A DMF can also be checked while fitted in the vehicle or once removed using the special dual-mass flywheel test tool. Here, the free travel of the torsional damper, the evenness of its spring force, the axial bearing conditions and the displacement travel of the radial bearing site can be determined.
The dual-mass flywheel test tool is designed only for dual-mass flywheels manufactured by ZF. Dual-mass flywheels from other manufacturers cannot be assessed with the scope of supply and the included instructions. The test tool allows you to easily check a run-in dual-mass flywheel (DMF) that is fitted to the vehicle or has been removed. Checks can be done, for example, on the free travel of the torsional damper, the evenness of its spring force, the axial bearing conditions and the displacement travel of the radial bearing site.
Note: Determining the current condition of the dual-mass flywheel does not allow any reliable conclusions to be drawn regarding the remaining service life.
When checking the free travel of the torsional damper, the secondary part of the DMF is rotated using the lever counterclockwise until encountering slight counterpressure or feeling the spring force of the torsional damper. The free travel should not be more than six teeth of the starter ring gear. If it is more than six teeth, it is highly likely that internal damage exists and the DMF will need replacing.
When checking the axial bearing site, the secondary part of the DMF is moved evenly to and fro using the lever within the clearance. If the secondary part rubs on the primary side and/or scraping noises can be heard, the DMF will need replacing.
Note: The tilt of the secondary part does not provide any indication of the condition of the DMF; this may be larger or smaller due to the design.
To check the spring force of the torsional damper, the secondary part of the DMF is increasingly rotated right and left against the spring force of the torsional damper in both directions using the lever. The spring force should be noticeable during the check in both directions and with an evenly increasing force. Grinding or scraping noises are indicative of a defect – the DMF will need replacing.
The radial bearing site is checked by pressing the secondary part of the DMF lightly and evenly using the lever, while trying to move it radially by applying light force. During testing, no or only a slight radial clearance should be discernible. In the event of large radial displacement, the DMF must be replaced.