Today was the day that I was going to completely finish off the E30 project; apparently the car has other plans. I've owned very few cars equipped with ABS so I'm a bit stumped.
1987 BMW 325i, 101k miles, new front calipers and lines. 4 wheel disc brakes. Ran and drove without ABS warning lamp.
Diagnostics so far:
- No fluid to rear brakes. Brake line from ABS pump clear. Discovered there was no fluid leaving the ABS pump to the rear lines. (Tried with car running as well and no change.)
- Good flow in both lines from the master cylinder to ABS pump
- Front brakes bleed normally
From what I've read in the service manuals, the ABS pump should let fluid pass through without a need to cycle the pump as in later models. I will try manually activating it but am skeptical of the result. Is there any course of action besides replacing the pump with a used one? I hate the idea of replacing a nice clean 100k pump with a 200k+ unknown junkyard unit.
Picture of offender:
It sounds like thw hold valve is stuck.
Have you tried percussive agitation?
Knurled. said:
Have you tried percussive agitation?
Haha that's a great way to put it...I'll give it a go. Reminds me of how we never say "it blew up" at work...it's either a thermal event or an unscheduled disassembly.
Sometimes the ABS hydraulic assembly can be damaged by crud getting pushed upstream when caliper Pistons are pushed in for pad changes. We recommend opening caliper bleed screw before pushing piston, so the cruddy old fluid goes out the bleeder instead of upstream through the ABS hydraulic assembly.
beyond that, I got nothing.
Robbie
PowerDork
2/17/18 10:21 p.m.
Had this happen on a similar vintage 750il.
Pull the relay cover, manually jumper the abs relay to cycle the solenoids, tap three times with hammer for luck, check again.
Worked for me.
In reply to AngryCorvair :
Yeah I generally do that with pad changes but in this case I removed both calipers and rebuilt them on the bench so no fluid was forced back through the ABS assembly. Could be that it is gummed up from sitting around for years.
In reply to Robbie :
I'll try that and see what happens.
Good news! A few rounds of manually cycling the pump and some love taps with a hammer and the ABS unit seems to be working again. My wife hopped in the car and the rear brakes once again had fluid. Lots of dirty crusty looking fluid, but fluid nonetheless!
Thanks for your help guys
After you have all clean fluid in there, I would go find a gravel road and cycle the heck out of the abs, then bleed a bunch through again. It will either clear itself completely, or lock up again and you will know you need parts.
It's entirely possible, if it was driven by a gentle driver the abs pump hasn't run since the car was new.
In reply to enginenerd :
I got a same problem with my Hyundai unit now. Been bled and no fluid is coming out of the system. I would like to try this but I don't know where to tap the hammer. Can I know specifics on the job you did? Would help me very much. Thanks!
In reply to LuckyTucson :
I just gave the ABS pump (not the module w/ the sensitive electronics) a few light taps with a small hammer. I'm not sure if it was that or manually powering the solenoids that freed things up.
