Finally worked on rear subframe

[Fastcar155]

Got it off. It's very heavy, around 100kg+ I reckon. I can only just lift it about an inch off the ground.

You can see with it rolled over how bad the corrosion is.

(Images clickable, bigger images)

Hi , are you sure that is rust rather than stress cracking?

 

[Justintyme]

Like a duck to water, surprisingly.

Apparently Gas less is sometimes better than CO2/Argon outdoors as the shielding gas just blows away outside whereas the flux produces the gas right at the point it's needed most.

I had a bad experience with a stick welder a few years ago (I just couldn't do it, couldn't strike and maintain an arc so gave up), flux core in comparison is like child's play. With some research and practice to understand min/max volts/amperage and feed rate, etc. I was able to judge when I needed various settings and what to expect etc.

During my practice week, I had thin sheet metal (old microwave shell) and "infinitely" thick old brake disc to practice with, so got to know from the extremes the properties of thin and thick metal. So I got to practice how to not blow holes through the thin metal, and how to get good penetration in the thick metal. I was able to test strength by welding the end of a 10mm rod of steel to the disc with a butt joint, then levering it to test its strength. I welded bolts to it and tried hammering them off, they just bent over ... So I got to test welds to failure to figure out when you've got a bad weld with little to no penetration.

I got one spatter drop go through my pants and have a dot on my leg as a result, but it didn't really hurt. If I wear these pants to work again, people are going to think I'm a stoner. What did hurt was the shard of metal from grinding (I had a face shield on, but somehow something got past it, probably from below) embed itself in my eye on Saturday. I couldn't see anything obvious in my eye, but I could feel it, so I assumed it was just a scratch. Today it wasn't getting any better so I had a proper look in the mirror with my camera zoomed in and saw a dot of metal near my pupil, so went to the eye hospital after my attempts to flick it off with the corner of a credit card failed as I couldn't get near it without girling out. They numbed it and got it out. I'll invest in a better face shield in future!

I've little to compare the welder to, but I've already fixed a few things, and also bought 2 new rolls of flux core which turned out to be very low on flux. I assumed they'd be an upgrade to the stuff that came with it, but instead it was nasty and horrible to use (yes it was definitely "flux core", not regular mig wire). It left no residue, unlike the stuff that came with the welder leaves a white powder you brush off, evidence of the flux. I put the original stuff back in which is much nicer. So money well wasted as I got to experience the difference between different qualities of wire.

I'll update my original thread with pictures, etc shortly. I spent 6 hours this evening refitting the subframe, shocks, brakes, prop shaft, arch liners, sensors and exhaust, then went for a 20 mile blast test. The tracking should in theory be out because I've had the arms off and didn't record the position of the adjusting cam-washers, but it feels totally normal. I'll get it tracked, but right now, the car is totally fixed. So I've very pleased. It in total cost less than a new 2nd hand subframe and I've now got a welder and new skills out of the other end.

What's your welding experience?

I've spent many years working in a body shop Mike, so would be familiar with brazing, soldering ,ARC , Oxy-acetylene and of course MIG welding, Of all of them , the MIG is the easiest one. But whereas you will get sparks etc from most kinds of welding, what comes off a MIG weld is literally molten metal...not surprised you have a hole in your trousers,,,and a skin burn too!!! Even leather welding aprons are not MIG proof. I felt a shudder run through me when you mentioned the "Foreign Body" in your eye....I had very bad similar experience myself. But as it happened on a friday evening, it stayed in my eye for the weekend...and by Monday morning when i went to the Doctor , he took one look and sent me straight away to the eye specialist in the Hospital. There after followed 11 months of agony, 5 operations, and the news that the sight was gone. From the time the particle got stuck on the eye until it was removed,ulcers developed on the eye, and if you have or know anyone who suffers from ulcers anywhere on the body, they are extremely painfull.
Glad to hear that you are happy with the car now, and have acquired skills which no doubt will come in very handy in the future But the bottom line is why a quality ( I use the term advisedly ) produce an important component which is prone to rust and failure. Chances are now that after your repair , its much stronger than the original.

 

[Justintyme]

Hi , are you sure that is rust rather than stress cracking?

In this case with these subframes, first the metal rusts and weakens, and then the (normal ) stress and strains finish the job.

 

[daveenty]

You do realise that this thread is nearly 3 years old guys?

 

[Justintyme]

You do realise that this thread is nearly 3 years old guys?

You do realise that this thread is nearly 3 years old guys?

You're right LOL...None the less, I dont think that we have heard the last of rusting MB subframes,,,,they were very prevelant in the 211's, but I seem to remember a case of one in a w212...

 

[Fastcar155]

Certainly is

Hi , well I am having my 2016 C 207 checked very soon for rust and front and rear subframe cracking .Just to make sure inspection of brake pipes will also take place.

As this car is based on the W204 just want to make sure all is OK.