Have searched the forum extensively for clues to replacing both the feed and return lines for the self leveling rear suspension on my 83 300TD wagon and was able to find only some limited help.
At any rate, I had a leak in my return line over the rear axle which I ended up replacing a 6 inch section with high pressure fuel line and double clamps on each end.
I just ordered and received from the dealer new lines along with rubber grommets and clamps to secure the line to the chassis. By the way, the new lines are curled up in circles and will need to be bent to follow the chassis, go up over the rear axle and into the controller.
Don't want to try this myself in my garage with ramps and jack stands. I have a local mechanic who is at least used to fabricating and installing brake lines, but he doesn't want to commit his time and hoist if it might get quite complicated. His main concern is if the rear subframe would have to be dropped to fashion the line over the rear axle.
My question is, does anyone have experience with this so as to know how involved a process this is and, whether the frame has to be dropped, and about how long it shoud take?
Any input would be appreciated. My goal is to have this done by 11/24 for a Thanksgiving weekend trip.

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83 300TD wagon
87 300TD wagon
89 BMW 325IX

Line replacement using a lift should not be a big deal. You don't have to drop the subframe to accomplish it. The lines on my wagon were replaced about three weeks ago by the PO. He had access to a lift but said it was an easy (though messy) job. Because the leak had dripped hydraulic fluid all over some of the belts, a belt replacement was necessary too. Plan for your guy to protect the belts, or plan for a belt replacement.

I believe the system is self bleeding, so once the new lines are in, you should be able to fill the tank with the new fluid and start working it into the system. You can disconnect the little valve on the rear from its linkage and manually move it up and down, that will help bleed the air out. When in doubt, check with the service manual.

You might also verify that the other parts, struts, valves and accumulators are in good shape. Accumulators are a common failure point and aren't very expensive to replace, especially if the car is already on a lift. Symptoms of bad accumulators on an otherwise functional hydraulic suspension will be rock hard ride (as though there were no rear shocks at all, which, if the accumulators are deflated, is exactly the case).

Enjoy! I'm kind of proud of the hydropneumatic suspension on my wagon. It is a bit of a maintainence hassle (needed a new pump recently too), but it works as advertised, and gives the wagon a really confident feel, even heavily loaded. Its one of the things that makes our TD more than just a sedan with a big butt.

peace,
sam

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"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)