ABS questions for E34 drivers front brake not working

[Christ Is Lord]

This is my son's account and car, this is dad asking the question. My son bought the 1990 BMW 525i for a case of Guinness. It had not run since 2020. I have worked on cars that have sat for years since the 70's. My son got it running now, but we are having a problem with the drivers side front brake and I wanted to ask some of the folks that understand or have repaired the ABS unit. I saw a chat from 2019 on the bimmerforum chat bringing us to your forum.

We are fixing the car’s clutch master cylinder and want to get it driveable soon. At this time I do not want to disconnect any brake lines because the 3 of 4 brakes are working fine and are bleedable. Jamming the brake with the driver's side front bleed valve open did nothing. Jamming the pedal with max force does not clamp the drivers side caliper when not bleeding. The caliper is full of fluid as a micro amount dripped out when the bleed valve was first opened. The system fluid is typical and not real dirty.

I am reading about running the ABS pump to try to reset the ABS valves. We would rather turn off the ABS or bypass it until the young son can pay for tires and other things it needs.

Questions:
1. Will running the ABS help and does it run for all brakes at once, or can it be run for the specific wheel? It would be awesome to know which pins to power and any technique; we have the Bentley manual.

2. Can coordinated pounding the caliper piston in, to force the fluid to pop the stuck valve in the ABS unit be a trick to fix for this? Tapping on the fuel pump got it working, does tapping on the abs help? (which direction?)

3. Any bypass kits available or any other tricks up someone’s sleeves?!?

Thanks for some ABS assistance!, Future BMW driver’s Dad

[gadget73]

Before you get too deep into ABS stuff, are you certain its not just a collapsed rubber hose? Since nothing comes out of the bleeder, try cracking the hard line where it goes into the rubber hose and see if you get fluid there. If it bleeds on one side but not on the other, replace the hose and I'd do it's twin on the other side.

[Christ Is Lord]

Yeah I ended up replacing the ABS unit from pull and part for $83, that was not the fix I should have checked here sooner but I have eventually replaced the two rubber hoses and that was the fix.

Thanks,

P.S. this is the account owner not my dad who posted the question.