Audi Audi A8 2010-2017 4.2L Engine Bolt Torque Specifications & Fastener Values
Audi Audi A8 2010-2017

Audi Audi A8 2010-2017 4.2L Engine Bolt Torque Specifications

Comprehensive guide to bolt torque specifications for the 4.2L engine found in the 2010-2017 Audi A8 (D4) model. Includes detailed torque values for various engine components.

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

Engine Block And Internals

Torque specifications for components within the engine block, including cylinder head, main bearing, connecting rods, and oil pan.

1

Cylinder Head Bolts (First Pass)

M12 x 1.75 (Estimated)
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Secures cylinder head to the engine block. Torque sequence required. Estimated bolt size.
2

Cylinder Head Bolts (Second Pass)

M12 x 1.75 (Estimated)
Important Notes
Final tightening of cylinder head bolts. Requires angle tightening after initial torque. Estimated bolt size.
3

Cylinder Head Bolts (Third Pass)

M12 x 1.75 (Estimated)
Important Notes
Final angle tightening for complete clamping. Estimated bolt size.
4

Main Bearing Cap Bolts (Inner Bolts)

M10 x 1.5 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures main bearing caps to engine block. Torque sequence is required. Estimated bolt size.
5

Main Bearing Cap Bolts (Outer Bolts)

M10 x 1.5 (Estimated)
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Provides additional clamping for main bearing caps. Torque sequence is required. Estimated bolt size.
6

Connecting Rod Bolts

M9 x 1.25 (Estimated)
Important Notes
Secures connecting rod to crankshaft. Requires angle tightening after initial torque. Torque sequence required. Estimated bolt size.
7

Oil Pan Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures oil pan to the engine block.
8

Oil Drain Plug

M14 x 1.5 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Seals the oil drain hole. Typically uses a crush washer. Estimated bolt size.
9

Flywheel/Flexplate Bolts

M12 x 1.5 (Estimated)
Important Notes
Secures flywheel (manual) or flexplate (automatic) to crankshaft. Requires angle tightening after initial torque. Estimated bolt size.
10

Crankshaft Pulley Bolt (Center Bolt)

M18 x 2.0 (Estimated)
Important Notes
Holds crankshaft pulley, use a new bolt. Requires angle tightening after initial torque. Estimated bolt size.

Valve Train

Torque specifications for components within the valve train system.

1

Camshaft Bearing Cap Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures camshaft bearing caps to cylinder head.
2

Valve Cover Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures valve covers to cylinder heads.

Intake And Exhaust

Torque specifications for intake and exhaust system components.

1

Intake Manifold Bolts

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Secures intake manifold to cylinder heads.
2

Exhaust Manifold Nuts/Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures exhaust manifold to cylinder head. Often uses copper nuts which are to be replaced upon each dis assembly.
3

Catalytic Converter Bolts

M8 x 1.25 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Fastens catalytic converter to exhaust system. Estimated bolt size.
4

Exhaust Flange Bolts

M8 x 1.25 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Connects exhaust pipes to each other. Estimated bolt size.

Cooling System

Torque specifications for cooling system components.

1

Water Pump Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures water pump to engine block.
2

Thermostat Housing Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures thermostat housing to engine.

Accessories

Torque specifications for engine accessories.

1

Alternator Mounting Bolts

M8 x 1.25 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures alternator to the engine. Estimated bolt size.
2

Power Steering Pump Bolts

M8 x 1.25 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures power steering pump to engine. Estimated bolt size.
3

Air Conditioning Compressor Bolts

M8 x 1.25 (Estimated)
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Secures A/C compressor to engine. Estimated bolt size.

Other And General

Torque specifications for miscellaneous and general application bolts.

1

Engine Mount Bracket Bolts

M10 x 1.5
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Secures engine mount brackets to engine block.
2

Transmission to Engine Bolts

M12 x 1.75 (Estimated)
Torque Value
59 ft-lbs (80 N·m)
Important Notes
Connects transmission to engine block. Estimated bolt size.
3

Ground Strap Bolts

M6 x 1.0 (Estimated)
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Provides secure electrical ground. Estimated bolt size.
4

M6 Bolts General Application

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Generic use where smaller bolts are present.
5

M8 Bolts General Application

M8 x 1.25
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Generic use where medium-sized bolts are present.
6

M10 Bolts General Application

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Generic use where larger bolts are present.

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 correct torque specifications so important for the 4.2L engine?

Using the correct torque specifications ensures proper clamping force, preventing leaks, component damage, and potential engine failure. For instance, over-tightening cylinder head bolts can distort the head and gasket, leading to coolant or oil leaks and potential overheating or compression issues. Under-tightening can lead to similar leakages and can also cause bolts to loosen during operation, leading to catastrophic engine damage.

Q2

What type of torque wrench should I use?

A calibrated torque wrench is essential. Click-type torque wrenches are common and effective for most applications. For critical components like cylinder heads, a digital torque wrench, which offers greater accuracy and is often angle-capable, is recommended. Always ensure your wrench is within its calibration period and suitable for the required torque range, for example some torque wrenches are unsuitable for the low torque requirements of the valve cover.

Q3

Should I use new bolts when reassembling engine components?

