Lock washer a necessity on idler pulley?

[Shawn_248]

I took my belt off and spun all the pulleys to see where my noise was coming from, and it was the idler pulley. I took the old one off and the lock washer had to be cut off with a dremel tool, and I got the new one on. I'm positive I got it on tight as it'd go, so do I have to have that lock washer? I'm pretty sure it won't work it's way loose

 

[AllanD]

The "lock washer" is more of a "bolt retainer", an assembly aid to keep the bolt together with the pulley before installation on the engine.

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