What do you guys use to tell if a weld leaks?

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Hey guys, new to the forum here.  I've been searching around for a couple days for some kind of dye or something of the like tha you can use to detect a leak in a weld.  I've ran across some machinists dye that says its for valve work to detect if the valve is seated right and whatnot.  And I did see some Magnaflux dye but it was very pricey.  The reason I was asking is I took a piece to be welded to a shop several years ago, it was actually a bov flange that I needed welded onto an intercooler pipe, and the guy there had some kind of red dye that he put around the inside of the weld to see if it leaked out anywhere.  In the near future Im going to be working on an exhaust piece that comes right off my turbo and bolts to my downpipe, and I want to be sure that I dont have any leaks.  What do you guys recommend?  Any sort of home remedys or backyard mechanic ideas could be suitable as well.  Im just not looking to drop 80 bucks on some Magnaflux dye. Thanks, Chris
Reply:Duct tape, LOW air pressure, and soapy water in a spray bottle. A extra set of hands is helpful sometimes too.If you cant fix it with a hammer, it must be an electrical problem."Boy, everyone starts with a full bag of luck and an empty bag of experience. The trick is to fill the bag of experience before the bag of luck is empty."-Grandad circa 1990ish
Reply:For your application, a good look with a magnifier would be plenty.My name's not Jim....
Reply:Like Larphead says.  However, if it's not something that you can pressurize, flood the area with lacquer thinner and check the opposite side.  That definitely works with valve to seat interface.  You do have to put some tension in closing the valve.  Lacquer thinner will make its way through the smallest of cracks.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:The magnuflux brand dye checks for cracks.  There are different brands.  The old school way was to wipe the area with a rag soaked in kerosene.  You then wiped the area clean and dusted chalk powder on top.  If any kerosene was sitting in a crack the chalk dust would show the wet area.   It was troublesome because now you have contaminated the area with kerosene.     The modern solutions and developers and more effective and clean up without contaminating.  Some even require the use of a "black light" to show up the solution.  I am not sure how much is shown in the way of a leak.  It certainly shows cracks and porosity.   Checking for leaks with 2 or 3 psi and soap solution is more practical.
Reply:You can mix a small amount of oil (Marvel Mystery Oil is great) with lacquer thinner (and add a small amount of machinist's dye or anything else that is oil soluble and highly colored, if you have it), spread that on the weld and let soak in a minute, then quickly and carefully wipe the surface clean. Immediately dust the surface thinly with a white powder; I think talcum is fine but even flour will do if you can dust it thinly.If you have cracks or pits, the solvent et al will seep into them, then creep back out after the cleaning and be adsorbed by the powder, changing its color or appearance. A coloring agent makes it more sensitive. Too much powder hides the results for a small crack.
Reply:I use a old inertube and hose clamps. Use part of tube that has niple and spray with soapy water.You are not going to get a high presser test this way but you dont need one.
Reply:Welding correctly the first time and knowing what you are looking at while doing it is the best leak preventer there is......zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:The old school way was to wipe the area with a rag soaked in kerosene.  You then wiped the area clean and dusted chalk powder on top.  If any kerosene was sitting in a crack the chalk dust would show the wet area.  Diesel works too. Spray it on one side, if the other side apears wet you have a leak.Classic 1D 200SAE 30086 SA 200Hyperthem 45Jancy Mag Force O/A Victor-GossCable's remote2-12" Mathey Dearman bevelersLN 25Miller Auto Set 211Wendy's Pancake/Jackson PipelinerNew Holland LS 180Great story man....tell it again!
Reply:What you may be lookin for is called 'visible' Liquid Penetrant.  This is usually a bright red dye and comes in a kit of three cans:- Penetrant- Solvent (to remove excess penetrant and overspray)- Non Aquaous Development (white chalky spray)In practice, you clean & degrease the surface to be inspected.  Final cleaning with some of the solvent on a damped paper towel.Spray on the dye penetrant and let it dwell for the time specified on the can - usually 3 to 15 minutes.Using several paper towels, wipe off all the penetrant - totally; you don't want to see any red - anywhere.  Final clean up is done with paper towels dampened with the solvent - keep wiping until no more red/pink colour comes from the part.Spray on a light dusting of the white developer.  Immediately have a look at the part; you're looking for the big bleeders!  Those cracks or voids that have trapped a lot of penetrant.  You may have to carefully flush any big bleeders out with solvent and clean again before you can proceed.Spray on some more developer until you have an even thin light coat,  Wait and watch.  You are looking for the red penetrant to bleed out into the white developer.  Finer cracks may take up to 15 minutes to show, coarse, more open cracks, laps, voids wil show more quickly.This techique is very sensitive but it is also very messy! Usually a low pressure air test or vacuum draw is used to find any big leakers before going to liquid penetrant.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Thanks for the replies guys, I'll give them a shot and see what works best.  Hopefully just welding it good the first time will work better than the rest.