Welding Water/air tight

[KS2K]

All my welding has been self taught over many years. The one problem I have not been able to over come is water tight / air tight welds without a small leak somewhere. As an example, I have recently made some serious changes in an engine oil pan for more clearence. When finished, everything looked great. Put it back on the engine and filled with oil, and a very small weep at just one spot.

My air/water tight problems are when MIG welding on thin sheet. I do the tacks every few inches, let cool, repeat this cycle. Then go back and tack in between the first tacks letting tacks cool. FInally when I an down to about 1/2" between tack, I weld in the spaces.

I would appreciate any instruction/tips on how to weld seams in thin sheet, making it water tight/air tight the first time.

Thank You
Paul

[Paul Seaman]

Paul:
I've had a similar problem on an oilpan turns out the problem was insufficient fusion to the spot welds and the oil was getting through the pan like a wick and weeps out. The last one I fixed weeped the same and an engine builder friend told me to take the Oxy fuel set and lightly butter my finished weld to close up the areas that wicked oil through. When I finished it looked like it was tig welded because the crown of the weld was washed into the weld instead of standing on top. After a little class in mig my welds are much better and now I don't seem to need to fix oilpans go figure.
I hope this helps.

[Blondie_486]

Guys,

This is the exact reason I use the magnaview lenses inside my helmet. You have to carefully watch your puddle if you watch close enough you can see the air pockets and voids. It's harder to do with MIG welding than it is TIG welding. Myself I prefer to TIG oil pans when modifying them they come out so much better.

I can understand however MIG welding them if you don't have access to a TIG welder, in which case going over them with the oxy-acetelyne torch should solve the problems. Just use a small tip (000, or 00) and heat the weld up and push the puddle along the weld. You'll see right away where the potential leaks might be as soon as you come across one while pushing the puddle along. Use something like a #4 or #5 shield or goggles so you can concentrate on watching the puddle closely when you come to a void you may have to use a little more circular motion on the torch to get it to melt togehter but I have had to do it that way on an occasion or two. A couple of times I didn't even have access to a MIG just my oxy-acetelyne rig so I welded them with a torch. Using a small enough tip, back stepping and skipping around you can successfully weld an oil pan with a torch and not warp it to smitherines.

I think one of your problems is too many tacks!!! I always use as few tacks as possible it's hard to blend in your active weld puddle to a tack weld without making a hump over the tack. Try pushing your puddle into the tack weld and ending in the tack weld then start on the other side of the tack and weld into the tack then backstep into your previous welds there is less chance of not fusing into your tack than trying to begin your puddle in a tack, there's too much material to heat up and your puddle will lay on top of the tack. Where if you end in the tack you're pushing a molten puddle into a larger mass than you've been welding.

Have any of you thought of filling the oil pans with water and static testing them before installing them on an engine? I always static test the ones I weld (fuel tanks too), no matter how perfect I think the weld might be or look. It sure beats having to drain the oil or worse if it's in the car having to remove the engine again and then pull the oil pan back off. Having to try to clean the oil off the inside so it doesn't flame up when you weld it.

Recently I had to work on an evaporator at work it wasn't a high pressure evaporator but I had to replace the insides which meant cutting the thing in half then welding the new insides in and welding the tank back together. I also extended the height of the tank upon reassembly. At any rate the boss wanted to ship it as soon as I finished my last weld, but I insisted on static testing it first so we filled it up with water. And guess what? None of my welds leaked... BUT in the process of cutting it apart I had slipped with the plas cutter and nicked the tank and it leaked there. It also saved us a lot of grief because after fixing the nick I filled it with water again and the company's engineer happened to come in about something else and saw it sitting full of water and no leaks. So when their maintainence crew installed the unit and it leaked we didn't get blamed for it because the engineer saw that it wasn't leaking before it left our shop.

I don't know about ya'll but I always paint my oil pans and don't like having to mess up the paint with a repair to a weld. Somehow they never seem to look the same after a repair job.

