Brake Bleeding/fluid change 128i Convertible

[JimD]

I don't think it makes a difference but my 128i is a convertible, e88. I read the brake bleeding topic for the 135i and it is good. I don't want to repeat everything said there but I thought some might like a piece on the 128i.

A key difference is the size of the bleeding screws. The front on my 2009 is 11mm and the back is 9mm. Special wrenches are normally recommended that are closed six point wrenches with a slice out of them so you can go over the brake line (or the fluid discharge hose in this case). I couldn't find them in the right size so I just put the closed end of a combination wrench on the bleeder valve before attaching the hose. This worked fine. I could not reposition the wrench on the back but it would come open enough. The front could be reposition.

The main work in this is getting the car up on stands so you can remove the wheels and access the bleeders. If you can do that, you can change the fluid. I roll up on 2x4s on the front so I can jack in the center and reposition both from sides on stands (using little plywood blocks in the pockets) with the rear wheels still on the floor. Then I jack on the differential (not the cover) to do the back.

To do this, you need a Motive 1 man brake bleeder, some new fluid (I used Dot 4, a liter should be enough), a piece of clear hose (smallest you can get at the home center or maybe one size bigger (get 2' of each if you can), an old soda bottle (I used a 2 liter), and a turkey baster. You also need the jack and stands and preferably 1/2 inch torque wrench for the wheels.

After the wheels are off, I sucked all the fluid out of the resevoir I could with the turkey baster blowing it into the 2 liter bottle and then filled the resevoir with the new fluid. The normal process with the Motive is to put the fluid in it but I didn't want to clean it out so I just filled the resevoir. You have to refill it every couple wheels but it works fine. After the resevoir was full, I hooked up the Motive and pressurized to 10 psi. Then bleed the passenger side rear, then the drivers rear, then refill the resevoir, then the passengers front, then the drivers front. When you want to disconnect the pressurizer you want to unscrew the cap on the Motive to relieve the pressure. I think that is much more important if the Motive has fluid in it but it's a good idea even doing it my way.

I did not have fluid with a different color so I let it run 2 minutes per wheel. I do not know if that was the right amount of time but it seemed reasonable. And I used up almost a liter of fluid. Probably too much on the front and maybe not enough on the rear but I figured the fluid in the fronts got hotter so it needed changed worse. Some people apparently put food coloring in brake fluid but others point out the food coloring has water in it which is really a bad idea in brake fluid.

Jim