Audi Audi S8 2019-present Exhaust System Bolt Torque Specifications & Gasket Sealing
Audi Audi S8 2019-present

Audi Audi S8 2019-present Exhaust System Bolt Torque Specifications

Detailed torque specifications for exhaust bolts on the 2019-present Audi S8, including downpipe, mid-pipe, and muffler connections.

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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Turbocharger Connections

This section covers the torque specifications for bolts connecting the exhaust downpipes to the turbocharger housings. These connections are critical for preventing exhaust leaks and maintaining proper turbocharger performance.

1

Downpipe to Turbocharger Flange Bolts

M10 x 1.5
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Critical connection; use a crisscross (star) pattern during tightening to ensure even pressure. New bolts are recommended.

Downpipe Midpipe Connections

This section includes torque specifications for bolts connecting the downpipes to the mid-pipe section of the exhaust system. Proper sealing is essential to maintain efficient exhaust flow.

1

Downpipe to Mid-Pipe Flange Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Use a crisscross (star) pattern for even tightening. Ensure the flanges are flush before tightening.

Midpipe Connections

This section contains torque specifications for bolts used to connect sections of the mid-pipe together. These connections require secure sealing to ensure proper exhaust flow.

1

Mid-Pipe Connecting Bolts

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Ensure proper alignment of pipe sections before tightening bolts. Estimated value.

Exhaust Clamps

This section provides the torque specifications for exhaust clamp bolts, used to secure various sections of the exhaust piping. Proper torque is important to ensure a leak-free connection and allow for slight thermal expansion.

1

Exhaust Clamp Bolts

M8 x 1.25
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Do not over-tighten. Ensure the clamp is evenly placed around the pipe. Estimated value.

Muffler Mounting

This section details the torque specifications for bolts used to mount the mufflers/silencers to the chassis. This is critical to prevent shaking, noise, and potential damage.

1

Muffler/Silencer Mounting Bolts (M8)

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Check for proper alignment before final tightening. Ensure the muffler hangers are properly seated. Estimated value.
2

Muffler/Silencer Mounting Bolts (M10)

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Check for proper alignment before final tightening. Ensure the muffler hangers are properly seated. Estimated value.

Hanger Brackets

This section covers the torque specifications for bolts securing the exhaust hanger brackets to the vehicle's chassis, ensuring the exhaust system is properly supported.

1

Exhaust Hanger Bracket Bolts to Chassis

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Ensure the brackets are properly aligned before tightening. Estimated value.

Rear Muffler Connections

This section covers the torque specifications for bolts connecting the rear muffler section to the mid-pipe. These connections are important for exhaust system integrity and sealing.

1

Exhaust Flange Bolts to Rear Muffler

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Use a crisscross (star) pattern for even tightening. Ensure the flanges are flush before tightening.

Oxygen Sensors

This section details the torque specification for installing oxygen (O2) sensors into the exhaust system.

1

O2 Sensor to Exhaust Pipe

Specialized O2 Sensor Thread
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Use an O2 sensor socket or crows foot. Do not overtighten. Estimated value.

Heat Shields

This section outlines the torque specs for heat shield bolts, protecting components from excessive heat.

1

Exhaust System Heat Shield Bolts

M6 x 1.0
Torque Value
8 ft-lbs (11 N·m)
Important Notes
Tighten until snug, do not over tighten. Estimated value.

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 are torque specifications so important for exhaust bolts?

Using the correct torque specifications ensures a proper seal and prevents leaks. Over-tightening can damage bolts and exhaust components, leading to costly repairs, while under-tightening can result in leaks and premature failure.

Q2

What happens if I overtighten exhaust bolts?

Overtightening can stretch or break bolts, damage the exhaust flanges, and crush gaskets. This often leads to leaks, rattling, and even the need to replace entire sections of the exhaust system. For instance, overtightening the downpipe bolts could damage the mating surfaces on the turbo and exhaust.

Q3

What happens if I undertighten exhaust bolts?

Undertightening bolts will not create a proper seal between exhaust components. This will result in exhaust leaks, which can be noisy, dangerous (allowing exhaust fumes into the cabin), and can cause your vehicle to fail emissions tests. An example is an undertightened clamp connection which could cause an exhaust leak after a bump or under normal vibration.

Q4

Should I use new gaskets when reassembling the exhaust?

Yes, it is strongly recommended to use new gaskets every time you disassemble the exhaust system. Old gaskets can be compressed, warped, or cracked, and may not properly seal when reused, leading to leaks. For instance, reusing a gasket between the cat-back section will likely not provide a lasting leak-free seal.

