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  #1  
Old 08-19-2001, 06:06 PM
ivan
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Question help w/bearing noise on 300E passenger side

Help! Got what sounds like a bearing from either the alternator or water pump. Only does it when hot. Doesn't seem to change with engine speed . Is intermittent and seems to start when turning, backing up, or stopping (assume worn bearing is moving up or back on any of those). Lasts from 1-10 seconds. Sound like a bearing. Does seem to be coming from passenger side of engine. Have replaced the heater fan, sagging transmission mount and front flex disk (the latter 2 needed replacing anyhow).

Can't seem to isolate the noise as it stops by the time I get the hood up. Of course I've tried having the wife back up and go forward with me at the open hood but noise won't cooperate.

Assume best way to check is to pull off serpentine belt (ugh) and spin everything. Don't get any play on alternator pulley or viscous fan with belt. Alternator is putting out correct amps and volts at idle and higher RPM's per Autozone check. Water pump replaced 30K miles ago. Car has 151,000 miles.

All suggestions appreciated! Noise is driving wife and me bonkers!
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  #2  
Old 08-19-2001, 08:51 PM
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Cool

Check the serpentine belt tensioner shock, towards the top and front of the engine. Common problem for older vehicles.
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  #3  
Old 08-19-2001, 08:58 PM
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Ivan, the alternator and idler pully are on the passenger side of the engine. If you are sure of the location, it can only be one or the other of these. I would bet on the idler pulley,,
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  #4  
Old 08-19-2001, 09:21 PM
ivan
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2 good suggestions so far! Thanks, guys. To add additional information, the car is a 1989 300E. The idler pully was replaced 10K miles ago. The belt tensioner shock was noisy, but cushioned the top bolt and it isn't noisy now. In cehcking records, the water pump was replaced 65K miles ago; not 30k.

Can only agree that its the alternator. Hate to spend $200 for a rebuilt only to find out that isn't it. Any way to test if the alternator bearing is bad besides pulling off the serpentine belt and spinning it by hand for noise? Not seeing any play in the pulley with hig engine revs and the belt attached (but wouldn't expect any).

Thanks for the suggestions as always!
Ivan
Wilmington, NC
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  #5  
Old 08-20-2001, 11:30 AM
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"Can only agree that its the alternator."

It could be a slipping belt, when an electrical load switches on. Is it likely to happen when turning on the headlights?

My experience with worn alternator bearings is that you will notice shaft wobble with the belt removed, even if you don't hear bearing noise when spinning it. BEWARE of misinterpreting commutator brush noise or squeaking as coming from the bearing.

Steve
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  #6  
Old 08-20-2001, 03:15 PM
N. Gilbert
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Noisey bearing solution

Your solution is quite simple. Go to a reputable automotive tools shop and buy a bearing stethoscope. Place the sensor on the body of the suspect part and prepare to be amazed!!!
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  #7  
Old 08-21-2001, 09:44 AM
Jack
 
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Location: Sugarland, TX
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Check the fan bearing clutch bracket, and the air pump clutch. Both of them are on the right side of the engine.

jack
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  #8  
Old 08-22-2001, 01:43 PM
ivan
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Still no answer to this problem but was unsuccessful in loosening or tightening up serpentine belt. Apparently the owner before me tried to do this w/o loosening the 19 mm. tensioner bolt. After struggling and getting it loose, the 13 mm hex nut just spins.

Suspect the hex head on the threaded shaft is stripped, but before I take off the air cleaner to get the nut off and ordering another, does anyone has any experience with whether I can expect the treaded shaft to be stripped too? If so, I'm in for a much harder project.

Thanks again!
Ivan
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  #9  
Old 08-22-2001, 02:53 PM
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Ivan:

The 13mm hex nut(tensioner) is part of a threaded rod that's goes downward and into the back of the tensioner. If it's turning freely, I'd say the rod has popped out of the tensioner and conventional tightening of the serpentine belt is not possible at this point.

The serpentine belt should be snug when it's tightened and you push down on it from the top after everything has been tightened down, to include the 13mm tensioner nut(which seems to be hosed) and the 19mm tensioner locking bolt. My guess is that if you were to retighten the 19mm bolt, you'd have excess slack in the belt. What "might" help until you can repair the tensioning system, is to loosen the long bolt at the very bottom of the alternator(15mm in my case) and tug on the alternator to reacquire some degree of tension in the belt.

If you do not have one, I'd obtain a 124 CD-Rom or the M103 engine manual(hard copy and hard to find).

Your belt tensioning system is not functioning as designed and needs to be repaired.
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  #10  
Old 08-22-2001, 03:12 PM
ivan
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Thanks Mike, I'll try that tonite. In my case, I can see that the threaded rod is NOT spinning when I turn the hex nut. that makes me suspect that only the hex nut is stripped. I'm hoping that it's only the nut and not the rod threads so that I can replace the hex nut and be on my way to a proper adjustment of the belt!.
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  #11  
Old 08-23-2001, 02:51 AM
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If your threaded rod is stripped,it will probably need to be replaced. The tensioner needs to be pulled because the rod is part of an assembley that locks on the tensioner only when it is removed. I can suggest a temporary fix for this. I loosened the 13mm tensioner nut and jammed in a spacer so the tensioner adjuster would grab where the threads were not stripped. I used a quarter inch U-bolt clamp as the spacer(it looks like a mini universal muffler clamp and is typically used for the cables on garage doors). I had to grind it down with a die grinder to make it fit, but I was able to tighten the serpantine belt and it lasted 3 years before I replaced the assembly when I did the water pump.
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  #12  
Old 08-23-2001, 02:53 AM
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Also you cant replace the 13mm nut without pulling the whole tensioner assembly.
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  #13  
Old 08-23-2001, 12:17 PM
ivan
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Thanks for the hint, JDUB. I discovered last nite that I can't tighten the belt by loosening the lower alternator bolt as there is no play there. I also discovered that the 13 mm. nut is reverse threaded so I apparently have been screwing the nut off rather than down.

Will try the nut again tonite and if not, will try your fix. Will keep you posted.
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  #14  
Old 08-23-2001, 08:15 PM
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this is how we found the bearing noise on my 300SD. take a golf club or other solid metal rod. Place the handel end of the golf club(making sure no rubber grip is between the rod and the engine) and put your ear up to the other end. put the rod in differant places. You should be able to hear the engine running, and also hear any bearing noises. You can't really put it right on a pully but you can rule out other stuff. turned out to be the alternator on mine. you could here the bearing through the club even though it wasn't making noticible noise otherwise.
R
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