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Robert, Renault Technician
Category: Renault
Satisfied Customers: 4534
Experience:  Fully qualified 19+yrs exp/self employed technician in the UK
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new timing belt kit ,dephaser,water pump fitted, a week later

Customer Question

new timing belt kit ,dephaser,water pump fitted, a week later something failed resulting in bent valves. Everything is still ok including belt what could have happened?
Submitted: 3 years ago.
Category: Renault
Expert:  Robert replied 3 years ago.



Hopefully i can help..


Certainly sounds like the lower crank pulley wasnt torqued up enough..this would have had to be removed after the engine was locked up or timing set to replace the belt - if that lower pulley wasnt tight enough this could well have cause the engine to loose its timing and thus the pistons would clash with the pistons..however the only way the valves can come into contact with the pistons after all work done above for example. - is either :- improper fitting / a mistake made in the alignment in regards XXXXX XXXXX engine upto to tdc and getting all marks aligned using timing pin and timing setting bar for both top cams / one of those pulleys - tensioner or guide pulley above if not replaced thus may have failed / or inproper tightening of the two top pulleys nuts and or the lower crank pulley bolt as they are known as floating pulleys so no key way - thats why it critical those 3 areas are upto the correct torque spec/thread locking compound especially the lower crank pulley - as if the lower bolt isnt tight enough you run the risk of causing valve to piston damage as it the bottom pulley that holds the lower timing belt crank sprocket in place to stop i moving out of alignment - all camshaft top nuts need to be renewed aswell as the lower bolt needs to be renewed...thats about the only way i can think off that may have caused this..i do hope this helps..I if you need to ask anything else or include anything further then just continue before you rate

Customer: replied 3 years ago.

bottom pulley was the only thing that was'nt replaced as it is not part of any kit.Should yhis still have been checked before new parts were replaced.

Expert:  Robert replied 3 years ago.

Hi..there thanks for your reply..


No bottom pulley doesnt get replaced usually nor the lower sprocket - its only removed the lower crank pulley that the auxillary belt runs over and re-installed "new bolt" when the belt is refitted..its generally that lower pulley bolt that needs to be torqued right upto the specific setting..if not then the pulley can work loose and cause the timing to shift at the crank hence the piston to valve damage if it works loose..thats about the only reason this could have happened..I do hope this helps above anything else you need to ask or info to include then just continue before you rate.

Expert:  Robert replied 3 years ago.



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