View Full Version : Welding exhaust crack while motor running??
RoadWarrior222
01-23-2013, 12:15 PM
Hey folks,
So, I've got a header (front of head exhaust ports) on my Escort, that has an O2 sensor boss between the secondaries, that's cracked out on one side, and is blowing. I initially damaged it when I was "massaging" it to fit this application. I touched it up with ancient rods on hand with an ancient buzz box arc welder and non-existant welding skillz... which lasted a couple of months until now. Anyway, at that time I was having trouble getting good penetration, and keeping heat in the job, and the header was off the car. It was about 50F outside then. It's 40 degrees colder now, figure I'd have even more trouble keeping heat in it and getting good penetration, with the temperature, unless maybe, I did it with the motor running????
So what do ya think of that, do you think exhaust gases might be good shielding? Too much moisture will screw it up? It will blow steel bubbles and splatter me in the eyes? I'll fry the electronics in the car??
The alternative might be slapping some high temperature putty on it and waiting until spring, 'coz I don't wanna fug around in this cold removing it.
Thoughts?
RW222
Rrider
01-23-2013, 12:55 PM
Try it, sounds like it would work. Or turn it off just prior to running your bead. You will still have your heat and shield "gas" in there.
turbovanmanČ
01-23-2013, 01:55 PM
You will never weld that thin metal with an arc welder, borrow a mig or give a muffler shop a case of beer to do it.
RoadWarrior222
01-23-2013, 02:01 PM
Complain about penetration problems, Simon says "You'll never weld stuff that thin" .. buhuhahahaaaa
Yeah well, it's not cheapy exhaust pipe tubing, it's at least twice as thick, and the O2 boss is a solid chunk of metal, like it was a quarter inch walled pipe, but was probably machined out of billet.
turbovanmanČ
01-23-2013, 02:11 PM
Factory tube headers are thin wall, so yeah, an arc welder will just blow holes in it. If its a cast manifold, give it a try.
wallace
01-23-2013, 02:25 PM
I was going to post something witty but I couldn't come up with anything that I thought was good. I think you'll need to pull it off to fix it. You may want to try brazing it instead of welding if all you have is an arc welder. good luck, it is friggin' cold here so can only imagine how it is there.
Force Fed Mopar
01-23-2013, 02:29 PM
MIG weld it.
BadAssPerformance
01-23-2013, 02:34 PM
I touched it up with ancient rods on hand with an ancient buzz box arc welder and non-existant welding skillz... which lasted a couple of months until now
...so to challenge said skillz it would be best to do it sub 0°C with the motor running standing on one leg? ;)
So what do ya think of that, do you think exhaust gases might be good shielding?
Not sure if exhaust makes a good shield gas? Why do you need shield gas with arc welding? whether shielding or not if is running and gas coming out what you are trying to weld, the weld will splatter
---------- Post added at 12:34 PM ---------- Previous post was at 12:33 PM ----------
I was going to post something witty but I couldn't come up with anything that I thought was good. I think you'll need to pull it off to fix it. You may want to try brazing it instead of welding if all you have is an arc welder. good luck, it is friggin' cold here so can only imagine how it is there.
Torch braze not a bad idea, but might not last too long
85boostbox
01-23-2013, 02:42 PM
Simon is right. The problem is is that you have the amps (heat) so low that you can't get good penetration. But you have to keep them low to not blow holes in it. I agree with everyone else. Your gonna have to MIG or TIG it.
And what kind of rod were you using? 6010, 7018, or 11018? If you were going to try and arc it again I would personally use 6010. Takes less heat to get it to start. And also as stated you don't need a shield gas for arc welding. One other thing you could do if you try to arc weld is take a propane torch and heat it up that way. But as stated I doubt it will work. But just a couple ideas for you.
Rrider
01-23-2013, 02:49 PM
Just do what you did last time to buy a few months.
RoadWarrior222
01-23-2013, 04:15 PM
...so to challenge said skillz it would be best to do it sub 0°C with the motor running standing on one leg? ;) ... Holding the electrode clamp in my mouth, in hour 23 of an all day gameboy tetris marathon, yes :D
Actually it looks like it could be "easier" in some respects, because the loose header was a bugger to position and hold down, and I was crouched over it with my hand wobbling so much I had to cut the rods to half length... having it solidly nailed to something with a nice rad support to lean on seems like an improvement.
Not sure if exhaust makes a good shield gas? Why do you need shield gas with arc welding? whether shielding or not if is running and gas coming out what you are trying to weld, the weld will splatter
Well I'll let you into a secret, arc uses shield gas, it just usually comes from the "flux". If my flux is fluxed up from getting stale, or there's a bit of wind and it's getting blown off, I might do better with some other non-oxygen containing gas.... I might see how it goes, might get most of the crack done before it gets restricted enough to spatter bad, then can turn off and finish.
