Welding on oil pan while on car

Finally found that my oil leak (replaced the drain plug gasket and oil 5 times) problem is a hairline crack in the oil pan immediately adjacent to
the drain plug. The plug threads into a thickened (re-enforced) area of the pan and immediately at the edge of this thickened area starts a hairline crack that radiates outward for about 3/8 th of an inch. It is possible that the manufacturer welded this thickened area into the pan and the weld junction is either failing are developing a stress crack.
I propose to clean the area with a wire wheel and then hit it with the wire feed welder. Ground strap will be within a few inches, however I will disconnect the battery just in case. Wife will stand by with a huge fire extinguisher. Car is up on a hoist.
Removing the pan is the other alternative, but lots of exhaust pipe and cross bracing in the way. Probably about 2 hours work.
All comments, suggestions, warnings appreciated.
Ivan Vegvary
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Ivan Vegvary wrote:

My suggestion is simple. Go to the dealer, buy new oil pan & gasket, and GET BUSY.
Chances are if you weld it, you'll munge the threads and the plug won't seal. That's my best guess, anyway.
Grant
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Grant Erwin wrote:

This would be my preferred method unless I were exceedingly cash poor at that moment, or it were a vintage car with unobtainable parts.
2nd choice would be to drop the pan, dip it or have it dipped, clean the hell out of it, then weld it up (and maybe fix the design flaw that led to the stress crack in the first place).
3rd choice, after reading the responses here, would be to try the bonding trick per Maxwell. Good epoxy and clean metal can make some amazing bonds. But I'd always worry about the whole shebang dropping off on a hot day on the interstate, leaving my fellow travelers amused and me stranded.
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Tim Wescott
Wescott Design Services
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Had a good friend who wanted to change the oil pump, but didn't want the exercise of dropping the pan. He knew where the pump was, cut a hole in the pan, removed and replaced pump and pickup, welded the pan back together. I don't know what he did about getting the pan gasket too hot.
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I have in fact done this repair to a few cars over the years, and done so two different ways.
My preferred method is to fabricate a doubler that includes a new drain plug, and bond it over the leaking area leaving a wide margin everywhere possible to support the bond. Yes, it has to be extremely clean, and grease free. But it has always served me well.
The second is welding. But the only time I remember welding and oil pan "on" the vehicle, after just a few seconds of welding, I got an extremely hard POP from the combustion gasses on the inside. It bloated the metal pan, and could have been very dangerous. I don't recommend it, and would never try it again myself.
The third would be removal, and repair or replace as desired.
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"Maxwell" wrote: (clip) after just a few seconds of welding, I got an extremely hard

^^^^^^^^^^^^^^^^^^^ I know of a welding shop that welds gas tanks after running the exhaust from a small engine into the tank for an hour or so. Another idea might be to shove in several handfulls of dry ice. The CO2 will force virtually all the air out. CO2 is heavier than air, so if any air remains, it would not be at the bottom.
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I have heard that, but never had any first had experience with anyone that actually did. I would be afraid of it. I would hate to find out the hard way, that it was just a legend. I have welded gas and diesel tanks, but only after flushing them with water, then filling them completely with water, leaving a bubble only where I wanted to weld. Even at that, I have had them huff a bit.
Have you had the opportunity to witness the exhaust purge technique first hand Leo?
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"Maxwell" wrote: (clip) then filling them completely with water,

^^^^^^^^^^^^^^^^^^^^^^ I once tried gas welding some cracks around the petcock on the bottom of a Harley tank. I filled it with water, and propped it up on my bench, bottom side up. It blew. The gas cap came off, and water shot out the neck, drenching me and everything around. I figured out afterwards what had happened: water dripped put the vent hole in the gas cap, so the water level dropped slowly. Some gasoline floated on top of the water, and then ignited. ^^^^^^^^^^^^^^^^^^^^^

