Knock in an OBS Chevy 5.7 L

Asked by GuruRS1CJ Feb 08, 2020 at 10:34 PM about the Chevrolet Silverado 1500

Question type: Maintenance & Repair

I have a 91 Chevy I am helping my son work on. It developed a knock and to
determine if it was in the motor or some other problem i pulled the belt and
started. Knock went away and truck runs fine. added the belt back and knock
is very pronounced on the front drivers side around the power steering
pump. Changed the Power steering pump and water pump while i had it
down. put all back together and knock is still there. No pulleys seemed loose
or worn. knock is very loud and goes up and down with RPM. thanks for any
help or if someone has seen this before.

2 Answers


Sounds like a bad pulley if the knock stops when you remove the belt

1 people found this helpful.

If you have an A.I.R. (Air Injection Reaction) pump it could be that. If you can safely use a mechanic's stethoscope with the engine running to check the accessories, I'd recommend doing that. Hope that helps! Jim

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