Crusty but loved W124, learning to weld advice?

A word of warning about w124's, they hide rust very well. The underbody protection is very thick and will still look solid even though the metal behind is long gone.

Before you start have a good poke around the 4 jacking point tubes in the sills, the floor underneath the rear seats particularly under the central locking pump, the rear subframe front mounting point inner edges, the floor under the drivers seat base rails, and the front crossmember between the wishbones.

Other areas like under the washer bottle, front wings, and the estate section side window rails will be more easy to spot.

ace thanks, there's some really handy tips there.

i had the rear subframe mounts done when i bought the car, so presumably they are still ok. I did have an old merc specialist check over the car when i got it 7 years ago, and at the time that was the only rot. I've had someone waxoil it underneath every few years, but i have kept it outside most of the time since.. so who knows what else lurks!

Remember everything in a car is flammable, carpet/underfelt/underseal/waxoil so weld a bit and check for fire or smoke and keep something handy to put a fire out!

The other thing worth having is fire blankets, they are not expensive and ideal for draping over stuff like seats/plastic trims/paintwork that you don't want burned by welding sparkles or grinding sparks

My bits of advice are, get a decent auto-helmet, get a decent set of gloves, and get plenty of light.

I always find its amazing as much as you need to look after your eyes, you still need to see what you are doing to achieve a neat weld in the right place. Screwfix or Toolstation sell good enough auto-helmets. Means you don't have to worry about holding a mask or moving your head to blacken the screen. Always keep your screen clean as you'll be amazed how much detail you lose looking through a dirty screen.

Have plenty of light to begin with too so that you can start in the right place and the contours of the metal are obvious through the darkened glass. Daylight is best but a good indoor light is ok. Sometimes shadows can confuse you too.

The gloves will protect you from sparks that although aren't a major issue, can put you off keeping your hands steady of you aren't used to it.

Other than that, practice practice and watch plenty of Youtube. Learn to spot a good weld, and how to get things neat. This will then make it alot easier to clean up afterwards - see TonyBMW's advice. Start with thicker stuff, then when you move onto thin stuff, start with a series of spots eventually joined up to minimize distortion. By watching Youtube, you will also learn to spot when things go wrong, like incorrect gas, lack of gas, bad torch tips, incorrect current, incorrect wire speed etc etc.