My 88 E30 M3 has no rear brakes and no fluid comes out if I try to bleed.

[Del Schier]

In an attempt to purge the brake fluid of my 88 BMW E30 M3 I could not get brake fluid to come out of the right rear brake using a pressure bleeder at ~ 20 psi. The brakes discs are shiny and the ABS warning light is not on and I thought the ABS and rear brakes were OK. According to this blog: https://bmwe30cabriolet-wdm.blogspot...-your-abs.html I disconnected the car's battery and removed the relays and connector plug. I then connected both #30 relay pins to 12V+ of a separate battery and grounded pin 5 of the ECU connector. The pump motor runs. On several tries connecting and re-connecting power and pressing the pedal no fluid comes out. Pins 1,2,5 all measure ~ 2 ohms to ground. There is a buzzing sound and the pedal vibrates with the 12V and pushing the brake pedal. I have owned my M3 since new and it only 51K. The ABS unit looks like new as does the entire car. Does anyone have any suggestions? Do I need a $1800 rebuild for my Bosch 0 265 200 042?

[MrBurgundy]

is the pedal hard or soft?

Those master cylinder reservoirs are partitioned so make sure the fluid is topped off enough to spill over the wall inside the tank

Also check to see if the rubber lines in the rear are rotted and collapsed.

crack the rubber hose at the caliper and step on the brake. If you got no fluid still crack it at the metal line before the rubber and see if fluid starts to flow then.

[ehrawn]

When you depress the pedal, how far back are you getting fluid pressure? It’s possible that the lines might be occluded or that there might be a leak before the fluid reaches the rear calipers. Start breaking connections one at a time between the caliper to the master cylinder (from the rear to the front) to isolate the location of the problem.

[FredK]

I agree with the previous posters to systematically check the hydraulics from rear to front. You mention that you have owned the car since new -- have you ever changed the rear brake soft lines? Over a very long time, they can swell internally and become occluded. Thankfully, they are inexpensive and not terribly difficult to replace. There are two brake soft lines per side of the car, one from on top of the subframe to the trailing arm, and one that connects from the hardline mounted on the trailing arm to the caliper.

[82eye]

sounds like the screens in the abs unit plugged.

[e30m3s54turbo]

I had problems on my m3. The fronts were not bleeding correctly. I pulled the abs of and lines. It turned out to be a clogged line.