Pre requisites:

1 - Decent diagnostic cable and software. I HIGHLY recommend cable-shack.co.uk Jimmy is a fantastically helpful and friendly guy who is always on hand to help.

After installing this software I was able to ascertain the following fault codes: 5DF0, 5DF1 “DSC: Hydraulic unit: pump motor connector faulty". Apparently this is almost always down to a fault in the pump/module (as was mine) I used ECUtesting to have mine rebuilt: ecutesting.com

Also the software is required for the brake bleed procedure and calibration of the steering wheel sensor and DSC/ABS unit.

2 - Pressure brake bleeder

3 - Jack and axle stands.

Location.
The ABS pump/module is located on the drivers side, towards the back of the engine bay under the brake servo. Although the the pump looks relatively easy to access from the top of the engine bay, there are obstructions including the brake lines, which would make it very difficult to lift out this way.

Step 1: Removing the Wheel Housing Fixtures

First thing to do is jack the car up and whip off the front, right wheel. Then remove the 11 hex bolts and 4 plastic expanding rivets from the wheel housing. I found it best to get something slender (like a flathead screwdriver) to gently ease the plastic pin head out. Once there is enough clearance the pin can be pulled out by thumb and forefinger. This releases the tension on the expanding part and can be pulled out of the wheel housing completely.

Step 2: Removing the Wheel Housing.

DON'T FORGET! There is a cable tidy clip attached to the wheel housing (see picture annotation for location). From within the wheel arch, push on the back of the clip to pop out it from the wheel housing.

Once all of the retaining bolts and rivets are out, the housing should only be retained by a lip in the wheel arch. Rather than trying to release the housing working around the outside of the wheel arch lip, I found it much easier to grab either side of the wheel housing from the back and pull it into itself the (flexing the two sides of the housing closer together). This is helps to gain enough clearance to remove out of the arch.

Once the housing is off, access to the pump becomes a lot easier. Now the black cradle that holds the pump in place can be clearly seen

Step 3: Draining the Brake Fluid.

Prior to removing anything I drained brake fluid from each calliper. (I am not 100% sure this is proper procedure, but I wanted to avoid as much DOT4 mess as possible). Post unit removal I discovered something elsewhere on a forum: “actuate brake pedal (>60mm) and secure using a pedal pusher. This closes the central valves in the TMC and prevents fluid running out of the open system.

SOURCE taken from a Teves pump repair kit diagram found here: e90post.com/forums

Step 4: Marking the Brake Lines

I decided to mark all lines feeding into the pump. Starting from the back and in order I gave each line a number. This is just for my benefit and ease of re-fitting.

Step 5: Rag Preparation

Once at the stage I was ready to release the lines from the pump I made sure I had enough old rags placed under and around the pump to avoid any spillage and drips.

Step 6: Releasing the Brake Lines From Their Fixing Clips

Once all of the brake lines are released from the pump, release the brake lines them from their immediate fixing clips. This gives more freedom of movement and a little more manoeuvrability when removing the pump. Trace the main bunch of brake lines around the back of the engine bay to a black fixing clip. The clip is retained at the bottom and hinged at the top. The release for the front line can be found in the wheel arch. This was a bit stiff but does ease out of the fixing.

Step 7: Removing the Electrical Connector

The electrical connector needs to be disconnected from the pump, although if this proves to be too tricky it can be detached later. Do remember that on the top is a tab that needs to be fully pulled upwards, to eject the connector. On mine this was a little stiff and I found that the securing tab needed to be pulled almost fully out, before it would release from the pump.

Step 8: Removing the Unit+cradle

The cradle is retained by one bolt and sits ‘floating’ on two pillars with rubber mounts. The back of the cradle retaining bolt can be seen poking out into the wheel arch, unbolt this from the other side, inside of the engine bay. With the brake lines released, it allows more manoeuvrability, as it is quite tricky to remove the unit. The cradle now needs to be manipulated and gently eased upwards off the two mounting pillars. If the electrical connector is still attached, it might make things harder. However if the cradle and unit is lifted off the pillars, pull it out gently into the arch to gain access to the electrical connector. Again do remember that on the top is a tab that needs to be fully pulled upwards, to eject the connector. On mine this was a little stiff and I found that the securing tab needed to be pulled almost fully out, before it would release from the pump.

With the pump out it can be unbolted from the black cradle. One hex bolt on the side and two under. The picture shows how the cradle looks and how the pump comes together to ‘seat’ in the cradle.

Step 9: Seal Off the Connections

Finally place tape over the electrical connecter and brake line ends to avoid any dust or water ingress, whilst the unit is off for repair.

Step 10: Refit the Refurbished Unit

Re-fit the unit, following the steps in reverse order. The brake lines will need to be re-bled and this will require a pressure bleeder. I believe DIS diagnostic equipment should also be used in conjunction with the bleed procedure.

Here are some links to further information about proper brake bleeding procedure:

Video-on-how-to-bleed-E38-brakes-with-DIS-software-bimmerforums

correct-method-bleed-brake-system

In some cases the unit will need to be re-coded with SSS Progman and the steering sensor & DSC unit re-calibrated with DIS.
To do achieve this procedure, follow this youtube tutorial: youtube.com