knock knock under the hood

Asked by Giovanni Sep 16, 2017 at 09:02 AM about the 2005 Chevrolet Trailblazer EXT LT 4WD

Question type: Maintenance & Repair

I've got a slight knock in my trailblazer. I've
heard a number of things, such as the fan
clutch, the serpentine belt. Where I
remember, if you hear a knock it's in your
block. Is this an easy repair or what should I
do with it?

157,425

Bob answered 6 years ago

Remove the serpentine belt and "briefly" start your engine. If the knock is gone the tensioner is the likely suspect. If the knock remains it is possibly an engine issue such as a rod bearing or a camshaft valve train issue, You may need to replace the engine is the knock is from any internal parts. Exhaust leaks from loose or cracked exhaust manifolds can sometimes sound like a knock.

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