85bb, forgotten what rod I have, but it's some ancient 3/32 Fleetweld stuff that needs my current maxed and a lot of tapping/heat to get going. Shouldn't I buy 6011 though for an AC box? Figure I'd try and dig in toward the boss with it to tie it into that (Which is what the welds are cracking off from) and then fill towards the pipe?
Though I had so much trouble with that rod before, I'm thinking that I may as well try the classic shellac coated wire coathanger instead :D
They used to do damn well everything with arc welders, so I'm skeptical about "can't" do that with an arc welder, figure that "You need a lot of practice to do that with an arc welder" is meant.
If you can actually get to the place you need to weld, run the car for awhile to essentially preheat it and give it a go!
If you're worried that it'll cool off too fast, you could try it running, but I doubt you'd be able to "close the wound" due to escaping gases... in which case, shut it off for the last bit.
That all said, I'll have to agree that TIG or MIG would be a better choice...
Mike
bakes
01-23-2013, 04:54 PM
You realy realy want to blow all your modules or lifting your battery out of it's tray welding while running !!!! Always disconnect your ecu's and batteries
RoadWarrior222
01-23-2013, 05:02 PM
Right, so that actually can happen, it's not paranoia?
thelostartof
01-23-2013, 05:17 PM
You could always get a small torch and just heat up that area before welding it. Last time I checked you can get anything that puts out a flame for sub $40 to get enough heat into the pipe to help weld.
Or get engine nice and hot and then turn off and clean the area the best you can while hot and weld.
I had someone clean the metal really good before driving over the 15 min to my house so as they pulled up and shut off the engine I gave it a quick cleaning and rewelded their WG flange into cast manifold as the previous two tight welds with smr had cracked. A little over year since then and those mig welds have still held up.
While it can fry stuff myself I have yet to see that happen as I have welded on a ton of cars with the batt still hooked up. Most exhaust shops will do the same. As long as the ground clamp is near where you are welding it should be fine. But it is always better to be safe if you can.
85boostbox
01-23-2013, 08:08 PM
... Holding the electrode clamp in my mouth, in hour 23 of an all day gameboy tetris marathon, yes :D
Actually it looks like it could be "easier" in some respects, because the loose header was a bugger to position and hold down, and I was crouched over it with my hand wobbling so much I had to cut the rods to half length... having it solidly nailed to something with a nice rad support to lean on seems like an improvement.
Well I'll let you into a secret, arc uses shield gas, it just usually comes from the "flux". If my flux is fluxed up from getting stale, or there's a bit of wind and it's getting blown off, I might do better with some other non-oxygen containing gas.... I might see how it goes, might get most of the crack done before it gets restricted enough to spatter bad, then can turn off and finish.
85bb, forgotten what rod I have, but it's some ancient 3/32 Fleetweld stuff that needs my current maxed and a lot of tapping/heat to get going. Shouldn't I buy 6011 though for an AC box? Figure I'd try and dig in toward the boss with it to tie it into that (Which is what the welds are cracking off from) and then fill towards the pipe?
Though I had so much trouble with that rod before, I'm thinking that I may as well try the classic shellac coated wire coathanger instead :D
They used to do damn well everything with arc welders, so I'm skeptical about "can't" do that with an arc welder, figure that "You need a lot of practice to do that with an arc welder" is meant.
Ah didnt realize you had a AC box. Then yes you need 6011. Arc welding is not meant to hold and fill. You have to weave. And yes you would be correct in the matter that start your bead on the bung and drag the weld over to the pipe. Try to keep as much heat off that thin pipe. And one other thing. When you arc weld you always weld going upward. Not down. So if your going down that is why your not having success.
shayne
01-23-2013, 10:56 PM
use 6013 rod, its idiot proof, but honestly repairing an exhaust manifold with an arc welder is a fast track to blowing holes in it. and if you stray arc the thin tube you will have cracking not long after. find a mig, or use an oxy fuel welding set. exhaust gas is not sheilding gas, there is water vapour in exhaust and that alone will put you waaay beyond the practical limits of diffusible hydrogen in the weld.
but then what do i know....
BadAssPerformance
01-23-2013, 11:02 PM
Well I'll let you into a secret, arc uses shield gas, it just usually comes from the "flux". If my flux is fluxed up from getting stale, or there's a bit of wind and it's getting blown off, I might do better with some other non-oxygen containing gas....
Yeah, I meant arc doesn't need shield gas cuz it has flux... does CO make good shield gas?
I agree with Rrider, just do whatever you did before if that will buy till spring, eh?
johnl
01-23-2013, 11:18 PM
Nothin to add but yeah, clean area to be welded, run it till good and warm, re-clean, do as before. Good luck with it.
bakes
01-24-2013, 01:02 AM
Right, so that actually can happen, it's not paranoia?
