On my W123 body

Crack approx. 2 “ length has been found on
big cross beam.

This big cross beam is welded between left frame
and right frame and located under engine near oil reservoir.

How can I repair this crack by gas welding?

I think electric arc welding is not acceptable because
may be arced between engine bearing and crankshaft or on bearing wheels etc.

If you use a stick welder and connect your ground lead on the crossmember itself, the energy will only conduct between the ground lead and the electrode.

There is a chance of blowing electronics because of the power surges, but I believe that the chances are remote. You will not do things like welding bearings together.

I was about to say that I had not arc welded on a complete vehicle since my Chevy van of the very early seventies. But now that I think of it, I welded up a crack in the muffler on my 240D some years ago with it in place. There again, I connected the ground lead as close to the point of the welding as possible.

Good luck,

thank you