^^^^^^^^^^^^^^^^^^^^^ No. I was told by someone who seemed to know what he was talking about. Still, only hearsay.
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I am not recommending the procedure but we used to torch braze Harley and Indian (pre 1958) tanks by draining, blowing out with the air blow gun, clamping a mounting ear in the vice, and sticking the lit torch into the cap opening. You would get a small explosion but the small tank was plenty strong enough to withstand it. I have successfully soldered an empty auto gas tank with a 300W American Beauty iron but have never gotten near one with a torch. The accepted method of purging them used to be with a steam cleaner.
Don Young
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While not pertinent to what I am doing, standard procedure for pulling service stations out of the ground is to place enough dry ice on the bottom to displace all the combustibles. Takes several hours for the ice to release the gasses. Proof is by testing for hydrocarbons at the top opening. Until tested clear, you are not allowed to put a chain around the tank or make contact with anything made of steel (spark avoidance). After tank is cleared you can start dismantling the attached piping and pull the tank. Have done many, many of these in the past.
Ivan Vegvary
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Hum. Maybe you could just fill it up with Argon (heaver than air) (or 75/25) and get the same effect??? I'd trust a hose from an Argon tank to correctly remove the O2 from the tank before I'd try a stunt like dry ice or engine exhaust. Shit, a 2 stroke mixes the combustible fuel with the incoming air and pumps some of it out the exhaust on every cycle. Fill your gas tank with the exhaust from a 2 stroke and you would be asking for trouble when you started to weld. I wouldn't try anything like that without the correct knowledge of all the chemistry and risks and the correct tools like maybe an O2 meter at hand to verify what was in the tank.
Checking a page on the specific gravity of gases, I see some nice gases like Butane, Propane, ozone and nitrous oxide are all heaver than Argon and CO2. Yeah, that would be nice. Push out the O2 but leave the tank full of butane, propane, ozone and nitrous oxide (close cousin to nitro in chemical make up). I don't know if O2 in those forms can help the butane burn under heat, but I wouldn't be the one to bet my life it couldn't.
Personally, I wouldn't go anywhere near a welding job and tanks of highly combustible material. :) I'll let the "real" welders do that crap.
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"Curt Welch" wrote: (clip) I'd trust a hose from an Argon tank to

^^^^^^^^^^^^^^^^^^^^^ "Stunt?" CO2 gas is what is produced when dry ice sublimates. It is just as non-combustible as your argon. And I never said anything about using a 2-stroke engine. Did you throw that in just so you could argue?
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Yeah, I love to argue. (debate ideas really).
No, the other poster talked about the idea of venting the tank with the exhaust of a "small engine" (if I remember the wording correctly). I was thinking and commenting about the potential risks if that "small engine" was a 2 stroke instead of a 4 stroke. That comment had nothing to do with your CO2 suggestion.
The problem I would see with using dry ice is not that CO2 is better or worse than Argon, but that you would have a very hard time knowing how much C02 you had generated by using "a few handfuls" of dry ice and have a hard time knowing if the CO2 had evenly displaced all the O2 or if it had just mixed with the O2 leaving a lot of the O2 in the tank. With a welding tank of Argon or CO2, you could calculate how much gas you had pushed through the tank by the flow rates and you could keep it flowing at a low rate to make it slowly displace the O2 in a "plug flow" type of mix instead of the case where the two gases would mix and dilute each other and push a lot of the CO2 out with the O2 leaving a lot of O2 still in the tank.
There was an interesting article in the AWS welding Journal an issue or two back (May 08 actually) about the problems of purging a welding piece with inert gas. They had lots of good ideas about the things you have to do to make sure the inert gas had correctly pushed out all the reactive gases. They suggested for example to use a dew point meter instead of an oxygen meter because many o2 meters weren't sensitive enough to detect small amount of oxygen (they were built for safety checks for humans to breath not for the small amounts that could mess up a weld - and probably the small amounts to create an explosion I would guess). There was also the problem of bubbles of O2 being stuck in high spots to look out for. And the general issue of plug vs mixing flows that would require you to pump large amounts of gas through before the O2 level became low enough.
The complexity of doing purging correctly to back your weld with inert gas made me realize the complexity you can face if trying to remove the O2 to keep it from exploding as well.
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"Curt Welch" wrote:

