Brake Problem, Stumped.

[yamsandclams]

A few days ago I noticed that my front drivers side caliper was not engaging. Im not sure what caused that as it was kind of sudden, however, I took I saw it as an opportunity to rebuild the calipers and change the brake fluid hoses. When I went to bleed the brakes, I used a motive power bleeder. I was able to bleed the other 3 calipers just fine, however, I am unable to get fluid to the front driver side caliper. I tried to bleed manually way with a helper as well, and I am noticing that the brake fluid level is not dropping.

The realoem diagram for the brake plumbing is not clear to me, however, I am being led to the conclusion that the issue may lie with the ABS module or the master cylinder. However, I am not so certain about the master cylinder as I was able to bleed the other 3 calipers. To add to the confusion, I'm not certain its a clog either as my understanding is that the only part that could get clogged is the rubber hose (which I replaced) and the rest of the system upstream is composed of metal brake pipes.

I'm not exactly sure how to proceed with troubleshooting at this point. Any advice or should I just start replacing the mentioned parts (MC, ABS module) ? I tried researching other posts on the forum but I feel like I got stuck in a logic loop. pls help.

[StephenVA]

You have a classic ABS port locked down.

You need to activate the bleeding procedure with a scanner (Try buying a Foxwell 510 unit). It will cycle the ABS unit as you move through the procedure of RR, LR, RF, LF. The proper process is pressurize the master at 20 PSI, bleed until fresh fluid is seen at caliper.
- activate the ABS bleed procedure leave open the caliper bleed screw while it cycles, then apply three pedal pumps with the bleeder screw open, close bleeder screw and move to the next caliper. Each caliper may take a while to clear all the air from the ABS block as it has to travel all the way through the line to the respective caliper. I personally do each caliper three times. Then I am anal.....
Plan on three Qts of fluid.

[geargrinder]

Yeah - I'd add - have you been either driving around with DSC & brake lights on in the cluster, or, has somebody snipped out the cluster lights? That kind of problem should absolutely have thrown a code by now and been warning you on the dash. Definitely scan the ABS/DSC module (by the way - you don't say what car you have... thats actually helpful very often... I'm presuming this is not the Mini...)

[yamsandclams]

You have a classic ABS port locked down.

You need to activate the bleeding procedure with a scanner (Try buying a Foxwell 510 unit). It will cycle the ABS unit as you move through the procedure of RR, LR, RF, LF. The proper process is pressurize the master at 20 PSI, bleed until fresh fluid is seen at caliper.
- activate the ABS bleed procedure leave open the caliper bleed screw while it cycles, then apply three pedal pumps with the bleeder screw open, close bleeder screw and move to the next caliper. Each caliper may take a while to clear all the air from the ABS block as it has to travel all the way through the line to the respective caliper. I personally do each caliper three times. Then I am anal.....
Plan on three Qts of fluid.

I will try this. Thank you.

Yeah - I'd add - have you been either driving around with DSC & brake lights on in the cluster, or, has somebody snipped out the cluster lights? That kind of problem should absolutely have thrown a code by now and been warning you on the dash. Definitely scan the ABS/DSC module (by the way - you don't say what car you have... thats actually helpful very often... I'm presuming this is not the Mini...)

It is an '01 540i. Well, I can confirm power to the dash lights. The ABS, DSC, and BRAKE lights light up when ignition is turned on, but turn off when the engine is running. I tried to bleed per some other forum advice with the abs module unplugged and got the trifecta lights, but that went away when I plugged the module back in. I will check the ABS and DSC modules as well. I ordered a cable to try the above advice, I'm now waiting for it to arrive.

[rdl]

I'd discount a master cylinder problem - right front bled OK and both front brakes are activated by a common pipe from the master cylinder.

You didn't mention, but I assume the pedal didn't sink when you tried traditional "down down, up up" bleeding with a helper. If it did sink we'd need to figure out where the fluid is going. Anyway assuming it didn't ...

From MY 2000 forward all E39s have the DSC III Bosch 5.7 version of ABS/DSC. This image should help explain the brake line routing

Attachment 640909

EDIT: Oops, I get an invalid attachment. let's try that image again
Attachment 640909

EDIT2: I don't know why it isn't working here. See next post #6 for the image.
This image shows all valves in their normal, rest, position, i.e. nothing activated with the brakes acting in fail safe non ABS mode.

Since bleeding with the ABS/DSC unplugged didn't solve the problem one has to assume the logic board is exonerated.

I'd first try "bleeding" with the brake line loosened or disconnected at the ABS/DSC block to eliminate the possibility of a line blockage. This image should help. Even though the page is for my 530, all the Bosch 5.7s are supposed to be the same.
DSC57_LineConnectionsAtModule.jpg
The translator messed up on this page - the labels don't match with the legend. But HECK in German means rear & VOR means front. So I make the front left pipe to be VL in the image. Ignore the number labels, it's a generic/recycled image and the numbers apply to other instructions. If no "bleed" at the ABS hydraulic block with a loose connection, it seems to me that leaves two possibilities. Either one of the two valves for that corner (most likely the inlet) is stuck in its activated position, or one of the solenoids is jammed and holding a valve in the activated position - again most likely the inlet.

I'd try removing the electronic module, which contains the solenoids, from the hydraulic block (just as folks sending the module out for repair do while driving the car pending the module's return) and try bleeding again. If success, one of the two solenoids is faulty and the module needs repair. You'd have to ask vendors if that is possible. I've only ever read of circuit board repairs, never any mention of solenoids, but certainly worth the questions.

If no success with module out, one of that corner's two valves in the hydraulic block is faulty. If it's the hydraulic block I'd recommend a replacement unless you could find someone to guarantee a repair. Even it could be joggled loose back into position with the DIS bleed cycle I wouldn't have any faith that it wouldn't jam again some time. And Murphy's Law says that is likely to be at the worst possible moment.

[rdl]

Try again for the hydraulic plumbing image

DSC5_7_HydraulicUnit.jpg

[pshovest]

I believe there are two flex hoses per caliper. The second one is behind the ABS pump. Crack open the connector while applying brake pedal pressure.

[yamsandclams]

Try again for the hydraulic plumbing image

DSC5_7_HydraulicUnit.jpg

Replaced the hydraulic unit and bled with INPA. Brakes are now working normally. This diagram saved my life. Thank you for your help.

[rdl]

Thanks for reporting back with results - so many don't & everyone is left wondering at the result. And this one was worth knowing - it's the first instance of a hydraulic block failure that I can recall.

[JimLev]

RDL, thanks for the drawing. Don't think I've ever seen that one before.

[geargrinder]

Agree on both of the above posts.

[rdl]

RDL, thanks for the drawing. Don't think I've ever seen that one before.

The image was found in the attached DSC documents, along with some details of DSC operation.

I have two other PDFs on the same topic:
bmw_e46_bosch_dsc_iii_5p7_training_manual[1]
bmw_e46_traction_and_stability_control_training_ma nual[1]
But each are more than 1 MB, above the forum size limit, at 1.3 MB & 3.3 MB respectively. And none of the compression methods I have will reduce them under the limit. If anyone is really interested I'll look for a way to break them up into pieces. Anyone with suggestions on how to do that?