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Thread: E36 ABS Actuator - Rebuild Options?

  1. #1
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    E36 ABS Actuator - Rebuild Options?

    I recently diagnosed a faulty ABS hydraulic pump/actuator in my '99 M3 race car as the cause of an ABS problem that only manifested itself on track. I bought an actuator off a wrecked car that was known to have a working ABS at the time of the wreck.

    I was surprised to learn that BMW no longer makes these ABS hydraulic actuators and apparently no 3rd party manufacturers have picked up the supply of new replacement units. Given the large number E36 cars manufactured and the reality that any parts scavenged off junk cars are pretty old at this point, I was wondering if anyone knows of a source for rebuilding these units with new parts.

  2. #2
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    If your rules allow it, look into putting in an E46 MK60 system.
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  3. #3
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    Quote Originally Posted by fbirch View Post
    I recently diagnosed a faulty ABS hydraulic pump/actuator in my '99 M3 race car as the cause of an ABS problem that only manifested itself on track. I bought an actuator off a wrecked car that was known to have a working ABS at the time of the wreck.

    I was surprised to learn that BMW no longer makes these ABS hydraulic actuators and apparently no 3rd party manufacturers have picked up the supply of new replacement units. Given the large number E36 cars manufactured and the reality that any parts scavenged off junk cars are pretty old at this point, I was wondering if anyone knows of a source for rebuilding these units with new parts.
    FYI, it's almost always "just" the wiring. There's a ribbon cable and/or solder joints that get flaky. If you're decent with a soldering iron, it's a 1 hour fix. Pop the back off (about 5 torx bolts) and have a look. I'd do it to any used one before I installed into the car. Use quality wire with quality insulation. Those solenoids can draw ~3.5 amps.
    I think we see this failure on track/race cars a lot because we're banging those solenoids a LOT more than on the street. Hence, those ribbon cables get pretty toasty.
    Last edited by aeronaut; 04-22-2018 at 09:34 PM.

  4. #4
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    Quote Originally Posted by aeronaut View Post
    FYI, it's almost always "just" the wiring. There's a ribbon cable and/or solder joints that get flaky. If you're decent with a soldering iron, it's a 1 hour fix. Pop the back off (about 5 torx bolts) and have a look. I'd do it to any used one before I installed into the car. Use quality wire with quality insulation. Those solenoids can draw ~3.5 amps.
    I think we see this failure on track/race cars a lot because we're banging those solenoids a LOT more than on the street. Hence, those ribbon cables get pretty toasty.
    I've yet to open the original unit, but I suspect the problem is a faulty solenoid. The ABS would work fine for the first 3-4 laps of the first track session of the day and then the front right wheel would start to lock. After the first session of the day the same wheel would lock after 1-2 laps. Seems as if one of the two the solenoids controlling that wheel was getting hot and failing after a few activation cycles. I suppose a weak solder joint could also overheat with activation cycles, but I'm more suspicious that a moving part (i.e., solenoid) will deteriorate with age and use.

    - - - Updated - - -

    Quote Originally Posted by gobuffs View Post
    If your rules allow it, look into putting in an E46 MK60 system.
    My rues allow it and eventually I'll go that route. But $50 for a replacement E36 pump/actuator was lot cheaper and quicker.
    Last edited by fbirch; 04-22-2018 at 10:08 PM.

  5. #5
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    Very easy to pop the back off and test the solonoids. My bet is they're fine.

  6. #6
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    Took the plastic case off the solenoid bank and inspected the wiring with a magnifying glass and ohmmeter. Can't see any flaws in the solder joints, no evidence of wire burning or overheating, no frayed insulation jackets, etc. The impedances are correct from the input connector all the way to the leads on the solenoids (essentially zero ohms). I even wiggled all the wire bundles from the input connector to the ribbon cables inside the solenoid bank and continuity was rock solid. The winding impedances of the solenoids were also consistent within family, but the output solenoids have different impedance from the input solenoids. Tomorrow I'll have access to a big power supply and will try cycling both the input and output solenoids for the wheel that locked up with this ABS pump unit. It'll be interesting to see if I can make it fail on a test bench with repeated activations.
    Last edited by fbirch; 04-24-2018 at 10:16 PM.

