Volvo Volvo S90 1997-1998 Exhaust System Bolt Torque Specifications & Gasket Sealing
Volvo Volvo S90 1997-1998

Volvo Volvo S90 1997-1998 Exhaust System Bolt Torque Specifications

Detailed exhaust bolt torque specifications for the 1997-1998 Volvo S90, including recommended torque values and tightening procedures.

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

Exhaust Manifold Headers

Components that connect the exhaust manifold/headers to the engine block and cylinder head, ensuring a proper seal to prevent exhaust leaks.

1

Exhaust Manifold/Headers to Engine Block Bolts

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Ensure bolts are tightened in a cross pattern to evenly distribute pressure.
2

Exhaust Manifold/Headers to Cylinder Head Bolts

M8 x 1.25
Torque Value
16 ft-lbs (22 N·m)
Important Notes
Ensure bolts are tightened in a cross pattern to prevent warping.

Exhaust Pipes

Components that connect the exhaust manifold/headers to the catalytic converter, muffler, and other exhaust system parts.

1

Exhaust Pipe to Exhaust Manifold/Headers Bolts

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Ensure bolts are tightened evenly to prevent leaks.
2

Catalytic Converter to Exhaust Pipe Bolts

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Ensure bolts are tightened evenly to maintain emission control efficiency.
3

Muffler to Exhaust Pipe Bolts

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Ensure bolts are tightened evenly to reduce noise and maintain flow.

Exhaust Support

Components that secure the exhaust system to the vehicle's chassis or body, preventing excessive movement and potential damage.

1

Exhaust Hanger Bolts

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Ensure bolts are tightened securely to prevent movement.
2

Exhaust Heat Shield Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Estimated torque value based on M6 bolt size. Ensure heat shield is securely mounted.

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 is the recommended torque specification for the exhaust manifold bolts on a 1997-1998 Volvo S90?

The recommended torque specification for the exhaust manifold bolts on a 1997-1998 Volvo S90 is 25 Nm (18 lb-ft). Ensure the bolts are tightened in a crisscross pattern to evenly distribute the pressure.

Q2

How often should I check the exhaust system bolts for tightness?

It is advisable to check the exhaust system bolts every 10,000 miles or whenever you notice unusual noises, vibrations, or exhaust leaks. Regular inspections help prevent loosening due to thermal cycling.

Q3

Can I reuse old exhaust bolts, or should they be replaced?

Exhaust bolts are subject to high heat and stress, which can cause them to degrade over time. It is recommended to replace them with new bolts and washers to ensure proper sealing and prevent leaks.

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 precision tool for applying specific torque to bolts.

  • Adjustable torque settings
  • Calibrated for accuracy
Learn more

Socket Set

A set of sockets for use with a torque wrench.

  • Metric sizes
  • Durable construction
Learn more

Exhaust Gasket

Replacement gasket for the exhaust system.

  • Heat-resistant material
  • Proper sealing
Learn more
Service Procedures

Exhaust Bolt Torque Application

Procedure to properly torque exhaust system bolts on a 1997-1998 Volvo S90.

  • Remove the old exhaust system components, including bolts and gaskets.
  • Clean the exhaust manifold and mating surfaces thoroughly.
  • Install a new exhaust gasket in the correct position.
  • Hand-tighten the new exhaust bolts to ensure alignment.
  • Use a torque wrench to apply the specified torque to each bolt in a crisscross pattern to ensure even pressure.
  • Double-check torque settings and ensure all bolts are secure.
View full procedure
Technical Service Bulletins

Exhaust Bolt Fracture Issue

1998-03-15

Some 1997-1998 Volvo S90 models may experience fractures in exhaust bolts due to improper torque application.

1997-1998 Volvo S90

Resolution: Replace fractured bolts with new ones and ensure proper torque application using a calibrated torque wrench.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

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