I was troubleshooting a puzzling fuel flow problem on my 230SL. Grasping at straws, I wanted to remove the pipe from the fuel filter to the injection pump to test it for obstruction. When I tried to loosen the swivel nut on the cold start valve connection, the male fitting on the pipe broke off. Most of the fitting remained in the swivel nut on the CSV line. I removed the CSV line and buggered the cone nipple trying to remove the remains of the pipe's fitting. I was able to save the swivel nut.
Replacement CSV lines are available for around $150 plus shipping, which would require a giant box.
So I found replacement cone nipples for $1.99 on Belmetric.
https://belmetric.com/solder-cone-nipple-uncoated-plain-steel-cohline-series-9010/Belmetric also has swivel nuts.
I cut the CSV line close to the end, and filed off the remains of the brazing of the nipple to the line until he replacement cone nipple would slide over the line. Then I cleaned both pieces with acetone, applied flux, and soldered the cone nipple to the pipe with plain old plumbing solder. Cleanliness is key here.
I installed a new filter-to-pump pipe that Gernold supplied and reinstalled the CSV line and went on about my troubleshooting. The problem seems to have been a weak fuel pump but with some strange symptoms that I may put in another Topic.
Anyway, this is an option if you need to repair a line or fabricate a new one. Steel fuel line is available in various metric diameters online and at parts stores.
Picture of repaired line attached.
Cheers,
CT