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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #1 (Edited)
My friends '05 OBL started having issues last week that at first he thought was the steering pump and then the alternator making noise like a bearing was bad. He finally was able to get down to my shop when he got off work, and I found that the problem actually was that the alternator tensioner bolt that threads into the alternator had broken, letting the drive belt get really loose. Thankfully I had a duplicate of that exact bolt out of my '01 legacy wagon.

However, once I got the threaded portion of the broken bolt out of the alternator, I discovered that the real problem was that the mounting pivot bolt was no longer tight, which had allowed it to vibrate for god only knows how long, wearing open the holes in the mounting bracket, as well as vibrating the tensioner bolt long enough that it finally broke.

Upon further examination, it was easy to see that the ears on the mounting bracket that the alternator bolts to are cast way too thin to withstand the bending load put on them when the through bolt is tightened - compared to the bracket on my '03, they are only maybe 1/4 as thick.

The solution for a long-term fix was to machine up an aluminium tube to surround the mounting bolt and take up all of the space between the 2 mounting ears.

Inspect yours and see if the mounting bolt can be tightened further. If it can, those ears are giving way. The fix is to put a spacer in between them.
 

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2008 Outback Wagon LL Bean Limited 2.5i
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My friends '06 OBL started having issues last week that at first he thought was the steering pump and then the alternator making noise like a bearing was bad. He finally was able to get down to my shop when he got off work, and I found that the problem actually was that the alternator tensioner bolt that threads into the alternator had broken, letting the drive belt get really loose. Thankfully I had a duplicate of that exact bolt out of my '01 legacy wagon.

However, once I got the threaded portion of the broken bolt out of the alternator, I discovered that the real problem was that the mounting pivot bolt was no longer tight, which had allowed it to vibrate for god only knows how long, wearing open the holes in the mounting bracket, as well as vibrating the tensioner bolt long enough that it finally broke.

Upon further examination, it was easy to see that the ears on the mounting bracket that the alternator bolts to are cast way too thin to withstand the bending load put on them when the through bolt is tightened - compared to the bracket on my '03, they are only maybe 1/4 as thick.

The solution for a long-term fix was to machine up an aluminium tube to surround the mounting bolt and take up all of the space between the 2 mounting ears.

Inspect yours and see if the mounting bolt can be tightened further. If it can, those ears are giving way. The fix is to put a spacer in between them.
Great information especially for high mileage Gen 3. Metal fatigue starts to come
Into play. Think of airplanes and how much vibration the outer surface and fasteners see.


What size tube did you use ?


Sent from my iPhone using Tapatalk
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #3
Machined it down from a solid 1" bar of 6061 that I had handy. If I remember correctly, I turned it to somewhere around 5/8th, then found that I had to machine a flat on one side to clear the casting in between the 2 ears, and then sand the ends at an angle to conform to the tapering thickness of the ears. If I were to do another one, I'd probably turn it to 1/2 inch diameter instead. Once custom fitted, everything tightened up nicely. He'll be here again next Tuesday for me to try to change out his front O2 sensor, so I'li double check that everything is still good.

Yea - finding the bolt broken was a real surprise, as it is something you would never expect to see!
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #4
For those who are curious about this add-in piece, here it is. As you can see, it is nothing special - you just have to make it fit in tightly between the mounting ears. As you can see, those ears are rather thin to be tightening against and expect to not flex easily.
493099
 

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05 GT wagon, 09 Spec B, 18 3.6R Outback
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Just saying, that insert/spacer looks like a deep socket. May be a 5/8 or 11/16".
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #6
HA ha! You are right! I believe that a 3/8th socket, 3/8ths drive might be long enough to span the space and clear the mounting that this one needed to have the flat machined on it to clear. You would still need to angle the ends so that they fully contact the mounting ears. The only issue might be that the rather small face area of the socket end might slowly wear into the mounting ear and cause everything to loosen up again.
 

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2005 Outback VDC limited 3.0r
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HA ha! You are right! I believe that a 3/8th socket, 3/8ths drive might be long enough to span the space and clear the mounting that this one needed to have the flat machined on it to clear. You would still need to angle the ends so that they fully contact the mounting ears. The only issue might be that the rather small face area of the socket end might slowly wear into the mounting ear and cause everything to loosen up again.
Did you coat either piece to prevent any galvanic corrosion that may occur? Or not really worried about it long term?
 

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Discussion Starter #8 (Edited)
Aluminium against aluminium is not going to corrode (6061 is a common aluminium alloy, if you weren't aware of that), so no problem there. If you used a socket, though, you would get some corrosion over time, depending on how much time it spent wet with water, but a coating of neverseize most likely would prolong that issue well beyond the life of the rest of the car. Really no more of a problem than all the other steel bolts clamping aluminium parts in the engine bay.
 
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