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Old 08-15-2012, 02:44 PM   #1
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Beware Cummins 5.9 pencil zinc drip

As most who have a Cummins 6b motor know, there is an pencil zinc in the heat exchanger. It is oriented so that the zinc screws in from the bottom.

I usually use a cup or two to catch the drippings when changing this zinc, but I apparently did spill some salt water during a change out in the past.

The zinc is in close proximity to the alternator and of course some of this salt water made its way to the Positive cable running from the alternator to the house bank.

Since I don't know when I spilled, I don't know how long it took for the corrosion to cause the failure in the cable.

It is pretty interesting that the cable still was carrying around 100-150Amps just prior to failing. When it failed, it was a complete breakage of the cable at the barrel of the crimp.

I did cut back the insulation interested in seeing how far the corrosion had migrated and found it showing up 8" from the end.
The cable is 'tinned' marine wire. The crimp was well made and well sealed with heat shrink just like you want it.

Just goes to show how determined that salt water can be.

The cable was fused at the battery bank it served, but fortunately did not short out against anything when it broke. Lots of wire ties helped.

I will probably be fabricating some sort of shield to protect the alternator and its connections from any future splashing.

Also, good timing as our 8 week cruise is just finishing, so will make the permanant repair soon

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Old 08-15-2012, 06:29 PM   #2
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I always wrapped a trash bag (empty of course) over the alternator when I did that. I caught that one but then again there was likely something else I missed.

Jay Leonard
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40 Albin
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Old 08-15-2012, 07:06 PM   #3
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Now you've got me worried. I'll have to check mine.
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Old 08-15-2012, 09:31 PM   #4
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I had to do the same thing on the starters for my 6.354 Perkins. The starter and solenoid are right under a raw "saltwater" pipe inlet joint and a water outlet elbow and hose joint all serving the exhaust manifold!! Crazy!! Where do you suppose the water goes when any of the four hose clamps leak?

I actually had plastic bags over them, until I figured out how to make a durable plastic shield.

ps (A small soft plastic painters pail cut in half lengthwise and trimmed to the right size makes an excellent drip shield.)

Larry B
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Old 08-16-2012, 01:13 AM   #5
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Originally Posted by HopCar View Post
Now you've got me worried. I'll have to check mine.
Me too!
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Old 08-24-2012, 11:50 AM   #6
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I have a similar problem and use Corrosion X to prevent damage.

Still, the idea of a shield has merritt and I will follow up with the plastic painters bucket idea.

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Old 08-26-2012, 12:18 AM   #7
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I used an old kitchen cutting sheet my wife was going to chuck. It's thin and clear with a matte surface on one side. Quite flexible and tough. Can be cut with scissors and punched with a paper punch to secure with Tyraps.
Lots of materials can be adapted, even an old crummy fender that you can't quite toss but you won't use again.
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Old 08-26-2012, 08:05 AM   #8
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I put a "Pet Piddle" pad under items which might leak a bit during repairs, zincs, impellers, and so on. These pads have an absorbent mat on one side backed by a sheet of plastic, so it absorbs without splashing. Won't work for large amounts of water but fine for those jobs. For larger amounts of water I can usually fit an empty pliable yogurt, or other food container, which fits or can be cut to fit, to collect the water.
Steve W

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cummins, pencil, perkins, zinc

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