My chevy 98 Blazer , had new motor mounts, now it is making a noise like a fan hitting something ,?

another mechanis did a OBD, and it came back vac . could that make that kind of noise , or is it a engine problem, when I am driving on the highway it is fine ,just when I am slowing down and taking off . the mechanic should make good cause it was not doing it before , but he wont , I hope the motor aint going , sounds like a fan, hitting something I checked the big engine fan, Hmm, thank you for the help