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    Interesting Felix. Keep it up.


  8. #8
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    If you're interested, I have a 4-channel ('96-'99) E36 M3 pump assembly I would sell. I removed it from a car I parted out and my racecar uses a 3-channel ABS system so I cannot utilize it as a spare. If you're interested, send me a PM.
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  9. #9
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    And I can offer the opposite. I have a spare 3-channel pump (off a '94 325is) I pulled from my wrecked (in the rear) track car but my new racecar is 4-channel so it's not compatible.

  10. #10
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    Quote Originally Posted by zabuomar View Post
    If you're interested, I have a 4-channel ('96-'99) E36 M3 pump assembly I would sell. I removed it from a car I parted out and my racecar uses a 3-channel ABS system so I cannot utilize it as a spare. If you're interested, send me a PM.
    PM sent

  11. #11
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    I tried repeatedly actuating the two solenoids that control the wheel where I consistently got lockup with the old actuator. Unfortunately the output voltage of the power supply I was using would sag to 6-8 volts when loading it with the solenoid winding. Consequently, the current through the solenoid was also lower than normal. Even so, I could hear the solenoids making a mechanical noise, so I believe they were activating. I couldn't get either one to freeze up after a few minutes of cycling, but I also wasn't driving them with full current or voltage. My test is therefore inconclusive. I may try again with a more robust voltage source but for now will just run the replacement actuator to see if it solves my problem long term.

  12. #12
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    FYI, on my 95 ABS pump, there are two solonoid types, stamped 5018 and 5019. 5018's draw 3.5A, 5019's draw 2A.

  13. #13
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    Quote Originally Posted by aeronaut View Post
    FYI, on my 95 ABS pump, there are two solonoid types, stamped 5018 and 5019. 5018's draw 3.5A, 5019's draw 2A.
    Yep, that roughly corresponds with the winding resistance I measured on my '99. The input solenoids have about 7.2 Ohms winding resistance and the output solenoids have about 3.5 Ohms. At 3.5+ Amps, I'd expect those coils to get hot with the repeated activation cycles that happen on track, but BMW built a very robust assembly.

  14. #14
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    Hi All,

    I'm having the same issue with the ABS pump disengaging intermittently. ABS often fails (ABS light turns on) after several runs in auto-x when I experience front wheels locking up - seems to be heat related? However, my ABS also fails by just after starting the car up (cold) and slightly rolling over a bump causing a jerk, then the light comes on.

    It almost never resets, when I turn the car on and off immediately. But it resets sometimes after 15 min to 1/2 hour to an hour.

    What I've done so far to diagnose...
    I've got a reader that stated a code of "145 - Pump/Pump Relay" issue and nothing else. I've replaced both the ABS and ASC relays and the symptom has recurred, so we can rule out the relays as the issue. So what I'm left with is the Pump per the code reading...
    I can say that the pump can't be completely dead as it's only intermittent and failing "sometimes". I can definitely feel the ABS in auto-x runs when I brake hard enough to make it pump...but then it fails sometimes almost consistently on my last runs.

    Would appreciate if there's any updates or suggestions before I start looking for the another used used pump since they don't make them anymore. UGH! and they're not cheap.

    Thanks!

  15. #15
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    Projecte36,

    Most likely the thin wiring filament INSIDE the pump has deteriorated and is starting to short during certain maneuvers or temps. You can find a few DIY's on this forum that show how to re-wire the pump by taking the bolts off of the backing plate and using regular automotive wire to join the terminals.

  16. #16
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    Quote Originally Posted by olemiss540 View Post
    Projecte36,

    Most likely the thin wiring filament INSIDE the pump has deteriorated and is starting to short during certain maneuvers or temps. You can find a few DIY's on this forum that show how to re-wire the pump by taking the bolts off of the backing plate and using regular automotive wire to join the terminals.
    This. Very likely. Classic symptoms of that problem. I used 'Radiation-Resistant Wire' ordered from McMaster Carr. It has a high temperature rated insulation, so small gauge can handle large current, eg 22gauge can handle 14A. Those solenoids in the ABS pump can draw 3.5A, and 2 can be on at the same time. Some of those wires are shared.