Q5

Do I need any special tools to torque exhaust bolts correctly?

Yes, a torque wrench is essential for properly tightening exhaust bolts to the manufacturer's specifications. Using a regular wrench and tightening by feel is not accurate and will lead to either over-tightening or under-tightening. You should also use the correct size sockets and extensions to reach all bolts properly.

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 (1/2-inch Drive)

A calibrated torque wrench is essential for applying accurate torque to exhaust bolts. A 1/2-inch drive is typically needed for the larger bolts found in exhaust systems.

  • Wide torque range (e.g., 20-150 ft-lbs)
  • Click-type mechanism for accurate readings
  • Durable construction
Learn more

Torque Wrench (3/8-inch Drive)

A smaller 3/8-inch drive torque wrench is sometimes needed for accessing the smaller bolts and fasteners in the exhaust system.

  • Lower torque range (e.g., 5-80 ft-lbs)
  • Click-type mechanism for accurate readings
  • Compact design for tight spaces
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets is required to fit the various bolt and nut sizes used in the exhaust system.

  • Variety of sizes (e.g., 10mm, 13mm, 15mm, 17mm)
  • 6-point sockets for better grip
  • Durable construction
Learn more

Universal Joint or Extension

To access bolts that are in awkward or hard-to-reach positions, a universal joint or socket extension may be necessary.

  • Flexible joint to reach odd angles
  • Various lengths of extensions available
Learn more
Service Procedures

Exhaust System Bolt Torque Procedure

This procedure outlines how to properly torque exhaust system bolts on a 2019-Present Audi S8, ensuring a secure and leak-free seal.

  • Identify the location and size of the exhaust bolts requiring torquing.
  • Consult the torque specifications for each specific bolt. (Typical torque values are 25-30 Nm for most manifold nuts, 45-50 Nm for flange bolts, but always double check.)
  • Select the appropriate socket size and torque wrench.
  • Ensure the bolt threads are clean and free of damage. Apply anti-seize if needed.
  • Place the socket on the bolt head and attach the torque wrench.
  • Set the torque wrench to the specified torque value.
  • Torque the bolt in a smooth and controlled manner, listening for the click indicating the set torque has been reached. For multi-bolt flanges, tighten in a diagonal or star pattern.
  • Recheck the torque of each bolt once all bolts in the assembly are tightened to specifications.
  • If a gasket is involved, make sure the gasket is properly aligned. Replace gasket if damaged.
  • Perform a final inspection for any signs of leaks.
View full procedure

Exhaust Manifold Bolt Torque Procedure

Specific procedure for tightening exhaust manifold bolts.

  • Clean the manifold and cylinder head mating surfaces.
  • Inspect the exhaust manifold gasket for damage and replace if necessary.
  • Install the exhaust manifold and the new gasket onto the cylinder head.
  • Install the bolts by hand ensuring a proper fit.
  • Using a torque wrench tighten the manifold bolts in a diagonal or star pattern.
  • Torque to 25 Nm, re-check, and then torque to a final specified value. Note: This value may vary so always consult your service manual. (Typically 28-30 Nm)
  • Recheck the torque after the engine is up to operating temperature.
View full procedure
Technical Service Bulletins

Exhaust Bolt Loosening and Vibration Issues

2021-05-15

Some 2019-2021 Audi S8 vehicles have reported experiencing issues with exhaust system bolts loosening over time, potentially due to excessive vibration. This can lead to exhaust leaks and increased noise.

2019-2021 Audi S8

Resolution: Inspect exhaust bolt torque and use a high temp thread locker on reinstall. Also check exhaust system hangers for excessive wear or damage.

Exhaust Flange Gasket Deterioration

2022-11-20

Certain exhaust flange gaskets on the 2020-2022 Audi S8 have shown signs of premature deterioration, leading to exhaust leaks and loose bolts. Replacing gaskets during exhaust maintenance is recommended.

2020-2022 Audi S8

Resolution: Replace the original gaskets with updated heat-resistant gaskets and use the recommended torque specification during installation.

Revised Exhaust Bolt Torque Specifications

2023-07-10

Audi has revised the exhaust manifold bolt torque specifications for 2023 Audi S8 models. The new torque is now 30Nm. Previously it was 28Nm

2023 Audi S8

Resolution: Apply the updated torque specifications when installing exhaust manifold bolts on 2023 Audi S8 models.

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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