Actually, no, it is very easy to know how much CO2 you would have, if you take a few seconds and look at the numbers.
The volume of gas released (at room temp and pressures) from one cubic centimeter of dry ice is about 0.83 liter (about a fifth of a gallon). If you assume that a handful of dry ice is about the volume of a golf ball (a golf ball being about 30 cubic centimeters), and that "a few handfulls" is three golf ball size chunks of dry ice, then you are looking at the amount of CO2 liberated being about 74 liters, or about 20 gallons.
As for the mixing of the gasses, dry ice sublimates slowly enough that if you leave the tank undisturbed with a small orifice for O2 to leave (to minimize drafts), you can reasonably assume that a sufficient amount of 02 has been displaced.
You can give yourself an additional safety factor if you wish; dry ice is cheap and readily available enough.
Jon
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"Jon Danniken" wrote: The volume of gas released (at room temp and pressures) from one cubic

^^^^^^^^^^^^^^^^^^^ Actually, from my drinking experience, I believe a "fifth" equals 750 cc.
As far as displacing ALL the oxygen is concerned--you don't have to. You need to displace most of it, so the remaining content of the tank is outside the ignition limits. AMHIKT (Ask me how I know this.) Okay, I'll tell you. When I ws a grad student at Cal, I worked on a project for the Air Force in which we studied what happens inside a fuel tank when an ignition source (such as a tracer bullet) goes into a tank. The object was to fill the vapor space in aircraft tanks with a non-combustible mix. We used spark plugs in most of our tests, and actually fired bullets in many of the tests.
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wrote:

UH, Curt, nitrous oxide is a catalyst that aids in combustion. Ask any hot rodder about "nitrous" and their eyes glaze over as they tell you all about their set up.
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It only takes a few hours to learn how to light a torch or to strike an arc and run a bead. It takes the rest of your life to learn WHEN to do these things.
The road to becoming a 'real' welder is filled with customers who want you to do a quick and dirty (cheap) repair using dangerous procedures which they claim some 'good old' welders do all the time. These customers always claim to be knowledgeable and experienced themselves, but always want you to be the one to do the job and to accept the risk (and liability) and to do these dangerous jobs for very little cost.
The OP of this thread seems to be willing to settle for a poor quality weld (that will be severely contaminated by oil) in order to 'save' a couple of hours of mechanical work to remove the pan, and clean and weld it properly. The oil contaminated weld will probably fail and may cause further (possibly severe) damage. Any 'real' welder that attempted this job will of course be blamed for any failure or further damage or accident.
He also proposes to do this 'welding work on a closed container that has held combustible material', in an overhead position, on a hoist, inside a (probably combustible) building, which probably contains other combustible products, and without draining and removing the fuel tank from the vehicle. He is also proposing to expose his probably untrained wife who will probably not be wearing proper personal protective equipment suitable for fighting fire in an enclosed space.
One should always think about how their actions will appear in the accident report and on the evening news.
If the vehicle is not worth a proper repair then any of the sealers or epoxy products made for sealing gas tanks are a better alternative for 'a quick and dirty' repair.
Fire or explosion is a serious risk every time we do any welding, and safety must be the first and most important consideration anytime we undertake any welding job.
Good luck, YMMV
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Fine words of wisdom.
happy 4th!
Tom
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Sounds like a fatigue crack near the weld area. I prefer to braze this type of problem where you have sheet metal and cracks but a good weld is acceptable. Biggest problem is that no matter what you do, the heat from the weld will liquify the oil and let it drain down into the weld area. Yields crappy welds, not to mention the fun of hydrocarbons on red hot metal.
You may get by with the wire feed on the car but a permanent fix involves pulling the pan. :(
Ivan Vegvary wrote:

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wrote:

This might sound crazy but why not try to soft solder the crack with a big electric soldering iron ? It should be strong enough to seal the crack and doesn't involve a temperature that can ignite anything.
I soft solder spouts on tins full of spray paint and have never had a problem.
--
Steven

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