  17. #17
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    Quote Originally Posted by aeronaut View Post
    This. Very likely. Classic symptoms of that problem. I used 'Radiation-Resistant Wire' ordered from McMaster Carr. It has a high temperature rated insulation, so small gauge can handle large current, eg 22gauge can handle 14A. Those solenoids in the ABS pump can draw 3.5A, and 2 can be on at the same time. Some of those wires are shared.
    Thank you for the quick responses, aeronaut and olemiss540!!! Greatly appreciate the insights! Will give it a shot.
    Love this forum!

  18. #18
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    Quote Originally Posted by Projecte36m3 View Post
    Hi All,

    I'm having the same issue with the ABS pump disengaging intermittently. ABS often fails (ABS light turns on) after several runs in auto-x when I experience front wheels locking up - seems to be heat related? However, my ABS also fails by just after starting the car up (cold) and slightly rolling over a bump causing a jerk, then the light comes on.

    It almost never resets, when I turn the car on and off immediately. But it resets sometimes after 15 min to 1/2 hour to an hour.

    What I've done so far to diagnose...
    I've got a reader that stated a code of "145 - Pump/Pump Relay" issue and nothing else. I've replaced both the ABS and ASC relays and the symptom has recurred, so we can rule out the relays as the issue. So what I'm left with is the Pump per the code reading...
    I can say that the pump can't be completely dead as it's only intermittent and failing "sometimes". I can definitely feel the ABS in auto-x runs when I brake hard enough to make it pump...but then it fails sometimes almost consistently on my last runs.

    Would appreciate if there's any updates or suggestions before I start looking for the another used used pump since they don't make them anymore. UGH! and they're not cheap.

    Thanks!

    How’d this eventually net out? Having same abs issues , and identical intermittent cold start over bump and back on dash :/ Replaced all but the control unit and the hydro unit.

    Guess worth pulling and checking the ribbon wires. Has there been any revelations to that fix since this thread ?

  19. #19
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    No relevations I am aware of. Any e36 pump I run I rewire to eliminate this known failure. It is basically free and takes about 2 hours with a solder iron.

    Then the system will ultimately fail for other reasons and since it is so hard to diagnose I end up running an mk60 or without ABS:-)
    Last edited by olemiss540; 07-19-2023 at 11:02 AM.

  20. #20
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    Quote Originally Posted by olemiss540 View Post
    No relevations I am aware of. Any e36 pump I run I rewire to eliminate this known failure. It is basically free and takes about 2 hours with a solder iron.

    Then the system will ultimately fail for other reasons and since it is so hard to diagnose I end up running an mk60 or without ABS:-)
    I had this wiring problem on 2 out of 3 pumps. And yep, the E36 original ABS systems are finicky. Years ago I gave up on one and took it to the dealer and paid +$200 to be told they couldn't find the problem and was given a print out that gave the order in which to replace all the parts.

  21. #21
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    Quote Originally Posted by olemiss540 View Post
    No relevations I am aware of. Any e36 pump I run I rewire to eliminate this known failure. It is basically free and takes about 2 hours with a solder iron.

    Then the system will ultimately fail for other reasons and since it is so hard to diagnose I end up running an mk60 or without ABS:-)
    Bummer. I’ll be pulling mine to get started on rewire. Are you using mk60 as standalone? No abs sucks. And potentially expensive flatspotting



    Quote Originally Posted by aeronaut View Post
    I had this wiring problem on 2 out of 3 pumps. And yep, the E36 original ABS systems are finicky. Years ago I gave up on one and took it to the dealer and paid +$200 to be told they couldn't find the problem and was given a print out that gave the order in which to replace all the parts.
    Was a pinch close to making a quick dealer trip for pinpoint confirmation, except it’s triple digits- so car doesn’t see sunlight lol. How have they been holding up long term ?


    Sent from my iPhone using Tapatalk

  22. #22
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    for those that rewire the module, did you actually desolder the crusty ribbon connector or did you end up ripping it off? Mine is corroded but I won't want to risk a fire trying to desolder it.

  23. #23
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    "just ripping it off" would create a mess. You'll want to desolder, and may need to wick away excess old solder. I'd also at least use tefzal wire, or a wire with even higher temperature insulation / current rating.

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