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Common causes of camshaft timing belt failure on the above vehicles are due to incorrect operating tension, or ingress of dirt, water, or debris entering the timing belt cover. Predominantly on Fiesta models a high percentage of camshaft timing belt failures occur after the ancillary poly ‘V’ drive belt has failed, where strands of material off the broken belt have entered the timing belt cover. This is especially so where an ancillary belt has been fitted that does not contain “Kevlar” based materials. It is therefore important to always remove the timing belt cover to check for belt debris if the ancillary belt has failed. Any contamination that enters the timing belt cover can become compressed between the surfaces of the camshaft timing belt and drive pulleys. This causes wear to both the belt teeth, backing surface, and damage to the drive pulleys, resulting in premature failure of the camshaft timing belt. Later engines have modifications to improve the sealing of the belt cover around the crankshaft pulley, to reduce the level of outside contamination. Incorrect tensioning of the belt during installation will adversely affect the life of the belt. Before fitting a new belt it is important to check and observe the following points :- 1) Right Hand Inner Wing Splash Shield (Fiesta, Escort, Mondeo) This must be fitted and undamaged. 2) Timing Belt Cover Check that all components of the cover are fitted and undamaged. Ensure the latest type of modified cover is fitted. 3) a) Toothed Drive Pulleys Check that the tooth profiles are not worn or damaged. On vehicles built before January 1994 special attention should be given to the nylon toothed pulley situated below the camshaft pulley in a clockwise position on the belt drive (see diag item 4). This should be changed to a modified steel pulley (Ford No. 7053802) plus bolt (6701537). Ensure that the Camshaft and Injection Pump sprockets are free to rotate on the drive locations when the retaining bolts are slackened off. b) 4) a) b) c) Water Pump, Idler and Tensioner Pulleys Check that the belt running surfaces are not worn or damaged. Check that the flanges are running true and not damaged. Check that the water pump, and pulley bearings are in good condition, to ensure correct belt alignment. 5) Crankshaft Pulley The toothed pulley is in two parts. The rear section (Injection Pump Drive) is located onto the crankshaft by a small drive pin. The front section (Camshaft and “Poly V” belt drive) engages onto the rear pulley via a small vee protrusion on the rear face. Should the central fixing bolt for the crankshaft pulley come loose, or an old bolt re-used (Stretch bolt design), it is possible for fretting to take place damaging the locations. The crankshaft and camshaft pulleys can then move out of timing alignment, resulting in valve and piston contact damage. Replacement Procedure As the vehicle is fitted with two timing belts, one to drive the Camshaft, and one to drive the Injection Pump drives, which are driven off the crankshaft pulley, it is strongly recommended that both belts are replaced at the same time. NOTE: Special tools are required to lock the crankshaft, camshaft, and injection pump in the correct angular location when changing the belts, to ensure correct timing position. IMPORTANT: Ensure the engine is cold (not run for 4 hours) before commencing working as this will affect the setting of the timing belt tension and could lead to premature failure. Continued . . . .