Mercedes-Benz Mercedes CLA 2019-present Exhaust System Bolt Torque Specifications & Gasket Sealing
Mercedes-Benz Mercedes CLA 2019-present

Mercedes-Benz Mercedes CLA 2019-present Exhaust System Bolt Torque Specifications

Detailed torque specifications for the exhaust bolts on the 2019-Present Mercedes-Benz CLA, including proper tightening sequences and recommended tools.

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

This subsystem includes bolts that secure the exhaust manifold or headers to the cylinder head and exhaust pipe. Proper torque ensures a tight seal to prevent exhaust leaks, which can affect engine performance and emissions.

1

Exhaust Manifold/Headers to Cylinder Head Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a proper seal to prevent exhaust leaks into the engine bay.
2

Exhaust Pipe to Exhaust Manifold/Headers Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a tight connection to prevent leaks and maintain exhaust flow efficiency.

Exhaust Pipe Catalytic Converter

This subsystem includes bolts that connect the catalytic converter to the exhaust pipe. Correct torque ensures a secure fit, preventing leaks and maintaining proper exhaust flow and emissions control.

1

Catalytic Converter to Exhaust Pipe Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a secure fit to prevent leaks and maintain proper exhaust flow.

Exhaust Pipe Muffler

This subsystem includes bolts that secure the muffler to the exhaust pipe. Proper torque ensures a tight connection, preventing leaks and reducing exhaust noise.

1

Muffler to Exhaust Pipe Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a tight connection to prevent leaks and reduce exhaust noise.

Exhaust Hangers

This subsystem includes bolts that secure the exhaust system to the vehicle's underbody. Proper torque ensures the exhaust system is stable and prevents excessive movement, which can lead to stress fractures or leaks.

1

Exhaust Hanger Bolts

M8 x 1.25
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Ensure the exhaust system is stable and prevents excessive movement.

Oxygen Sensor

This subsystem includes bolts that secure the oxygen sensor to the exhaust system. Proper torque ensures a secure fit and prevents leaks, which could lead to inaccurate sensor readings and affect engine performance.

1

Oxygen Sensor (O2 Sensor) Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a secure fit to prevent leaks and maintain accurate sensor readings.

Exhaust Heat Shield

This subsystem includes bolts that secure the exhaust heat shield to the vehicle. Proper torque ensures they remain securely in place without over-tightening, which could damage the shield or mounting points.

1

Exhaust Heat Shield Bolts

M6 x 1.0
Torque Value
10 ft-lbs (14 N·m)
Important Notes
Ensure the heat shield remains securely in place without over-tightening.

Exhaust Flange

This subsystem includes bolts that connect sections of the exhaust system. Proper torque ensures a tight seal and prevents leaks at the joints.

1

Exhaust Flange Bolts

M10 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Ensure a tight seal at the joints to prevent leaks.

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 torque specification for the exhaust manifold bolts on a 2019-Present Mercedes CLA?

The torque specification for the exhaust manifold bolts on a 2019-Present Mercedes CLA is typically 23 Nm (17 lb-ft). However, always refer to the official Mercedes-Benz service manual for your specific model and engine type, as specifications may vary.

Q2

How often should I check the torque on my exhaust system bolts?

It is recommended to check the torque on exhaust system bolts during routine maintenance, such as every 30,000 miles or if you notice symptoms like exhaust leaks, rattling noises, or a drop in performance. Regular inspections help prevent issues caused by thermal expansion and vibration.

Q3

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

Exhaust bolts are often exposed to high temperatures and stress, which can cause them to weaken over time. It is generally recommended to replace them with new bolts during exhaust system repairs to ensure proper clamping force and prevent failures. Reusing old bolts may lead to leaks or stripped threads.

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 values to bolts.

  • Adjustable torque settings
  • Durable construction for automotive use
Learn more

Socket Set

A set of sockets compatible with exhaust system bolts.

  • Includes metric sizes
  • Deep sockets for hard-to-reach bolts
Learn more

Thread Locker

A chemical compound to secure bolts and prevent loosening.

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

Exhaust Manifold Bolt Torque Procedure

Detailed steps for correctly torquing exhaust manifold bolts on a 2019-Present Mercedes CLA.

  • Ensure the engine is cool before starting.
  • Remove any components obstructing access to the exhaust manifold.
  • Clean the bolt threads and apply thread locker if recommended.
  • Tighten the bolts in a crisscross pattern to the specified torque value.
  • Double-check torque settings with a calibrated torque wrench.
View full procedure

Exhaust Downpipe Bolt Torque Procedure

Steps for torquing exhaust downpipe bolts to prevent leaks and ensure proper sealing.

  • Inspect the downpipe and gasket for damage before installation.
  • Align the downpipe with the exhaust manifold and insert bolts.
  • Tighten bolts gradually in a star pattern to the specified torque.
  • Recheck torque after the engine has been run and cooled.
View full procedure
Technical Service Bulletins

Exhaust Bolt Loosening Issue

2021-05-15

Reports of exhaust bolts loosening over time due to thermal cycling.

2019-2023 Mercedes CLA

Resolution: Apply high-temperature thread locker and re-torque bolts to factory specifications.

Exhaust Manifold Cracking Due to Over-Torquing

2022-08-10

Over-torquing exhaust manifold bolts can lead to cracking and exhaust leaks.

2019-2023 Mercedes CLA

Resolution: Follow the manufacturer's torque specifications and use a calibrated 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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