I have seen both happen one cost $3000 in modules and one blew the battery up and bent the hood both happened in a body shop
shackwrrr
01-24-2013, 01:21 AM
I work at an exhaust shop and we have never seen a fried module from welding on a car. If you ground it right there are no issues. I will say that I have seen cars with bad ECU's from an exhaust shop using the O2 sensor as a ground clamp location, but where I work we are smart enough not to do that. Also we have tried welding with the car running but if you are trying to close a hole it starts making molten metal bubbles and you end up with a pile of permeable slag that is impossible to seal.
black86glhs
01-24-2013, 02:14 AM
2 words....... tig glue.
moparman76_69
01-25-2013, 04:26 PM
stop being a cheapass, get some loonies and some toonies and a few of those funny monopoly bills and pay someone to do it right.
RoadWarrior222
01-25-2013, 04:47 PM
I've played that game of roulette before... it tends to make me determined to do it myself, even if the tools to do so cost more than paying a random wrench monkey to screw it up.
---------- Post added at 03:47 PM ---------- Previous post was at 03:39 PM ----------
I'm probably not gonna try it with the motor running, can't see an angle where my knuckles won't be brushing plug wires. Another daft question though, if I screw a spark plug or dead O2 sensor in the bung hole, do you think I'll weld it in, if I connect the ground clip to it... just there's not a whole lot to grab onto on the header, can't grab the flange now, it's against the motor, had to use short studs to get fully threaded ones, (Flange slightly thinner than blank part on reg studs) so there's not a lot sticking out there. The further away I go, the more chance of the current going somewhere it shouldn't. So best place to ground seems the O2 boss itself, so could screw something in to get a nut to hold onto, but haven't got any M18x1.5 regular bolts.
3.0 van gogh
01-25-2013, 09:18 PM
yeah slime up an old spark plug with some grease or anti seize. Find a flux core mig machine either at harbor freight or a pawn shop. (they done cost too much) practice on the same thickness metal til you get the heat right. A little preheat wouldn't hurt (run the engine). the good thing about the flux core mig is that it doesn't have a shielding cup to get in the way and is not affected by wind and it doesn't mind a bit of dirt/grease/rust. Now, stitch the crack up. (short weld "bursts"). You will find that you can get into some fairly cramped spaces with the flux core mig gun because of the lack of the gas cup. I weld up exhaust all the time AND actually fill up holes with the flux core but I have too much experience at welding. the short bursts prevent the "weld through" or the "hole through" . remember to clean out the thread holes of the anti seize or grease with some brake clean.
moparman76_69
01-25-2013, 09:32 PM
Is it cast iron? If so you need a high nickel rod, preheat, and slow cool.
Force Fed Mopar
01-25-2013, 09:45 PM
I believe he mentioned in another thread that it is a factory 1st Gen Escort GT header modded to fit his 2nd Gen. If so, it should be mild steel I think.
RoadWarrior222
01-25-2013, 10:34 PM
Yah, good memory, should be mild steel, can't tell what that boss is though, since it was all lightly scaled from age, so can't tell from finish if it was machined from bar or cast and machined. Think I was seeing forked sparks when I was trying to clean it up with the grinder last time, but that could have been off the previous weld rather than the boss itself.
Dunno if a MIG purchase is doable right now, well fairly certain it isn't for a month, but I do have a lot of bodywork to do...
Force Fed Mopar
01-25-2013, 10:49 PM
It will all be steel, they didn't mix and match cast and steel.
moparman76_69
01-25-2013, 11:07 PM
FWIW I've brazed exhaust manifolds several times and never had an issue. They were all cast though.
RoadWarrior222
01-25-2013, 11:11 PM
Yeah, probably not, though it does make me wonder why it blows loud when I first start it and "seals up" as it gets hot, that's why I missed the crack at first glance a week back, looked when it was hot.
---------- Post added at 10:11 PM ---------- Previous post was at 10:08 PM ----------
BTW what's surprising me, is that this header, with a coat of "ceramic" rattlecan exhaust paint on, seems to be running cooler externally than the cast mani did with a heatshield over it. At least it's not trying to melt the cheapy wiring loom I tried to protect plug wires with, which the cast mani did.
black86glhs
01-26-2013, 02:59 AM
Cast iron is a heat sink so that is probably why it did that. That is why radiators were made from it(house ones).
wallace
01-27-2013, 11:01 AM
FWIW I've brazed exhaust manifolds several times and never had an issue. They were all cast though.
I've had good results with brazing thin material for exhaust. I had a 400cc 2 stroke dirt bike back in the day and the expansion chamber cracked all over. I brazed it up and when I finally got all of the cracks done I think there was more braze than metal but I had no issues with it and that bike was one "buzzy" machine everything on it had to be loctited.