Yes, it is generally recommended to use new bolts, especially for critical components like cylinder head bolts and connecting rod bolts. Many of these bolts are designed to stretch when tightened and are intended for single use. Reusing them can lead to improper clamping force and increase the risk of failure. For example, reusing a cylinder head bolt that has been stretched can result in uneven head clamping and could cause the head gasket to fail.

Q4

What happens if I over-tighten a bolt on the 4.2L engine?

Over-tightening can cause the bolt to stretch or break, potentially stripping threads in the engine block or component. For instance, over-tightening an intake manifold bolt can crack the manifold or damage the mounting point. If the bolt breaks, removing the broken piece can be difficult and could require expensive repairs. Additionally, over-tightening can damage gaskets leading to leaks.

Q5

How do I know if a torque spec is in Newton-meters (Nm) or pound-feet (lb-ft)?

Torque specifications are usually denoted by the unit of measure (e.g., Nm or lb-ft). The repair manual for the 2010-2017 Audi A8 will specify which unit to use. Double check the manual and ensure your torque wrench is set to the correct units. Mistakes can lead to severe component damage. A common situation is a user incorrectly converting units and over-tightening components.

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" Drive)

A calibrated torque wrench is essential for achieving precise bolt torques, preventing over-tightening or under-tightening.

  • Wide torque range (e.g., 20-200 Nm)
  • Click-type or digital display
Learn more

Torque Wrench (3/8" Drive)

A smaller torque wrench for accessing smaller bolts and tighter spaces in the engine bay.

  • Smaller torque range (e.g., 5-60 Nm)
  • Click-type or digital display
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets in 1/2" and 3/8" drives is necessary to match various bolt head sizes.

  • Sizes ranging from 8mm to 24mm
  • 6-point and 12-point options
Learn more

Extension Bars

Various length extension bars to reach bolts in recessed areas or difficult angles.

  • 1/2" and 3/8" drive compatibility
  • Different lengths (e.g., 3", 6", 10")
Learn more

Universal Joint

A universal joint allows torque wrench application at angles when a straight shot is not possible

  • 1/2" and 3/8" drive compatibility
  • Swivel design
Learn more

Engine Repair Manual

The official repair manual provides detailed torque specifications specific to the 4.2L engine in the Audi A8.

  • Detailed torque specifications
  • Diagrams and illustrations
Learn more
Service Procedures

Cylinder Head Bolt Tightening

The procedure for properly tightening the cylinder head bolts, requiring precise torque and angle tightening steps.

  • Apply new cylinder head bolts.
  • First Stage: Torque all bolts to 40 Nm.
  • Second Stage: Torque all bolts to 60 Nm.
  • Third Stage: Angle tighten all bolts 90 degrees.
  • Fourth Stage: Angle tighten all bolts an additional 90 degrees.
View full procedure

Intake Manifold Bolt Tightening

Steps for proper tightening of intake manifold bolts to prevent leaks and ensure proper seal.

  • Torque all intake manifold bolts to 10 Nm.
  • Recheck torque in a crisscross pattern to 10 Nm.
View full procedure

Camshaft Bearing Cap Bolt Tightening

Procedure for securing camshaft bearing caps, crucial for camshaft alignment and performance.

  • Torque camshaft bearing cap bolts to 10 Nm.
  • Recheck torque in a crisscross pattern to 10 Nm.
View full procedure

Connecting Rod Bolt Tightening

Procedure for tightening the connecting rod bolts to ensure proper bearing and rod operation.

  • Apply new connecting rod bolts
  • First Stage: Torque all bolts to 20 Nm.
  • Second Stage: Angle tighten all bolts 90 degrees.
View full procedure

Crankshaft Main Bearing Cap Bolt Tightening

Procedure for properly tightening crankshaft main bearing cap bolts to support crankshaft stability.

  • Apply new crankshaft main bearing bolts
  • First Stage: Torque all bolts to 40 Nm.
  • Second Stage: Angle tighten all bolts 90 degrees.
View full procedure

Oil Pan Bolt Tightening

Proper procedure for tightening the oil pan bolts to prevent leaks.

  • Torque oil pan bolts to 25 Nm.
  • Recheck torque in a crisscross pattern to 25 Nm.
View full procedure
Technical Service Bulletins

Cylinder Head Bolt Re-Torque Procedure

2014-07-15

Some 2010-2013 models may exhibit minor oil leaks after cylinder head work. This bulletin outlines a re-torque procedure to rectify this issue.

2010-2013

Resolution: After initial torque procedure, allow engine to cool completely. Re-torque cylinder head bolts to 40 Nm, then angle tighten 20 degrees.

Connecting Rod Bolt Update

2016-03-22

A revised connecting rod bolt specification has been issued for 2014-2017 models, impacting torque angle.

2014-2017

Resolution: Apply new connecting rod bolts. First stage torque: 20 Nm. Second stage: Angle tighten 70 degrees.

Intake Manifold Bolt Sequence Clarification

2017-11-01

Updated information regarding specific tightening sequence for intake manifold bolts to ensure proper sealing and prevent vacuum leaks.

2010-2017

Resolution: Tighten all intake manifold bolts by hand until contact is made with intake manifold. Torque bolts in a circular motion going from the center bolt out to 10 Nm. Recheck torque in a crisscross pattern.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

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