DMF Troubleshooting
DMF Troubleshooting

DMF Troubleshooting

As a key component of a standard transmission’s clutch assembly, the dual mass flywheel (DMF) helps improve driver comfort, as well as increasing vehicle efficiency. In this technical article, Valeo offers technicians some troubleshooting tips to help diagnose damage, fault and wear.

Firstly, it is important to ascertain that the correct DMF is fitted in accordance to the vehicle’s engine code, and to extract any flash codes or engine faults. The next step is to check that all relevant vehicle systems are operating correctly to confirm they are not the cause. When all checks have been carried out to eliminate any other potential causes, the DMF can be removed and analysed in more detail for signs of fault and wear.

Perception – DMF fails, noise

Problem – Discoloured bluepurple colour on both sides, and/or visible damage

Cause – Very high thermal load


Perception – Noise or impaired starter operation

Problem – Secondary flywheel scores the primary flywheel

Cause – DMF bearing/bushing is worn out

Perception – DMF fails

Problem – Grease egress, sealing cap missing or discoloured brown due to overload

Cause – Thermal overload or mechanical damage/overload

Perception – DMF malfunction, noise

Problem – Burnt residues of abraded lining inside ventilation holes

Cause – Slippage and high thermal load

Perception – Loud humming, vibration

Problem – Balance weight missing (possible to see welding spots)

Cause – Mechanical impact on balance weight

Perception – Frequent noise and difficulty in changing gear

Problem – Folded or incorrectly fitted dowel pins

Cause – Mechanical damage

Perception – Noise when starting the engine

Problem – DMF ring starter gears heavily worn or broken

Cause – Defective starter

Perception – DMF fails

Problem – Strong noise and no torque transmission, Secondary flywheel is blocked or free to rotate at 360˚

Cause – Mechanical damage

Perception – DMF malfunction, friction noise

Problem – Trace of liquid or solid grease from primary flywheel welding

Cause – Defective primary flywheel

Perception – DMF fails

Problem – DMF bearing is damaged

Cause – Wear and/or mechanical impact

Perception – Noise and vibration

Problem – Secondary flywheel free to rotate beyond permissible free movement

Cause – Springs’ loss of effectiveness

For more information about the technical support and range of products available from Valeo, click here.

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