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Discussion Starter · #1 ·
Hi Everyone, I'm relatively new to this forum, I've tried to search the forum on this topic but have had no luck. I'll try to be complete and concise on the issue and will appreciate any feedback...thx

My son recently acquired a 1992 5-speed 525i with 105K miles on it. It's relatively clean and seemed to be well maintained. The tires needed replacing so I took the car to our local Mavis dealer and bought a new set of tires (Firestone AS). On the drive back I wanted to test out th brakes of the car since he'll be driving it. Under hard braking the car pulled hard to the right. I figured it was a frozen driver side front caliper. I was planning on doing a full break job, now I was going to rebuild the calipers as well. Before I started I tested the front caliper theory by jacking the front end of the car, having him press the break pedal as I tried to spin the front tires. As I suspected, the passenger side front wouldn't turn but the driver side front tire would spin no matter how hard he pressed the brake pedal.

I replaced all the rotors, pads, sensors, rubber break lines and started to bleed each caliper starting with the left rear, right rear, front right and finally the front left. I forgot to mention that when I emptied the break fluid reservoir, there was a reasonable amount of "gunk" at the bottom of the reservoir, rust color. I found the same substance in all the caliper, especially the from when I was changing the seals.

Everything was going great until I tried bleeding the right front caliper (the one that I thought was originally frozen), no fluid would come out. The new hose was fine so I thought the hard break line going from the ABS unit to the new hose was clogged. I removed the line and I was fine.

Which leave me with the potential problem of having a clog in the ABS unit. I removed the unit and starting testing the various ports with compressed air. All the ports work fine with the exception of the front left port. zero air comes out of the circle port when you are pushing air thru the port the master cylinder connects to, the right and rear port works fine, and that's why they could all be bled.

I'm pretty sure you can't service ABS unit. I thought it was purely passive but maybe something is clogging that line. Any thought?



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