My tensioner has broken for the last time

mblaney

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My tensioner has broken for the last time. The engineer who designed this to use a swagged aluminum casting to hold it together deserves a slap. There are two problems with the existing tensioner.

- The center casting (aluminum) is swaged / flared to hold the assembly together. The torsion spring is also under significant compression, all of this force working against the swage end.

- The second problem is the “bearing” is a tapered plastic part; it tends to bind and as the part wears the tensioner works out of alignment. I also found this bearing to be very stiff and hard to rotate. This prevents the tensioner from moving freely.

This is a two part process; the first fix will be temporary so I don’t waste another $100 on a POS part that will randomly fail in four months to a year and a half.

This is the broken part. The star shaped casting (on the right, surrounded by the spring) is inserting through the steel washer and swaged. This is the failure point for every tensioner that I have had. Once this fails the tensioner is puked forward into the fan, and the belt is derailed.
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My temporary fix is to remove the core of the tensioner, machine off the star shaped crimp end, and create a countersunk recess in the back.
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I purchased a longer bolt (M10 x 1.5 – 80mm long), a 3/8 fender washer and an M10 nylock nut. Before assembly I lubed it with synthetic marine grease.
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Assembling this takes a little perseverance, the tensioner spring is under torsion and compression. The nylock nut fits inside the countersunk hole. In this pic the nut is just started; it needs to be tightened to leave a little slop for the bearing, plus the bolt thread has to be exposed for assembly on the engine.
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Here is the completed assembly. I made sure there was a little axial movement (compression) by adjusting the nylock. The bolt thread protrudes the same as the original.
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Cont'd...
 

mblaney

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Here is a front view showing the original steel washer and my new fender washer. Tensioner pulley fit perfectly over this with no interference.
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That’s it for the temporary fix. The tensioner is on the truck and works extremely well; I am confident that this “temporary” solution will last longer than the original chitty design. Total cost was $6; I used my lathe to do the counter bore but this could be done with a drill bit – the center casting and the bolt do not move after assembly so the tapered bottom (from the drill bit) will not be a problem.

Thanks for looking! Part 2 coming soon... Frankenstein Tensioner.
 
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Thewespaul

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I had similar issues. Drove me crazy! I ended up drilling and tapping the acc bracket for a much larger bolt and made my own bushing. Haven’t had an issue since
 

franklin2

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I have never had that problem? Oh wait, I have v-belts. :) Besides the more driving power you have to drive a 3G alternator, I don't see any advantage to a serpentine belt system. I know driving a alternator at 130 amps can be difficult with v-belts.
 

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