Abs pump DIY repair

[E92 m3 South Africa]

Hi guys,
I recently had the dcs warning light come on in my 2008 e92 M3. The BMW repair centre quoted me R40 000 to replace the complete pump assembly and advised me that the part was not repairable. I spoke to many technicians and they also agreed. I decided to strip the part and see for myself if this was true. The first step was to disconnect the negative battery terminal. Then I removed the plastic covers near the wiper blades(8mm bolts). This is where the air conditioner filters are housed. There is also the wiring harness that needs to be moved a little, this is located just behind the air-box. I siphoned out as much brake fluid from the brake reservoir that I could. The pump is located close to the driver's side wiper blade. After removing the steel brake lines, I unplugged the electrical connector. There is a locking clip that must be pulled up before this connector is unplugged. There are 10mm bolts securing the pump assembly (3 off) I used a 10 mm socket with an extension, I used a telescopic magnet tool to lift them out of position once they were unscrewed. It was a bit of a squeeze to get the pump assembly out. The DC motor looks like a small windscreen wiper motor. There are no bolts holding the motor onto the pump assembly as the aluminum of the pump assembly is crimped over the motor flange. I used a 20 mm end mill cutter to machine the crimped aluminum that was holding the motor housing. I then separated the motor from the pump assembly. There are two places on the motor housing that are pressed in. These need to be drilled out carefully, without drilling more than is required ( to avoid drilling into the motor internals). I used silicone sealer to seal the holes after assembly. The motor shaft is a little off set like a cam, this creates a pulsing action when it spins and pushes 2 opposing plungers in and out. Then I removed the armature and brush assembly from the motor casing. I inspected the carbon brushes and their tension, this seemed ok. The car odometer is presently on 95 000 km. I used "Spanjaard lectro Kleen" and sprayed the inside of the motor thoroughly, including the brushes and the brush holder. The carbon dust causes the electrical current to track inside the motor. This causes the on board computer to trigger the DCS fault. I assembled the motor after drying the internals. I then drilled and tapped 4 holes on the 4 corners of the motor flange ( the area that was machined) I used a 3,3 mm drill bit and a 4 mm tap. I was careful not to drill more than 10 mm into the pump assembly as this would reach into the cavity where the valves operate. I used 4 mm mild steel cap screws to attach the motor flange onto the pump assembly. I made up two mounting adaptors out of aluminum as there is valve cavity directly below the motor flange in two places. (see second and third pictures) I then assembled everything back into the car and topped up the brake fluid. I sent the car to BMW to bleed the brakes as it felt soft. They have software to activate the dcs system and bleed the brakes at the same time. They were very surprised that I resolved the problem and did not even charge me to bleed the brakes. I have a strong feeling that BMW Germany is aware of the carbon dust causing problems with the dcs system. This is why they have tried to make it difficult to strip and clean the motor. They knew that the throttle actuator on the v10 M5 was faulty and they still used the exact same part on the v8 M3, they only changed the part number. The cost of the dcs repair was less than R300. (20$) This is what the drill bit, the 4 mm taps, 4 mm cap screws, the electric cleaner, and the 20 mm end mill cost. I have been using the car for about 2 months now and the dcs light has not come on again.

[Theodore]

Wow, I'm impressed, great contribution to the forum! Thanks for the write up. If I get this fault code, I will definitely be following this DIY. Any chance you can upload photos of your finished work with the screws?

Now if you can only find a $20 long-term DIY for the throttle actuators...

[admranger]

Nice work!

Is there a way to clean the carbon out w/o machining the pump motor housing? Perhaps drill two small holes, one on each end and spray the cleaner in one end and it can drain out the other?

[E92 m3 South Africa]

Thanks. I will be posting pictures in the next couple of days. I just need to figure how to download pictures from my i phone to my I pad. A guy from the UK sells replacement gears made for the throttle actuators made out of brass. They are machined very well and work perfectly. I replaced mine, but cost me a lot, converting Rands to Pounds.

[E92 m3 South Africa]

Thanks. I think it is possible to drill two holes and flush the motor. The only concern is that you would not be able to inspect the condition of the brushes and their tension. The motor also has two magnets in the housing around the armature. You would need to know the exact position of these magnets to avoid drilling into them. You could drill on the side of the motor anywhere, not more than 10 mm from the top of the motor, and anywhere on the side of the motor, not more than 10 mm from the base of the motor. (Preferably on opposite sides)

[cnasher]

Did you happen to measure the brushes while you were in there? I have seen repair kits that include new bearing and brushes, but shipping will be quite lengthy timeline. Has this issue returned. My car is low mileage, but it sits a lot so I suspect this worsens the problem. Seems worse the warmer the weather. I am at a point now where this issue is persistent

[cnasher]

I managed to complete this rebuild over the weekend. I ended up installing 13mm length brushes and they fit fine.