Rebuilding the front struts
You will need a seal kit (there are two such kits, part number 95 650 941 only contains the main piston seals while part number 95 597 221 has all necessary seals) and a slide bearing (part number 96 004 372) to rebuild each front strut. Apart from some common tools, you will also need a 36 mm socket wrench or spanner; a 18 inch (45 cm) "Stilson" pipe wrench; a bench vice (or the pipe wrench at least); a 6 mm (¼ inch) diameter steel bar or pin punch of about 8 inches long; a propane-butane gas blowtorch (not an oxy-acetylene one) or another heat gun; and some Loctite or similar thread lock.
First, clean the wheelarch by hosing it thoroughly with water and let it dry overnight. To remove the struts, jack the car up, support it on stands and remove the roadwheels. Depressurize the hydraulic system; there is no need to remove the spheres or undo any screwed pipe connections. Put a plastic bag over the brakes and secure it in place with a piece of wire.
Next, pull off the rubber cap on top of the strut. Loosen (but not yet remove) the nut with the 36 mm socket and a big tommy bar. Undo (but not yet remove) the pinch bolt at the bottom of the strut mounting (by the wheel) and the three strut locating nuts on the inner wing. Now remove all nuts and bolts undone and pull off the two rubber return hoses from the pipes in the wheel arch. Gently tap the top of the strut so that it moves down and becomes loose in the sphere support, then grasp the base of the strut and twist it loose from the lower clamp. Finally, remove the strut assembly from under the wheel arch. Note at this point that the sphere and its mounting should be untouched and left resting on the inner wing.
Next thoroughly degrease and clean the whole assembly and seperate the rubber boot/top mount from the strut body. Don't worry about any dirt entering it at this stage, because it will be stripped and cleaned anyway, and a clean exterior makes it so much easier to work on.
To dismantle the strut, grip its body in a vice and using the pipe wrench undo the brass slide bearing on the top of the strut (the one screwed into the top of the strut body, not the smaller brass collar fitted onto the shaft!). If you prepare two halfshells fitting nicely over the strut body (just use 4-5 inches of a 2 inch waterpipe separated into two halves), you can grip the strut in the vice without damaging it. The thread is a normal right-hand thread, but it might be so tight (especially as it is locked with Loctite) that you will have to use a gas blowtorch on it for about 30 seconds or so to help loosen it. There is about an inch of fine-pitch thread there, so it will take a bit of turning to get it out. Carefully drain any remaining LHM out of the strut while holding the parts together, finally, withdraw (carefully! they will be quite loose when they come out!) the internals which comprise of spacers, bushes, piston rods, and bump stops, and note (possibly by making a sketch) which order they were assembled in.
The steel nut at the bottom of the shaft has to be undone as well to fit the new slide bearing, and this one will be very tight, too, so the blowtorch might help again, combined with the 6 mm pin punch (through the oil hole) while gripping the nut in the vice.
Once everything is out, thoroughly clean and degrease it all, including the inside of the strut body, as there will be loads of contamination in here. The rubber return hoses might remain attached all along but if they need replacing anyway, this is a good time to do it.
Before re-assembling, apply a thin coat of silicone grease (grease, not silicone spray!) to all internal working surfaces. Compare the removed and the new parts to see where the wear was. All the parts you need will be in the two kits listed above but the most important ones of all are almost hidden: after removing the smaller steel piston rod from inside the main strut shaft (the medium sized piston rod, not the smallest one at the very bottom), look inside the bore of the main piston shaft and you will see a small, white teflon sealing ring a little way up the bore. This is the main piston seal, and when it is worn it is the cause of all the hesitation and jumps when raising or lowering the suspension.
If you find the piston rod itself having stains or even rust, you might consider polishing and cleaning it very thoroughly. Use a thinner first and lots of elbow grease. Then fill the pits with hardening plastic putty and finally polish it until it is really smooth and even.
The creaks, groans and LHM leaks in the suspension are caused by wear in the bronze slide bearing and its rubber seal, but if this little ring is worn, the pressurised LHM just leaks past it and into the return system (this is the reason for both poor suspension performance and the return line popping off easily). So, remove the old seal carefully, taking care not to damage the bore (use a soft tool, toothpicks, for instance, are excellent), and fit the new ring into place very carefully. This job is a little bit fiddly and awkward, but take your time and use a soft plastic or wooden tool (old toothbrush handles are perfect) to push it into place and seat it properly.
When fitting the new bronze slide bearing onto the piston shaft, you might need to use a tiny bit of moly or silicone grease on the felt wiper seals to help them slide smoothly on. It's very easy to kink these seals and pull them out of their seats when fitting the bush on, so observe them as you do it. The shaft should not stick, even lightly, when fitted into the slide bearing, so if it does this, it probably means that the felt wiper has come off its seating. Refit the new rubber bump stops, bushes, and sliders in reverse order, and use Loctite thread lock to secure the steel nut on the bottom of the piston shaft.
When re-assembled, pour about 20 cc of new LHM into the strut to lubricate it, and assemble the parts inside. Use Loctite to hold the slide bearing in place while you screw it back in.
If the strut fails completely, it leaves lots of metallic debris in the hydraulic system. Flushing and replacing the LHM is required in this case.