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Ask Mike Kelly Your Own Question
Mike Kelly
Mike Kelly, Auto Service Technician
Category: Car
Satisfied Customers: 5471
Experience:  17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.
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I have a mazda 6 diesel estate which has a knocking sound was

Customer Question

I have a mazda 6 diesel estate which has a knocking sound was told it was drive belt tensioner fitted new one still knocking when I switch aircon on it goes quiet can you tell me whats wrong is it the ac pump
Submitted: 4 years ago.
Category: Car
Expert:  Mike Kelly replied 4 years ago.
Hi,my name is mike and I will assist you with your question.
Since the noise goes away when the a/c is turned on,the noise that you are hearing is the shaft bearing inside of the a/c pump. The reason that you hear the noise with the a/c off is because the shaft is spinning much slower and the bearing makes a louder noise. To fix this issue the a/c pump has to be replaced.