Subaru Subaru Impreza 2007-2011 Emissions & Sensor Bolt Torque Specifications
Subaru Subaru Impreza 2007-2011

Subaru Subaru Impreza 2007-2011 Emissions & Sensor Bolt Torque Specifications

Detailed bolt torque specifications for emissions sensors on the 2007-2011 Subaru Impreza, including oxygen sensors, EGR valves, and catalytic converter fasteners.

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

Egr System

The EGR system reduces nitrogen oxide emissions by recirculating a portion of exhaust gases back into the engine's intake manifold. Proper torque ensures a secure seal and prevents leaks.

1

EGR Valve Bolts

M8 x 1.25
Torque Value
20.5 ft-lbs (27.8 N·m)
Important Notes
Torque value is the midpoint of the provided range (18-23 ft-lbs).

Exhaust Manifold System

The exhaust manifold collects exhaust gases from the engine cylinders and directs them to the exhaust system. Proper torque ensures a leak-free connection.

1

Exhaust Manifold/Headers Bolts

M10 x 1.5
Torque Value
29.5 ft-lbs (40 N·m)
Important Notes
Torque value is the midpoint of the provided range (25-34 ft-lbs).
2

Exhaust Manifold/Headers to Cylinder Head Bolts

M8 x 1.25
Torque Value
20.5 ft-lbs (27.8 N·m)
Important Notes
Torque value is the midpoint of the provided range (18-23 ft-lbs).

Exhaust Pipe System

The exhaust pipe system connects the exhaust manifold to the catalytic converter and other downstream components. Proper torque ensures a tight seal and prevents exhaust leaks.

1

Exhaust Pipe to Exhaust Manifold/Headers Bolts

M10 x 1.5
Torque Value
29.5 ft-lbs (40 N·m)
Important Notes
Torque value is the midpoint of the provided range (25-34 ft-lbs).
2

Catalytic Converter to Exhaust Pipe Bolts

M8 x 1.25
Torque Value
14 ft-lbs (19 N·m)
Important Notes
Torque value is the midpoint of the provided range (13-15 ft-lbs).

Emissions Sensors

Emissions sensors monitor exhaust gas composition and temperature to ensure compliance with emissions standards. Proper torque ensures accurate readings and prevents leaks.

1

Oxygen Sensor (O2 Sensor)

M18 x 1.5
Torque Value
35 ft-lbs (47.5 N·m)
Important Notes
Torque value is estimated based on similar sensor specifications.
2

Air Fuel Ratio (AFR) Sensor

M18 x 1.5
Torque Value
35 ft-lbs (47.5 N·m)
Important Notes
Torque value is estimated based on similar sensor specifications.
3

Exhaust Gas Temperature (EGT) Sensor

M12 x 1.25
Torque Value
17.5 ft-lbs (23.7 N·m)
Important Notes
Torque value is the midpoint of the provided range (15-20 ft-lbs).

Heat Shield System

The heat shield protects the catalytic converter and surrounding components from excessive heat. Proper torque ensures the heat shield remains securely in place.

1

Catalytic Converter Heat Shield Bolts

M6 x 1.0
Torque Value
8 ft-lbs (10.8 N·m)
Important Notes
Torque value is the midpoint of the provided range (7-9 ft-lbs).

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 oxygen sensor on a 2007-2011 Subaru Impreza?

The recommended torque specification for the oxygen sensor (emissions sensor) on a 2007-2011 Subaru Impreza is typically 33-40 Nm (24-30 ft-lbs). Always refer to the vehicle's service manual for the exact specification, as variations may exist depending on the sensor's location (upstream or downstream).

Q2

Can I reuse the emissions sensor gasket or washer?

It is not recommended to reuse the gasket or washer on emissions sensors. These components are designed to create a proper seal during installation, and reusing them can lead to leaks or improper torque readings. Always replace them with new parts to ensure optimal performance.

Q3

What happens if I over-torque the emissions sensor?

Over-torquing the emissions sensor can damage the sensor's threads, the exhaust manifold, or the catalytic converter. This can lead to exhaust leaks, improper sensor readings, and costly repairs. Always use a torque wrench to ensure the correct torque is applied.

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

Digital Torque Wrench

A precision tool for applying the correct torque to emissions sensor bolts.

  • Adjustable torque settings
  • Digital display for accurate readings
Learn more

Oxygen Sensor Socket

A specialized socket designed for removing and installing oxygen sensors.

  • Cut-out design for sensor wiring
  • Durable construction for repeated use
Learn more

Thread Sealant

High-temperature thread sealant to prevent leaks at sensor connections.

  • Resistant to exhaust heat
  • Ensures a secure seal
Learn more
Service Procedures

Replacing the Front Oxygen Sensor

Step-by-step guide to safely remove and install the front oxygen sensor.

  • Disconnect the negative battery terminal.
  • Locate the front oxygen sensor near the exhaust manifold.
  • Use an oxygen sensor socket to remove the old sensor.
  • Apply thread sealant to the new sensor's threads.
  • Install the new sensor and torque to 30-40 ft-lbs.
  • Reconnect the sensor wiring and battery terminal.
View full procedure

Replacing the Rear Oxygen Sensor

Procedure for replacing the rear oxygen sensor located near the catalytic converter.

  • Disconnect the negative battery terminal.
  • Locate the rear oxygen sensor near the catalytic converter.
  • Use an oxygen sensor socket to remove the old sensor.
  • Apply thread sealant to the new sensor's threads.
  • Install the new sensor and torque to 30-40 ft-lbs.
  • Reconnect the sensor wiring and battery terminal.
View full procedure
Technical Service Bulletins

Oxygen Sensor Failure Due to Contamination

2010-05-15

Reports of oxygen sensor failure caused by oil or coolant contamination.

2007-2011 Subaru Impreza

Resolution: Inspect for leaks and replace the sensor if contamination is found. Use thread sealant during installation to prevent future issues.

Check Engine Light Due to Faulty Oxygen Sensor

2009-08-20

Frequent check engine light activation caused by faulty oxygen sensor readings.

2007-2011 Subaru Impreza

Resolution: Diagnose the sensor using an OBD-II scanner and replace if necessary. Ensure proper torque during installation.

About the Author

Expert automotive knowledge and experience

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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