Author	[Modern View]
Lanse 02-28-2013 21:23:29 206.55.217.126 Report to Moderator	Goodevening everyone!! So, here's a picture that someone sent to me, part of a John Deere tractor... As you can see, its an exhaust pipe thats... cracked... If it were a standard piece of exhaust tubing, I could fix it up in no time... Just grind it out, and weld it up... But I've never seen a crack like this before... Looks brittle, almost like cast iron, but the part itself looks like standard galvanized exhaust pipe... The only thing I can think, is that it's steel, and rusted paper thin on the inside (even tho it looks good on the outside) and this is just where the internal damage is starting to show... Kinda like pinholes forming in the bottom of an old air compressor... Anyway, I just thought I'd ask here... I'd have to have the guy bring his tractor out, just to have the entire pipe shatter like glass when I tried to work on it... Any thoughts? Like I said, I've never seen anything like it, but thats not saying much :P Thanks in advance, guys... [Reply]   [No Email]
bill mart 03-01-2013 21:51:04 69.204.65.189 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   when you get into it let us know what you find. Thanks. Bill [Reply]  [No Email]
Ron-MO 03-01-2013 19:48:53 174.131.238.244 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Braze it up. Here is fix I did a couple years ago by brazing it up, and will probably outlast me. This had a very large piece busted out of a manifold, and I just cut out the bad portion and brazed in a piece of galvanized pipe. Brazed manifold pipe [Reply]  [No Email]
RodInNS 03-01-2013 18:29:58 216.118.158.123 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Replace the pipe.... A chipping hammer will knock a hole in the rest of it just about anywhere you want. You can mabey weld the crack up today but it's not going to last long. Welding on tissue paper exhaust pipe is just heartache looking for a home. Rod [Reply]  [No Email]
ss55 03-01-2013 12:10:03 173.31.19.80 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   The metal around the crack also looks very fatigued. Welding up just the crack may further weaken the surounding metal so it could soon crack in a different place. Could you add a brace or two from the flange to the pipe above the bend to carry the vibration loads and then add a patch or surface bead to seal the crack? The inside of the pipe would stay smoother and the loads on the bend would be reduced. [Reply]  [No Email]
atlarge54 03-01-2013 11:28:14 69.35.192.125 Report to Moderator	Re: Explain this crack in reply to BSpauld, 02-28-2013 21:23:29   I'd clean that up, braze a patch over it and never look back. If that exhaust gets hot enough to melt the braze the motor is likely to destroy for other reasons. [Reply]  [No Email]
jon f mn 03-01-2013 06:39:15 70.196.200.70 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   I've been asked to fix many of those, especially on snomobiles. It's from heat stress. You can just mig it but it won't last long. The pipe needs to be replaced. If you can get a patch to lay over it you will get better results, but the rest of the pipe is fatigued too. You should check the rusty area for rust through before you go to far. [Reply]  [No Email]
GordoSD 03-01-2013 05:52:03 216.106.243.55 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Compression stress cracking. Enhanced by vibration fatigue. removal of some material will releive the stress. Don't let it get in the motor. Then weld as any other mild steel. [Reply]  [No Email]
dr sportster 03-01-2013 05:26:47 68.192.200.206 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   By the time you posted the picture you could have gas welded it right in place. When I was a weldor in the USMC I chased down many exhaust horrors because nobody has money. If you make a small hole just fill it back in . Seems like alot of welding jobs are gettin' way overthunk. No one has ever successfully welded iron with Ni rod according to this site either [which just ain't true.] Its a steel exhaust pipe NOW GO FIX IT. [Reply]  [No Email]
Diydave 03-01-2013 05:20:01 96.244.162.208 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Pipe bent too cold. to fix, i'd find a size bigger elbow, and cut it into halves or quarters, weld them together, piecemeal. [Reply]  [No Email]
