Mercedes-Benz Mercedes CLS 2018-present Emissions & Sensor Bolt Torque Specifications
Mercedes-Benz Mercedes CLS 2018-present

Mercedes-Benz Mercedes CLS 2018-present Emissions & Sensor Bolt Torque Specifications

Detailed torque specifications for the emissions sensors on the 2018-Present Mercedes-Benz CLS. Includes precise values and installation guidelines.

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 And Headers

This subsystem includes components that manage exhaust gas flow from the engine to the exhaust system. Proper torque ensures a tight seal to prevent leaks, which could affect emissions sensor accuracy and overall emissions performance.

1

Exhaust Manifold/Headers Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Ensure bolts are tightened in a crisscross pattern to evenly distribute pressure.
2

Exhaust Manifold/Headers to Cylinder Head Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Use a crisscross pattern to ensure even sealing pressure.

Exhaust Pipe And Catalytic Converter

This subsystem includes components that connect the exhaust manifold to the catalytic converter and downstream exhaust system. Proper torque ensures a secure connection and prevents exhaust leaks.

1

Exhaust Pipe to Exhaust Manifold/Headers Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Ensure gasket is properly aligned before tightening.
2

Catalytic Converter to Exhaust Pipe Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Ensure gasket is properly aligned before tightening.

Emissions Control Components

This subsystem includes critical emissions control components such as the EGR valve, oxygen sensors, NOx sensors, DPF, and SCR system. Proper torque ensures secure mounting and prevents leaks that could affect emissions sensor accuracy.

1

EGR Valve Bolts

M6 x 1.0
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Ensure gasket is properly aligned before tightening.
2

Oxygen Sensor (Lambda Sensor) Mounting

M18 x 1.5
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Estimated value based on similar sensor mounting specifications.
3

NOx Sensor Mounting

M18 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Estimated value based on similar sensor mounting specifications.
4

DPF (Diesel Particulate Filter) Mounting Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Ensure gasket is properly aligned before tightening.
5

SCR (Selective Catalytic Reduction) System Mounting Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Ensure gasket is properly aligned before tightening.

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 emissions sensors on a 2018-Present Mercedes CLS?

The recommended torque specification for the emissions sensors on a 2018-Present Mercedes CLS is typically 25 Nm (18.4 lb-ft). However, always refer to the vehicle's service manual or manufacturer guidelines for the exact specifications, as they may vary depending on the specific sensor or model year.

Q2

Can over-tightening the emissions sensors cause damage?

Yes, over-tightening the emissions sensors can damage the sensor threads or the mounting point on the exhaust system. This can lead to leaks, sensor malfunction, or costly repairs. Always use a calibrated torque wrench to ensure proper tightening.

Q3

How often should emissions sensors be inspected or replaced?

Emissions sensors should be inspected during routine maintenance, typically every 30,000 to 50,000 miles. If the vehicle's check engine light is on or there are signs of poor performance or increased emissions, the sensors should be checked immediately. Replacement intervals vary but are often around 100,000 miles.

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

Torque Angle Gauge

Used to measure the angle of rotation when tightening bolts to ensure proper torque.

  • Angle measurement up to 360 degrees
  • Magnetic base for easy attachment
Learn more

Thread Locking Compound

A chemical compound applied to bolt threads to prevent loosening due to vibrations.

  • High-temperature resistance
  • Prevents corrosion
Learn more
Service Procedures

Emissions Sensor Bolt Torque Application

Detailed steps for applying the correct torque to emissions sensor bolts on a 2018-Present Mercedes CLS.

  • Ensure the vehicle is on a flat surface and the engine is cool.
  • Locate the emissions sensor and identify the bolts requiring torque application.
  • Clean the bolt threads and apply a small amount of thread locking compound.
  • Using a digital torque wrench, tighten the bolts to the manufacturer's specified torque value (e.g., 25 Nm).
  • Use a torque angle gauge to apply the specified angle of rotation (e.g., 90 degrees) after reaching the initial torque value.
  • Double-check the torque and angle settings to ensure proper installation.
View full procedure
Technical Service Bulletins

Emissions Sensor Bolt Loosening Issue

2021-05-15

Reports of emissions sensor bolts loosening over time due to insufficient torque application.

2018-2022 Mercedes CLS

Resolution: Ensure proper torque and angle specifications are followed during installation. Use a thread locking compound to prevent loosening.

Incorrect Torque Specifications in Service Manual

2020-11-10

Service manuals for certain models contained incorrect torque specifications for emissions sensor bolts.

2018-2020 Mercedes CLS

Resolution: Refer to the updated torque specifications provided by Mercedes-Benz. Verify torque values with a digital torque wrench.

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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