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Old 06-16-2018, 08:34 PM   #1
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Onan MDJE broken exhaust nipple

The exhaust nipple on my Onan 7.5 MDJE located between the exhaust manifold and the injector elbow broke off this weekend. Does anybody on the forum have experience replacing this item and any tricks they can impart to me? Is the nipple a standard steel or black iron nipple? How would one extract the part of it that is broke off flush with the injector elbow? Thanks.


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Old 06-17-2018, 01:05 PM   #2
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There are "easy outs" to fit pipe. If the break has rust it's probably steel. You need a penetrating oil that includes a mild acid. It eats the rust in steel and cast iron making the threads looser. Heat applied to the elbow may help, but if the elbow is cast iron too much heat can crack it.
An alternate method is to insert a metal cutting blade into the fitting and cut thru the full length of the pipe fitting just to where the threads show. Then with a punch and hammer, hit the edge of the pipe on both sides of the cut, collapsing it toward the center. Work your way down the cut line and the fitting eventually becomes loose. Easier if you take the elbow off to somewhere it's easy to work on. Or once the elbow is off, take it to a machine shop.

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Old 06-17-2018, 01:34 PM   #3
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If you have to drill it completely out there are ways you can retap the hole. Commonly used in the auto field called Heli coils if you need to drill the whole plug out. As another remedy. If that is a option.
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Old 06-17-2018, 02:21 PM   #4
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Do you have a torch? If so you could melt the steel leftover shell from the threads while prying it with a screwdriver to collapse it in on itself.

Or, carefully using a jigsaw, cut the inside of pipe but don't get into the threads, do this on 2 sides, the using a hammer and cold chisel-screwdriver whack the remains inward.
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