Removing rusted in place outer exhaust metal tube from inside tube of heat exchanger of Atwood furnace

[guy_ethier]

Well, on to another headache and PIA with my 8531-IV-DCLP furnace.  Decided to remove it to try to fix it once and for all as the outer exhaust tube is rusted tighter than you know what to the inner tube coming from the heat exchanger. This tube is supposed to just slide out, but when I removed the other one from the other side of the coach, it took me a couple of weeks as well (working with Blaster and time) only to find that a build up of rust inside was the culprit.  This furnace is much harder to work on than that furnace was.

Been using PB Blaster for several days, my propane torch, several large wrenches and hammers, and a gear chain wrench all to no avail.  Is there a better way to remove this stuck on rusted in place PIA outer exhaust tube?  I even removed the heat exchanger from the furnace frame to get at it better, but it still is not budging.  

In the second picture you will see what the problem is why the furnace was not working. About 1/2 cup of rusted heat element and a rusted heat element.  Am replacing that plus getting a new electrode unit as we speak and although I can probably still put everything back together without removing the exhaust tube, it would be nice to be able to in order to check on the electrode and heat element in the future without having to rip out the furnace every time!

 

 

[Paul J A]

Soak it with a 50/50 mixture of ATF and Acetone. The BEST penetrating agent you will ever use/find.

[Benjamin]

One of the best ways to loosen that would be peening the outer tube with many small hammer blows, ideally with a heavy pipe on the inside to hit against.  That will loosen the rust and upset the metal on the outer tube to help it loosen it's grip. A ratchet strap on each tube pulling apart might help. Once loosened, hit it one way then the other to wiggle it off with the pressure applied.  If you use a torch, heating the outer tube evenly, then cooling the inner tube would be ideal.  Possibly a damp sponge could accomplish that?