RoadWarrior222
01-27-2013, 06:02 PM
Hmmmkay, well I've wimped out for now...
Half my problem with this car is I only get to attack it an hour or two at a time. I thought I was gonna get all day on it, but had to wait around for a phone call this morning. Then by the time I could get out of the house, it didn't leave much time for finding supplies... well I thought 3/32 rods are straining my welder to the limit, so was looking for smaller, but could only find 5/64 and 1/16 in big packs, and 6013 instead of 6011, was one place I remember having 5 or 10 rod "try it and see" packs, which I thought was what I was gonna do, but of course they don't have them now... having a tight cash period again, or I might have just bought the 5lbs.
Which might be just as well, either the crack spread since I last looked or I didn't see it had gone right round last time. And there would have been no doing it in situ anyway.
Anyway, came home with a pack of HiTempSteel stuff, which seems the same as ThermoSteel, and glooped that all round and crossed my fingers.... Few people online say it's held on cast manis for months/years. But, I am not hoping too much, think it needs more mechanical strength for where it is. Stuff seems like fancy muffler cement.
Well after getting under the front of the car to glob it well round underneath, I did a :banghead:, coz it might not have been my weld that gave first... Saw that the mounting bracket at the end of the header broke off, so it's been getting mechanical stresses it shouldn't have. Well/so it's gonna have to come off and get seen to properly, I might put extra straps between the secondaries while I'm at it, try to stop them moving much in relation to each other.
You might be wondering why I'm stalling, well, a lot has to come out, to get the header out.
I'm wondering what's going wrong though, I broke that same bracket on the last stock downpipe and the converter (In the DP) started to get a stress crack. I checked the engine mounts when I put this in and they're all lined up correctly and they're newer than the car, maybe 8-10 years old, not cracked up compressed stock rubber anyway, but seemed in decent shape. There's a decent amount of material in them too, same "bulk" as the TM ones by eyeball. Get enough friggin' vibration too, so they have to be pretty firm. Have to go looking at the good mazda mounts I guess, or immobilise the sucker with a bobble strut or something. (I swear I manage to break/stress parts nobody else does)
85boostbox
01-27-2013, 06:05 PM
No my bracket on my exhaust has done the same thing on my 93. I am thinking of installing a longer exhaust pipe.
BadAssPerformance
01-27-2013, 11:05 PM
crappy design, seen/heard many cracked
RoadWarrior222
01-27-2013, 11:32 PM
Hmmm, got a feeling it's the mazda platform with ford motor cobbled in that must be the engineering disconnect, the mazda motor seems to offset the DP. Guess I'll have to lie there and stare at it for a bit. (i.e. construct 3d model of problem in head and "software" test some solutions, before rejecting all of them as complex and/or expensive and fixing it with duct tape.)
So let the goop set up as directed, and then drove it around gently this evening, sounds a lot quieter, not sure I got 100% of the crack, but didn't wanna stab the pedal and find out, when I thought it might blow it off. After it's done a couple of highway burns, I'll check it again. Think I can "touch it up" still have a small blob left.
I am having a bit of a laugh looking round some welding websites. One guy is saying, "don't learn arc on anything smaller than a 1/8 rod" another is saying "stay below 3/32 rods until you get the hang of it", then there's the welder buying guide, which basically says, "Don't bother with X when Y is just $100 more"... up the entire range...so I guess I'm looking for a 3/4 ton truck to pull a 10kW diesel welder/generator.
3.0 van gogh
01-28-2013, 02:03 AM
well, I guess if I had your dilemma I would choose the 6011 rod. This is what I like to call the "junk yard rod." It is somewhat easier to use for the beginner and it doesn't mind a bit of rust/dirt. Ive welded in floor pan patches with the 6011. The 3/32 rod size should be perfect although don't expect to make a "pretty" weld with it. The 6013 rod is just a bit harder to use and it doesn't like dirt as much. Mostly it is used for sheet metal and in the right hands, is a great rod. Like I said earlier, if you are worried about burn through, just make short lengths of weld, this prevents the metal from getting too hot. Yes, have the amps cranked up a bit but don't try to make the entire weld in one shot. Arc welding on thin metal can be done but you will burn through before you know it if not careful. Another option if you do remove the header could be 7014 rod. It is a low penetration rod/high build rod but it doesn't like to be welded in vertical or horizontal positions. Makes a pretty weld and is very easy to use.
---------- Post added 01-28-2013 at 12:03 AM ---------- Previous post was 01-27-2013 at 11:59 PM ----------
109.99 Harbor freight flux core wire feed welder
RoadWarrior222
01-28-2013, 07:24 AM
Don't have a HF in range, cheapest around here is about $200
I'm not actually sure that most MIG guns aren't gonna be too fat, I've got about 3/4" between the 2 secondary pipes.
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