Cycling ABS Solenoid Valves - Need help

[Boise]

Long story short, I rebuilt my brake calipers this winter and I managed to get air in the ABS unit. I need to cycle the unit to remove the air so I can bleed it out. I have tired actuating the ABS unit the normal way, i.e., stopping hard. But with a combination of sticky tires, warm weather, and sub-par braking dues to air bubbles I have been unable to activate the ABS. I have heard I can take it to the dealership and they are able to cycle it, but I don't like the dealership, they are jerks and they charge and arm and a leg.

So I did some research and found this on s14.net.

http://www.s14.net/forums/showthread.php?15736-help-needed-with-brake-problem/page3&highlight=cycle+abs+pump

They have this nice electrical diagram of the ABS system posted. I cant find anything in the Bentley manual on the ABS electrical


Following the instructions there, I have been able to get the ABS pump to turn on by jumping the 87 and 30 pins of the relay on the left (see the green line in the picture below), but I do not know how to cycle the solenoid valves.


I need to jump the 87 and 30 pins on the relay on the right (Blue line) which does nothing on its own. I think I also need to jump pins 1, 3 and 5 (individually) to actuate the three valves. I am not sure which wires I need to jump. I assume the wire are in the box I circled in yellow. Any ideas as to which pins I need to jump? According to the diagram, pin 1 is a brown/red wire, which I don't see. I see a brown/black and a brown/white for pins 3 and 5. Do I just jump those to the ground?

Thanks for your help.

[Chuck C]

Your best course of action is to find an independent shop with a GT1 or Autologic diagnostic tool, and let them run through the bleeding procedure. You can jump those pins to ground while a pressure bleeder is hooked up, and you might get all the air out, or you might fry the ABS control unit. Pin 1 is the upper RH one, in your picture.

[dirty thirty]

having the same issue any luck?

[jlevie]

To cycle the ABS unit pin 2 & 11 at the ABS unit or pins 27 & 28 at the ABS module need to be grounded when the ignition is on. On later BMW's you can use a GT1 or DIS to put the ABS into bleed mode, but not on an E30.

[Boise]

having the same issue any luck?

Update, I did this a few weeks ago and here were the results.

I have been able to get the ABS pump to turn on by jumping the 87 and 30 pins of the relay on the left (see the green line in the picture below). The pump turns on and makes noise. I then jumped the 87 and 30 pins on the relay on the right (Blue line) and jumped from the ground 87a on the right relay (red circle) to each of the wires numbered 1 through 3 in the yellow box. I can hear a click when jumped those wires, so I assume that was the valve actuating. When I turned the car on I had the ABS light on, but an unplug of the car battery fixed that and it has not come on again, so I don't think I fired anything.

I re-bled the brakes, but unfortunately they are no better. I rebuild the calipers and did new pads an rotors, so maybe its something with that resulting in my problems. I don't think I glazed the pads, but who knows.

[cheapthrills]

with a combination of sticky tires, warm weather, and sub-par braking dues to air bubbles I have been unable to activate the ABS.

Have you tried stomping the brakes on a dirt road? A potholed road should work as well.

Are you sure the system worked beforehand?

How is your master cylinder?

[Cloudbase]

To cycle the ABS unit pin 2 & 11 at the ABS unit or pins 27 & 28 at the ABS module need to be grounded when the ignition is on. On later BMW's you can use a GT1 or DIS to put the ABS into bleed mode, but not on an E30.

Jim, I'm pretty certain I have a little air in my ABS system. I've had a soft pedal for years that will not go away after new soft lines, rebuilt calipers, a brand new master cylinder, and a ton of pressure and manual bleeds by me and well respected Indy mechanic.

When you say its possible to activate the abs by grounding (not jumping?) pins 27 & 28 at the abs modules do you mean the control unit (under the dash)? I don't want to blow the internal fuse in the control relay. I haven't pulled my cruise control to look under the cover of the abs unit yet, maybe I'll understand once I get in there. I have a fused and switched jumper I can use.

[vpilarrt]

When you say its possible to activate the abs by grounding (not jumping?) pins 27 & 28 at the abs modules do you mean the control unit (under the dash)?

Yes, ground pins 27 and 28 on the control module located under the dash on the driver's side. This turns on the pump motor and opens the solenoids.

[Cloudbase]

Thanks. Do you know what pin in the module is ground? Or do you just ground to a good source under the dash. I don't have it in front of me, but I'm assuming you mean the pins in the wire harness that connects to the control module, not cracking open the module.

[nando]

what pads do you have?

I had a similar issue. I couldn't activate ABS even if I stood on the pedal, even on snow tires in the rain. pedal was mushy - and the brakes were a little scary (my wife refused to drive it). I knew it wasn't right as the brakes were fantastic before.

I replaced the MC, replaced the lines, replaced the calipers, bled it, replaced pads/rotors (my second set of Hawk HPS), etc. Then I ditched the Hawk HPS pads for some stock pads (pagid) because that's what I'd used before and I knew it worked. Wow. Pedal was back to the way it should be, suddenly I can activate ABS again, no more scary brakes. Hey they even work well when they're cold! it was an eye opener for sure.

Now I lump Hawk HPS into the same category as Yokohama ES100s and $30 HID kits.

Another thing about bleeding the brakes, I use a pressure bleeder which helps, but you can still have air trapped in there. use a large wrench or ball peen hammer and tap on the calipers as you bleed them. you can also tap on the ABS body. I usually get a few more small bubbles out that way.

[Cloudbase]

I just installed HPS with Mazda RX-7 calipers, but had Pagids on stock rebuilt calipers for years. Every component except the hard lines, proportioning valve, booster, and ABS system has been rebuilt or replaced with new parts (MC - girling to match the girling booster).

My ABS has always functioned correctly and other than my persistant soft pedal my brakes are great.

The reason I suspect the air in the ABS over some type if line leak is that I have literally gone years without touching the system and lost no fluid.

I've pressure bled it, manully bled it, pressure and manually bled it. Tapped on the calipers, pumped the pedal 12 times (per the Bentely), bled it - driven it - bled it - driven it. Nothing works.

With the car off and no vacuum boost the pedal will slowly sink to between half way or all the way to the floor over a period of 20 - 30 seconds.

[Artful Dodger]

I didnt see this exact wording in your posts. I think that you need to bleed the brakes while the ABS unit is jumped out. this would give you the ability to push fluid into the unit and expel any air.

did any of you do this?

I am curious, i am about to start to repair my brakes.

[nando]

I've never done that. never had to.

also, when the ABS pump is running, it closes the valves to the different lines - it doesn't open them. by default they are all open.

[Cloudbase]

Short of replacing hard lines (which I don't think are leaking due to the lack of fluid loss over time), I'm at my whits end. Running the ABS while bleeding might at least eliminate that from the list.

[vpilarrt]

also, when the ABS pump is running, it closes the valves to the different lines - it doesn't open them. by default they are all open.

Yeah, you're right. Also, I've never had to mess with the ABS Pump when I was bleeding my brakes. I think the OP has a different issue.