
Learn more

Socket Set (Metric)

A set of metric sockets, including common sizes for fuel line connections and fuel rail fasteners, is needed.

  • Various sizes for different fasteners
  • Durable construction for repetitive use
Learn more

Crowfoot Wrench Set (Metric)

Crowfoot wrenches are useful for accessing fuel line fittings that may be difficult to reach with a standard socket.

  • Allows torque application in tight spaces
  • Open-end design for line connections
Learn more
Service Procedures

Fuel Rail Bolt Torque Procedure

This procedure outlines the steps for correctly torquing the fuel rail mounting bolts on a 2012-2018 Audi S6.

  • Locate the fuel rail mounting bolts.
  • Using the correct socket, loosely thread each bolt into position.
  • Refer to specifications for the correct torque setting for your model year.
  • Using a calibrated torque wrench, tighten each bolt to the specified torque in a criss-cross pattern.
  • Double-check all bolts to ensure they have been torqued correctly.
View full procedure

High Pressure Fuel Line Fitting Torque Procedure

This procedure outlines the steps for correctly torquing the high pressure fuel line fittings.

  • Locate the high pressure fuel line connection.
  • Using the correct size crowfoot wrench (if necessary) or open end wrench, loosely thread each fitting into position.
  • Refer to specifications for the correct torque setting for your model year.
  • Using a calibrated torque wrench, tighten the fitting to the specified torque.
  • Double-check the fitting to ensure it has been torqued correctly.
View full procedure

Fuel Injector Bolt Torque Procedure

This procedure outlines the steps for correctly torquing the fuel injector mounting bolts.

  • Locate the fuel injector mounting bolts.
  • Using the correct socket, loosely thread each bolt into position.
  • Refer to specifications for the correct torque setting for your model year.
  • Using a calibrated torque wrench, tighten each bolt to the specified torque.
  • Double-check all bolts to ensure they have been torqued correctly.
View full procedure
Technical Service Bulletins

Fuel Line Connection Leakage

2015-03-15

Reports of fuel leaks originating from improperly torqued fuel line connections have been observed. It was found some vehicles were under-torqued from the factory.

2012-2015

Resolution: Inspect all fuel line connections and verify they are torqued to the correct specification. Re-torque any under-torqued connections.

Fuel Rail Bolt Degradation

2017-08-22

There have been reports of fuel rail bolts showing signs of corrosion and material fatigue. This can affect the clamping force and torque value.

2012-2018

Resolution: Replace fuel rail bolts with updated OE versions. Ensure proper torque specification are applied using a calibrated torque wrench.

High Pressure Fuel Pump Mounting Bolt Issues

2016-01-10

Some cases of High Pressure Fuel Pump bolts loosening over time have been recorded. This may result in poor fuel delivery, fuel leaks, and noises. This issue is usually caused by insufficient torque at the factory.

2012-2017

Resolution: Inspect the high pressure fuel pump mounting bolts and re-torque to the manufacturers specification. If bolts are damaged or show signs of fatigue, replace with OE components.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

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