By May 23, 2012 Read More →

Rattling Noise Under Car

I have a Chevrolet Blazer with a vortec 4.3L v6. when it is idling there is a loud rattling sound from underneath it. It sounds like it may be coming from the engine itself. Any ideas what it might be?


Hey there,

I would first inspect the fan belt tensioner, and see if it is flopping around. With the engine running (and the noise present) open the hood and look at the fan belt, is there anything flopping around, or is the belt running smooth and tight?

I would also turn the ac compressor on and off with the engine running to see if the noise comes and goes due to a bad compressor or compressor clutch/pulley.

With the engine OFF, grab the plastic fan blade with both hands and see if you can move it up and down and side to side. If you can, you might have a bad water pump or fan clutch.

I have also heard a rattle noise coming from a bad catalytic converter. Get under the vehicle with the engine running and listen to the converter in the exhaust pipe to see if the noise is coming from there.



Austin Davis

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."

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