I have a 2000 blazer ls 4 Dr 2 wheel drive I've been trying to diagnose a whirring noise directly tied to rpms its coming from left side of engine sounds like it may be coming from a pulley alternator maybe? I had the alternator tested a month ago and it tested fine the thing thats got me stumped is the whirring noise goes away sometimes the first time I heard it was probably three months ago heard it one day and never heard it again until now it went away for a couple days now its back and it doesn't start right when the engine starts at least not noticeable only after warmed up and driving I don't know if its related but my abs has been acting up lately going off randomly at low speeds anyone here of anything like this?

 

clutch fan ? pull the belt and check for draging pulleys