Has anyone ever removed the pipe assembly that runs through the intake manifold on the diesel engine on a D47U?  I need to perform a weld repair and it would be ideal if the tube was not in there.  I couldnt tell if it was pressed in or brazed in there.  Just to clarify the tube I need to remove is the tube that contains the pony motor exhaust.  See attached pic.    

I've fiddled around with a few of these lately (though haven't actually removed an inner pipe). I think if you clean up the end behind where the upright section of pony exhaust bolts, you'll find one or two retainers. These are called "ring 5f6994" in your part diagram.

My thought is that with these out, you'll be able to persuade the tube to come out backwards (toward the pony motor) without breaking the brazed on copper seal at that end.

Some of mine are loose at that end, others have sealer that might make it hard to get out.

Paul.

check the condition of that pipe. you will dust the motor and have hard starting if it is religious or cracked.

keep a tin or exhaust flap on the pilot exhaust. to keep moisture a debris out and thus pro long it life

These are the retainers in the end of the pipe. Parts manual says there are two, but I'm sure I've seen intakes that only have one.
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Paul.