This sort of reminds me of an episode of "Monster Garage" when they built the trike out of the Cummins diesel out of the "Pete". The guy cut the fuel tank apart to clear the differential housing then welded it back together. When they were all done and put fuel in the tank. Guess what??? You got it!! A leak!!. I picked up the habbit of either static or hydro testing any pressure vessel or tank when I worked at the boiler shop. There's nothing worse than to put everything back together just to have to take it all back apart again because you got in a hurry and didn't test it.

Blondie

[Paul Seaman]

Blondie:
We tested with water as a static test but this engine turns 9000 rpm at the end of the straight and the windage puts some serious pressure on it much more than a static test my guess is that we are twisting the pan on the engine and developing stresses. This pan has been through a couple of blow ups and one was a schrapnel attack so this pan has been fixed multiple times and the repairs were a stop gap since a new pan is $600. However I have a new pan now but it is too tall so good and bad, good I get another chance bad is cutting a new pan in half and sectioning 2" out of it. I am sure that it won't be too bad I am better than I used to be.I'll let you know how it goes.

[KS2K]

Thanks for all the great help

I appreciate your help. Now, armed with your suggestions, I am going to weld up some sheet steel boxes, open top for practice. I did receive one piece of information today talking with a engine guy, after making mods to oil pans or other water tight enclosures, he fills them with Laquer Thinner. He claims its so thin that it will find holes that water will not find.

I am not ready to build a deep sea vehicle yet ha ha

Paul

[Paul Seaman]

Paul:
The lacquer thinner makes sense, I also found penetrating spray for testing. Let me know how your progressing. I'm not ready to build submersibles either :}
Be cool

[Blondie_486]

Paul & Pj,

It just takes some doing to get the hang of it. I had thought of lacquer thinner but at 12 bucks a gallon (and that's for the cheap fast thinner here) that could get expensive. Basically a good visual inspection should show up any major flaws, use a magnifying glass to inspect with you'd be surprised how much more you'll find.

Pj, I'd try TIG welding your new pan if you have access to a TIG welder you'll be much happier with the results. If not go over it with an oxy-acetelyne torch with a small tip. I've run engines that were pushing the tach needle over 10 grand at the end of the 1/4 mile dragstrip and never had one crack because of flexing. If you're turning that kind of rpm's and getting flex out of the block then maybe it's time to think about a beefier block. I was running a Donovan aluminum hemi and it was a very sturdy block. Unless you're doing the go fast turn left thing then of course you'd need water jackets.

Yes guys please let me know how things turn out. Don't worry about welding on submarines they x-ray the welds on those so you wouldn't find the leak the hard way, it'd show up on film before it hit the water. I haven't welded on the hulls but had to get inside one once and do some TIG welding on some of the piping in one. And I don't mind telling you I don't want to be in one again either.

Good luck

Blondie

[arcdawg]

when i was doing the kitchen hoods exhaust ducting it MUST BE LIQUID TIGHT and i did ove 30 restruants and NEVER FAILED S INSPECTION and i tacked the **** out of them !!

i was running a 135 mm with fluxcore i just ran it NICE AND HOT and always gave it the once over before i threw the welder back in the truck !!

brian

[KS2K]

Cheap Lacquer Thinner

Go to a Auto Paint supplier. I get mine from the PPG store. Its only $22 for 5 gallons. Cheap thinner, good for clean up. Would not use it as a reducer for paint. But at those prices a 5 gallon can for leak testing could be used over and over.

Paul

[Paul Seaman]

Blondie:
We are a pro4 dirt team, 2.0 ford from a pinto building over 280 ponies at the rear. This car turns 17 sec, 3/8 mile laps and the stresses are not internal I meant from outside either we are hitting debris or dragging it in the dirt. Sorry for the mistake in representation. The block is solid the pan is flexing I think, but I can't prove it.
Peace

[Blondie_486]

Pjseaman,

I just had an image of a fuel altered or a gasser blowing through the traps at 9 grand. I wasn't sure what kind of racing you were doing. I gotta hand it to you getting that many ponies out of a pinto motor.

Good luck and keep me updated on the oil pan project


Blondie

[Paul Seaman]

Blondie:
You know I will, Be good be safe
Peace