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Mark, Renault Certified Technician
Category: Renault
Satisfied Customers: 1504
Experience:  Fully qualified technician and MOT tester
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Changing timing belt crankshaft sprocket has come loose,there

Customer Question

changing timing belt crankshaft sprocket has come loose,there appears to be no locking key although there is a key way in the crank.two questions
1. is there a locking plate which is missing?
2. how is the sprocket secured in the correct place on the crank?
Submitted: 2 years ago.
Category: Renault
Expert:  Mark replied 2 years ago.
Hello, my name is ***** ***** I will try help you with this.
There is no locking key for the crank sprocket. It sits on a tapered shaft and is locked by friction when the crank pulley bolt is tightened.
When replacing the belt you have to use tools designed to lock the camshafts in place and a locking pin to set the crankshaft position through the engine block.
The reason the crank pulley can move is to allow for the correct tensioning of the timing belt. When you tighten the belt, the pulley turns slightly but the crank does not move.
If you have allowed the crank or cams to move because you did not use the proper tools to lock them in place then you need to be very careful in the way you reset the engine before fitting the timing belt. Getting it wrong can result in you bending the valves or damaging the pistons.