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knocking/rattle from alt housing, new alt didnt fix, have video

Hello,

i recently replaced my alternator due to a knocking/rattling sound coming from the housing. The sound did not go away. I took a few videos of the sound with and without the fan belt attached.

A little background on the knocking sound. When i took the alternator out over the weekend I found a decent sized crack in the alternator housing. I had it welded up by what i believe to be a competent magnesium welder. You can see pictures of the before cracks here. went to replace alternator and housing is cracked

Unfortunately i didnt take an after picture before i put it back in.

1st is just checking fan belt tension. Is this about right? 20120618_185902.mp4 - YouTube

2nd gets you a nice listen in on the rattling/knocking sound with the fan belt attached 20120618 190004 - YouTube

3rd is with the fan belt disconnected. Sound is lower but i can definitely still hear the rattle. 20120618 192112 - YouTube

any help diagnosing the sound is appreciated. thanks
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Old 06-19-2012, 08:47 AM
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a knock with no belt kinda makes you think it's internal, doesn't it?
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Old 06-19-2012, 09:26 AM
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The distributor maybe ?
Also listen to the chain housings, maybe a tensioner starting to fail ie; not holding constant presure on the chain.
Dosent sound like much to worry about on the video, but i understand your concerns, do some listening with a long screwdriver against the cases and your ear, be carefull, and dont wear a tie while doing it!
Hope this helps.
Anthony.
Old 06-19-2012, 09:33 AM
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loose crank gears, worn intermediate aluminum gear backlash, distributor worn out, tensioners failing, broken chain ramp, piston slap, wrist pin bushings worn, rod bearing, loose crank pulley, valve tick.....
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Old 06-19-2012, 10:09 AM
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Is that fan belt tension proper? I thought maybe it was one shim too tight.

And John, yikes! I'm due for a tuneup and valve adjustment. We'll see how it sounds after that.
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Old 06-19-2012, 10:24 AM
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Quote:
Originally Posted by john walker's workshop View Post
loose crank gears, worn intermediate aluminum gear backlash, distributor worn out, tensioners failing, broken chain ramp, piston slap, wrist pin bushings worn, rod bearing, loose crank pulley, valve tick.....
Nothing serious then John!
Realy hope you get to the bottom of it.
A...
Old 06-19-2012, 10:25 AM
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Can anyone confirm if my belt tension is correct (see first video)

thanks!
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Old 06-19-2012, 06:54 PM
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Tension looks good to me but difficult to tell how hard you are pressing, should take a fairly firm press for that much movement imo. Re the noise, lets add exhaust leak or broken head stud to the list just to be sure you never have a restful nights sleep ever again. Probably a wild valve gap.
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Old 06-19-2012, 10:56 PM
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Belt might be one shim too tight, if it's a new belt it'll stretch just a bit and you'll be fine. Or, add another shim inside and see if it's too loose.
Old 06-20-2012, 09:05 AM
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Was the noise present before you repaired the fan housing? If not, then I suspect there is interference between the crank pulley and the housing. What else could it be if the fan and alternator are not turning? If the noise was present before your repair and you attributed it to the cracked housing, then the problem is elsewhere in the engine. A simple diagnostic would be to remove the fan housing and alternator and run the engine for a short period without them installed and see if the noise persists. Good luck!
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Old 06-20-2012, 10:06 AM
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The noise was present before the alt was replaced and the housing repaired.

One more important note. On a cold start there is no noise @ that 1100rpm for the first 45 seconds or so. Once the car settles into it its 900rpm idle (car has a chip) that when the noise appears. I do find myself stalling out occasionally from stop to start in first gear. But the car idles fine at 900rpm so i don't think its a vacuum issue.
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Old 06-21-2012, 10:13 PM
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