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Ask Tom Your Own Question
Tom
Tom, ASE Certified Technician
Category: Chevy
Satisfied Customers: 25954
Experience:  Qualified to repair all makes and models.
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why my car has a loud knocking sound coming from underneath my car

Customer Question

why my car has a loud knocking sound coming from underneath my car
Submitted: 5 years ago.
Category: Chevy
Expert:  Tom replied 5 years ago.
Was this a salvage yard motor ? If so its most likely damaged from sitting or has water in it from siting. This needs the checked next . Happens a lot with salvage motors actually . You will get another motor no charge but it does not cover labor . Hoped this helped. Positive feedback and bonuses greatly appreciated.
Customer: replied 5 years ago.
It was not a salvage yard motor
Expert:  Tom replied 5 years ago.
This was a new crate motor ?
Customer: replied 5 years ago.
it was pulled out of my truck running perfect and everything was swapped over in one day but i just noticed that one of my rocker arms wont prime up
Expert:  Tom replied 5 years ago.
Ok that's a collapsed lifter issue . It's either not getting oil pressure or the lifter itself is damaged and needs to be replaced. These are what need to be checked next . Hoped this helped. Positive feedback and bonuses greatly appreciated.
Customer: replied 5 years ago.
would that cause the loud knocking and how do i fix that
Expert:  Tom replied 5 years ago.
Yes . You need to check oil pressure and the lifter itself . That would be the next step . Hoped this helped. Positive feedback and bonuses greatly appreciated.
Customer: replied 5 years ago.
is there any special steps to do this or what
Expert:  Tom replied 5 years ago.
No just an oil pressure gauge at the pressure switch and see if it's within specs. If not it can be an oil pump issue . Also you can physically check the lifter for damage.
Customer: replied 5 years ago.
i check the car today and stuck my hand on top of the distributor and it felt as if it was grinding in the inside as it rotates inside with the car running
Expert:  Tom replied 5 years ago.
Yes that can be the cause of the noise. The bearings in these distributors fail and cause this issue. I would start here next. Hoped this helped. Positive feedback and bonuses greatly appreciated.
Customer: replied 5 years ago.
Should I replace the distributor
Expert:  Tom replied 5 years ago.
Yes absolutely .