Valeoscope Commercial Vehicles Clutch 2020

Diagnosis Clutch slippage or lack of torque capacity

3.2.2 Reasons due to the clutch 1. Over-heated spots on the pressure plate surface (creeping) Parts inspection ●● Over-heated spots on the pressure plate surface Vehicle behaviour ●● Clutch slippage ●● Burnt facing smell ●● Smoke emitted from the clutch housing

1. Blue-stained pressure plate

2. External reasons due to the clutch linkage: seized fork on ball pivot/axis

Clutch inspection Oxidized and seized fork on its axis Vehicle behaviour ●● Loss of transmission of the engine torque ●● Slippage

Parts inspection ●● The fork pivot is seized on the fork ●● The bushing is worn or broken

●● Linkage axis and links are seized, out of round Vehicle behavior ●● Wrong release, difficult gear shift ●● Slippage and accelerated wear of facings ●● Rough clutch engagement ●● Heavy pedal load during clutch engagement Reasons ●● The release bearing travel is not sufficient to release the clutch disc. ●● The release bearing movement is slowed down (increase of engagement time). ●● The release bearing movement cannot be precisely controlled, which means starting up is not smooth. ●● The fork is oxidized and seized on its axis. Attention Ɂ Ɂ In the case that there is a hard point or stick slip movement of linkage, it is necessary to maintain the linkage system or to check the clutch facings wear. Diagnosis ò ò No grease or not enough grease when assembled ò ò Not suitable grease ò ò Wrong status of fork linkage The diagnosis can be made by measuring the bearing travel or by observation through the clutch housing hole. Advice   Any part (ball pivot, axis, rod, yoke…) with seizing, rust or wear must be replaced to keep the good function of the clutch linkage and to ensure a clutch long life.  During re-assembly, it is necessary to apply suitable grease on any hinge.  We highly recommend changing the fork pivot each time of the clutch change.

Blue spots on the pressure plate

Parts inspection ●● Blue spots on the pressure plate, but no other damages ●● The pressure plate mass temperature reached 200°C Vehicle behavior Long time clutch slippage in low energy, mainly happens on driving up hills or in high engine torque. Reasons ●● Wrong conditions and wrong adjustments of the clutch linkage. ●● Seizing of the tube-guide. ●● Wrong bolting of cover assembly on the pressure plate. ●● The facings are totally worn out. ●● Breakage of the diaphragm. ●● Mistake in choosing the cover assembly (insufficient load). Diagnosis ò ò The pressure plate load has become insufficient and there is a delay of the pressure plate lift during engagement. Attention Ɂ Ɂ Always replace the 3 parts of the clutch kit. Advice   Check the clutch linkage conditions and make adjustments according to the manufacturer’s instructions.

Oxidized and seized fork on its axis

Reasons ●● Projections of water, when cleaning the vehicle. ●● Hatch opened. ●● No greased fork axis (see recommendations of the manufacturer). Advice  ą ą Make sure that the hatch is in place, and closed. ą ą Avoid splashing water during cleaning operations. ą ą Perform the necessary lubrication of the fork axis while preceding the re-assembly operation.

Creeping on the pressure plate surface

Reasons ●● Severe usage of the clutch (earth moving, vehicle stuck in mud, towing, overload, difficult start-up conditions, high grade roads…). ●● Vehicle is not used the way it has been designed for. Diagnosis ò ò The pressure plate material has been transformed in some spots = metal creeping. ò ò The pressure plate surface temperature has reached 700°C or more. Attention Ɂ Ɂ A vehicle stuck in mud must be towed. Advice   Choose the vehicle according to most severe usage conditions (engine, driveline).  Watch their usage in severe situations and avoid wrong operating behavior.  Always replace the 3 parts of a clutch kit.

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