Note: This only applies to vehicles where you are sure the PS reservoir has no cracks, and the hoses are in good shape from what I have gathered it is a pretty stout piece, and isn't prone to cracking like our expansion tanks. Most replace them because they are cheap comparatively, at 40 bucks for Genuine BMW, or ZF (OEM) for around 25 bucks. My 2003 has 71k miles and the reservoir is basically brand new, hoses going from the reservoir look good as well, not dried out or cracking. This DIY is performed on a 3.0 M54, but process is similar for V8 models. Obviously I am not liable for any damages to your vehicle when following this procedure.
You will need:
1 - Quart of Synthetic ATF (PS fluid, I used Mobil 1) or if your cap says CH-11S on it, use that ($5.99 for Mobil 1 ATF at WalMart)
1 - Size -130 O-ring, pick your poison as far as material goes, personally I used a Fluorosilicone O-ring (military rated, higher temp and chemical resistance than Viton, and its blue! lol) from McMaster Carr, $3.50
2 - Stainless Steel worm drive hose clamps, I forget the sizes but somewhere in the 7/8" range, just measure the diameter of the hoses first, if you prefer your clamps not to "bite" into the hose you can use fuel line clamps which are smooth inside
Tools:
-Utility knife or PVC pipe cutter (great for hose trimming)
-Socket driver or screwdriver for hose clamps
-Turkey baster or siphon for draining reservoir
-Socket for mounting bolts of PS reservoir
-Drip bottle for catching old fluid
1) Open the PS cap, remove o-ring by picking it out with a small knife or screwdriver, throw old o-ring in trash, lubricate new o-ring with fresh ATF or CH-11S, install on cap in groove, set aside for later.
2) Take your turkey baster ($1 at dollar store, then you can throw away after and your wife won't get mad), suck out all fluid in reservoir
3) Unbolt reservoir off its mount, now you have some room to work
4) Use flathead to loosen clamps on bottom of reservoir, place drip bottle underneath, and remove hoses from reservoir 1 at a time, catching the drippings from the reservoir into your catch bottle, and draining the fluid from top of the hose, remove old clamps from PS reservoir hoses
5) Take pipe cutter or utility knife and cut approx 1/2" off the ends of the hoses, make a clean cut and expose a fresh hose end, slide new worm gear clamps over hoses
Optional Step from Miniz Guy if you'd like to replace your hoses but don't want to buy factory ones for $60:
On E36's, the hoses are 1/2" ID. Use transmission hose rated for high pressure applications and you can replace the original hoses for about $10. Cut the original crimp off, but not into the barb, and slip the new hose on with another worm clamp.
The process should be the same on the X5. A little better way that using the old hoses.
6) Reconnect hoses to bottom of reservoir (they are different sizes so you can't mix up), tighten clamps with screwdriver or socket, now is a good time to wipe down the 2 hoses with degreaser, and use a rubber protectant on them, I use 303 Aerospace protectant on rubber items
7) Bolt up reservoir back to its mount next to the Oil filter housing (on 3.0 models), and refill with fresh ATF. There is a dipstick on the cap which has a clear marking for the correct level, don't overfill. Put your cap with new o-ring on the reservoir and check level.
8) Start car, do a couple lock to lock turns, then shut car off and check level on dipstick. Remove some fluid with siphon if too high, add some if level shows low. Obviously check for leaks on bottom of reservoir, but as long as hoses were in good shape, you should have none as long as you exposed a fresh hose end and used new clamps
10) Have a brewski and enjoy not having to mess around with your PS system for a few years!
I have to give credit to bluebee and others at Bimmerfest for the O-ring sizing on the reservoir, this DIY is inspired by their threads and helpful information on the M54 engine, and I thought I'd pass along the information to my fellow Xoutposters, with some preventative maintenance and inspection, a half hour of your time and about $10 in materials, this is an easy procedure to perform if you are doing an oil change or something similar. Hope this is helpful to some!
