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Knocking from some pulley?

Knocking from some pulley?

Postby joshkeast [OP] » Mar 08 2011, 8:05am

Hi there everybody.

Just got my 5.7 Vortec running again after a valve job. Now I can hear a knocking sound coming from the front of the engine. When I take the belt off and run the engine, there is no noise. I also drove about 15 miles and the knocking stopped but 15 miles back home and it was doing it again. I thought it might be the tensioner so I put a brand new one on, still knocked, so put the original back on, thought it might be the new water pump so I put the original back on, still knocks. I noticed the fan has a very slight wobble to it, not enough to hit the fan shroud. I'm thinking maybe the bearings on the idler pulley are maybe going bad... What do you guys think?

Thanks in advance.
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Related Topics  Idler pulley/ alternator   Pulley Squeal, have video.   Alternator pulley bearing bad?   knocking noise   Knocking After Shut-Off   knocking sound, comes and goes   2005 silverado 5.3 knocking   Knocking sound in transmission   Knocking when foot is taken off of gas   low oil pressure no knocking   Front knocking/popping sound   Low Oil Pressure and Knocking   07-13 Silverado Exhaust Leak/Knocking   Knocking in steering column in turns 
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Re: Knocking from some pulley?

Postby Levman74 » Mar 08 2011, 9:03am

The fan clutch would be my first guess, had one go bad on me too, sometimes the seal leaks oil and it develops issues. Pull the clutch off and try that, test...test...test...
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Re: Knocking from some pulley?

Postby joshkeast [OP] » Mar 08 2011, 10:23pm

Ok well it's not the idler pulley. Just put a new one on (it looked like it needed replaced anyway, had a groove worn into it). The knock isn't as loud as it was before, it's more like a tic now, I don't know if it's because I replaced the idler pulley or if it's because i've driven it about 100 miles now. One suggestion from a buddy of mine was that it could be a bad harmonic balancer. I destroyed the original one trying to take it off with the wrong puller so we put one on that was originally for my brothers demo car but never got installed. I notice a very slight wobble on the crank pully. I'm getting a mechanics stethescope tomorrow.

One thing that's got me stumped is the tic noise is very rythmic. It tics at the same spot on every revolution.
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Re: Knocking from some pulley?

Postby joshkeast [OP] » Mar 08 2011, 11:19pm

I just checked the fan clutch, which checked fine, but then i remembered, It started knocking before I even put the fan on it so I know it not the fan or clutch posing problems. How would you check if the alternator, power steering pump or air conditioner compressor pulleys are going bad?
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joshkeast
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Re: Knocking from some pulley?

Postby Levman74 » Mar 09 2011, 8:20am

While the belt is off, you can check by hand and see if there is any drag or unusual feel from the AC pulley, same with the alternator and P/S, though it might be fine with no lateral load on it. You can also check with the standard screwdriver->ear to see if you can hear anything in a specific area near the pulleys. Be careful when getting close to moving parts though...
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Re: Knocking from some pulley?

Postby bhall88 » Mar 09 2011, 11:15am

One thing ive learned that REALLY helps finding out if bearing are worn even if the pulley seems to be moving freely is a medical stethasope. You know, the ones the doctors use to check your heart beat. It really amplifies any sound or grind to help you resolve any issues. It also comes in handy with anything unusual within the motor to find out just exactly where the noise is coming from
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Re: Knocking from some pulley?

Postby redsilverw/t05 » Feb 26 2012, 6:03pm

I have a similar issue that i have been dealing with since i bought the truck. i noticed my belt tentioner slapping around, and my crank pulley having a slight wobble causing the belt to chirp rhythmically .i just replaced the harmonic balancer, tentioner ,idler pulley,and belt witch helped with the chirp but the wobble is still there and i'm still concerned. Not really sure what to do next mmaby the pulley?
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