No matter what vehicle brand, a vehicle’s exhaust system is one of the most frequently repaired parts in the course of its lifetime. It could be as simple as replacing a rusted-out joint or replacing entire sections. Professionals swear by TIG welding as the recommended process for welding thinner gauge and tubular metals.
While TIG welding is recommended, it is not the preferred choice, especially with DIYer’s and garage monkeys. MIG welders reign as king when it comes to preference, as the MIG welding process is easier to master, set up, and ultimately cheaper than TIG – while producing great results.
To cut the story short, we will be talking about everything necessary that you need to know when it comes to MIG welding exhaust pipes. The appeal of MIG welding when it comes to thinner gauge metals is its ability to produce clean and robust welds without burning through the sheet.
Let’s get to it then.
Before you start
Welding is pretty much permanent when done, so it is best to do a dry-run project before committing the first bead. Doing so will familiarize you with how you will tackle the project. Also, welding is a power-intensive activity. Practicing will help lower down your power bills by ensuring you get it right on the first try.
Going through the motions will help identify problem areas in terms of how you will position the gun. For example, finding out that a particular path is awkward mid-weld can be dangerous or produce a lousy weld.
During this time, getting the MIG torch or gun’s feel is optimal, especially if you will be using the machine for the first time. Furthermore, getting the equipment and materials together needs to be done in this stage: your welder, gloves, mask/shield, cutting tools, and C-clamps should all be available.
The weld settings
The settings will vary slightly depending on the machine, so make sure to go over the instruction manual. Better than that, the welders will have a chart on the side that will contain the information.
Three things need to be in synergy regarding settings: the voltage, wire speed, and gas mixture (if applicable). In addition, there are a ton of setting tweaks specific to the welder itself, the type of steel, and the thicknesses involved. On this note, your welder of choice should allow for voltage fine-tuning as well as a wire-speed selector that could match.
We do not want to bore you with a long table full of charts and numbers, so we decided to direct you to this link.
Clicking on it will take you to a super-handy online welding calculator that automatically applies the values you want. It just needs what kind of metal and the thickness you are working on, and it will give you the setting values you need. Of course, by then, it is an easy matter of replicating the settings on your welder.
Cutting and preparing the metal surface
The exhaust system is located in one of the most challenging spots to weld in because it is underneath a vehicle. Even shops with a vehicle lift will still encounter awkward positions when attempting to weld while the exhaust system is attached.
The most practical and safest way to do welding repair on the exhaust system would be to cut it out and remove it from the chassis. When done this way, you can work on it in the relative comfort of your workbench or table. Remember to measure twice or thrice before cutting the pieces to avoid any wastage and frustrations.
Surface preparation is key to solid and clean welds, and to achieve this, use abrasives to ensure that you remove all the rust and oxides from the metal surface. You can use a steel brush, steel wool, or a grinder if the buildup is too much.
If you’re looking for an angle grinder to help prep your exhaust pipe for welding, we recommend this DEWALT angle grinder. It’s a proven tool that will cost you just under $90.
Do not overdo it though, remember that these are exhaust tubing and parts and therefore made of thinner gauge metal.
Upon removing visible rust or any other imperfections, wipe the surface down with an industrial solvent like Acetone. The application will remove any oil stains or grease that is on the surface to be welded. A thoroughly prepared and cleaned metal surface is a must for any successful welding job.
Positioning and clamping
After a good cleaning, the next step is to assemble the pieces according to where they will go once permanently welded. An excellent place to do this would either be on a workbench or a table. Once you have the pieces aligned, break out the C-clamps to hold the pieces temporarily in place.
When you are at this stage, fitment and the accuracy of the cuts are paramount. Remember that this is the last time that you can still move the parts around. Mark the areas as you align them so that they are perfectly aligned when you clamp them.
C-clamps will hold the pieces together before doing any tack welds; after the first welding bead forms, it is pretty much permanent. While the clamps are temporary, the parts would be the same when joined permanently, so do be extra careful when using the clamps.
The SOLUDE C-clamp set is perfect for a project that involves varying sizes and widths. A sturdy ABS plastic shell protects the set of four clamps for just under $40.
Tack/Spot weld
While the C-clamps hold the pieces together, make a small Tack weld on strategic places corresponding to the attached C-clamps position. These tack welds are advisable because of the thinner gauge metals in use. Tack welds should be the first step because they can be easily removed even when mistakes happen.
Moreover, there should be around three to five tack welds around the tubing, as these would replace the C-clamps position when removed. After the tack welds, it is time for the more permanent spot weld to join the pieces into one solid part.
At this point, warping may occur on the opposite side of the tube, but the heat produced by the welding process itself will make it easy to bend back into shape.
Completion of the weld
Completing the weld simply means covering the gaps entirely with spot welding until full coverage is achieved. The complicated part is ensuring all gaps are covered to eliminate leaks. The best way to achieve this coverage would be to weld over the spot welding beads instead of stopping on one and continuing to the next gap.
Because it is MIG welding, there is little clean-up after a weld pass as there are no slag deposits. On top of that, you will surely finish in record time as MIG welding is among the fastest processes.
Wrapping it up
Exhaust pipes are generally made of softer metals, and some are alloys and require fine-tuning when it comes to welding. The recommendation is to choose the right MIG welder that allows minute adjustments to both voltage and wire speed settings to hone in on what works best for the metal being worked on.
Welding utilizes very high heat and electricity to join together pieces of metal and can be quite dangerous. Therefore, proper ventilation, protective gear, eye protection, and presence of mind should always go hand in hand on any project involving welding.