Hobo,NC 03-01-2013 04:57:36 71.30.104.24 Report to Moderator	Re: Explain this crack in reply to Gambles, 02-28-2013 21:23:29   Bring that cylinder up on compression stroke clean and weld... I see no need to over kill it all you are looking to do is buy a few more years of use out of it... [Reply]  [No Email]
Bret4207 03-01-2013 04:04:24 64.19.90.196 Report to Moderator	Re: Explain this crack in reply to evilboweivel, 02-28-2013 21:23:29   That's rusted like you thought. Brazing is what I'd do. [Reply]  [No Email]
Stick welding 03-01-2013 11:07:44 198.53.83.89 Report to Moderator	Re: Explain this crack in reply to Bret4207, 03-01-2013 04:04:24   Way too hot for brazing! [Reply]  [No Email]
RodInNS 03-02-2013 07:10:40 216.118.158.123 Report to Moderator	Re: Explain this crack in reply to Stick welding, 03-01-2013 11:07:44   I kinda tend to agree with you that it's too hot for brazing. Generally I wouldn't... but in this case you can see the discoloration in the bend that says the bend was a lot hotter than the rest of the pipe... which is quite natural. I would say it probably takes on a dull red that would be visible at night... which is mabey not hot enough to make brass run but it's certainly hot enough to make it soft and weak. Rod [Reply]  [No Email]
Stick welding 03-02-2013 09:56:46 96.53.210.246 Report to Moderator	Re: Explain this crack in reply to RodInNS, 03-02-2013 07:10:40   If I remember right, brazing is good up to about 800 deg's. Directly out of the exhaust port and a bend too boot, would get that pipe pretty darn hot when that engine is working. I think exhaust temps can reach 1200 and even 1600 deg's. Some exhaust throws flames and does gets glowing red when you see it at night. The discoloration could be from rain on the hot exhaust pipe. The pipe could just be worn out too. I've seen a cast iron manifold worn out from getting so hot. It was on an IH tandem with a 549 V-8 gas engine. [Reply]  [No Email]
RodInNS 03-02-2013 10:26:54 216.118.158.123 Report to Moderator	Re: Explain this crack in reply to Stick welding, 03-02-2013 09:56:46   EGT on that little thing shouldn't run much above 900 in the pipe. 900-1000 is fairly common. More discoloration in the bend is fairly common because the blast is directed at it and focused on that spot. It was always a common thing to see Ford's that were turned up... blow the top bend out of their mufflers. I've brazed diesel exhaust pipes before. Generally, if the high temp paint on the pipe hasn't been burned off the brass will be fine... but in this case... I'd say the pipe is already thin from the inside. It probably wasn't much more than 16 ga anyhow. It's just thankless trying to fix that. One thing to play with it; quite another to charge someone money for it. Rod [Reply]  [No Email]
Farmerhr 02-28-2013 23:30:47 108.224.0.124 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   That looks like a fatique failure to me. In this type of crack, there is no deformation and the crack is not perfectly straight. Besides reducing the vibration, support at the upper end will reduce the stresses. Any metal thinning will make this type of crack more likely also. Hope this helps. [Reply]  [No Email]
Stick welding 02-28-2013 21:59:12 96.53.210.246 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Probably just steel tubing. An exhaust pipe is under a lot of stress from the heating and cooling, especially real close to the manifold. I've seen cracks like that on dirt bike exhaust. Clean it good with a wire brush/sanding disc and see if you could TIG it or gas weld it. MIG might work too but you don't want to blow a big hole in it. If you can at least get a couple tacks on it, then you could make a patch to go over it to add some reinforcement. [Reply]  [No Email]
Ken-Pa 02-28-2013 21:39:31 75.179.46.144 Report to Moderator	Re: Explain this crack in reply to Lanse, 02-28-2013 21:23:29   Here"s my guess . It looks like metal stress wrinkles from bending the pipe . Could it be metal fatique plus vibration thru time causing the crack ? I"d try grinding that area bright & shiny plus cutting a V in the crack . Set up your mig welder , heat that area with your torch & then make small tack welds & finalizing it with a good solid weld . Also it may help even more to drill small holes at each end of the crack before welding so the crack won"t go any further . I had a similar situation with the rear blade for my tractor . The PO (my Uncle)had used it roughly with no care at all. HTH ! God bless , Ken [Reply]  [No Email]