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Hello. Welcome to Just Answer. Please allow me to assist you. This sounds very much like a problem I had in the shop several years ago. To make a long story short, the replacement pumps (we tried 5) had the incorrect length stroke arms fitted. I would look to see if the pump that you took off initially is the exact same length. Exact Same length is critical. Even 3/3" would cause this noise, as it did in our case. Hope this helps.