My Brake Pedal Feel is Kicking My Butt... - Page 4 - BMW M5 Forum and M6 Forums
E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #31 of 201 Old 16th December 2018, 05:52 AM
herrubermensch
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Originally Posted by xrviz View Post
My guess is if you compared OPs pedal with your car's pedal with engines off you would feel a difference. Then with engines on your pedal is easier and his goes to the floor.
Very well could be, and that would explain it.

--Peter
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post #32 of 201 Old 16th December 2018, 07:58 AM
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Originally Posted by mr_g_bock View Post
Still a crazy situation...





I was able to use ISTA+ to work all of the ABS valves and pumps. I don't think there is an issue with it, also since it is a separate closed system when not activated, it should have no effect on normal braking conditions.


When I next test, I will pull the DSC & ABS fuses to remove that from the equation.


I normally avoid brake threads because they are confusing. Sorry I have not read the whole tread just jumped into the most recent replies, apologies if I missed something important.
Have you considered that you have a hydraulic leak in the solenoid pack of your ABS unit? When the car is off only a very small amount of fluid leaks because you can't apply enough pressure to have enough fluid "float" the pintle in the solenoid. When you add the power of the booster there is enough flow of fluid to "float" the pintle up and allow for faster escape. There is no way you can test that, you need to remove the lines from the ABS unit and put either by pass lines on or pressure gauges, usually a combo of both.
The only way without spending hundreds on equipment is blindly replace the hydraulic part of the unit or take it to someone with the equipment. If you actually had a leaking caliper you would see the signs, lift a boot seal and see if there is fluid but if after one or two pumps there would be enough fluid to make your boot look like a water balloon. Trust me you would have noticed.



Unplugging the main cord of the ABS unit or fuses will tell you if you have a fault in the electric side of the ABS unit that opens a solenoid but it will do nothing for a solenoid that has a hair in it or part of the filter lodged in it. They can also just corrode if garage queens, water in the fluid will collect at the noids.
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post #33 of 201 Old 17th December 2018, 05:43 PM Thread Starter
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Thanks Sailor24,



My problem may just well be in the ABS unit. I will check to see if there is a shop in the Orlando metro area who can diagnose & fix ABS unit.


I am still waiting for caliper rebuild parts to arrive and will rebuild them anyway.


Modern cars have become way too complicated...
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post #34 of 201 Old 20th December 2018, 12:49 AM Thread Starter
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My parts are starting to arrive...


I found a posting on how to check the wheel speed sensors (diodes) and will do that shortly. The post also talked about re-soldering the ten terminals that bridge the DSC/ABS module to the hydraulic module. I will look at my terminals and see if I should do this too. Once done, I will use ISTA+ to cycle the pumps and valves to make sure that is working.


I will also do another 'in car' master cylinder bleed. I am thinking of plugging two of the MC ports and only run one hose to the reservoir and pump, then move the hose to another port, plugging the latter and pump, and again for the third port. Not sure if this makes any difference as opposed to running a hose from all three ports at once. I would like to know for sure the the MC is bled completely!!!


Hope to do all this before the Holidays get busy!!!


Happy Holidays to all!!!!!
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post #35 of 201 Old 21st December 2018, 02:06 AM
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Glad I found this thread, as I'm experiencing VERY similar issues with the 2000 M5 that I just bought this week with a long, soft pedal, no improvement with bleeding, but also no warning lights. A question for you though, perhaps the strangest symptom that I'm experiencing is that the pedal is actually very firm and difficult to push while I'm trying to bleed the brakes, even with the caliper nipple open! Happily though, I actually have an extra ABS unit, albeit with a bad controller, but I'm just going to pull the hydraulic unit off the back of it and try swapping that out tomorrow to see if it improves matters.
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post #36 of 201 Old 21st December 2018, 06:02 AM
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Quote:
Originally Posted by mr_g_bock View Post
I found a posting on how to check the wheel speed sensors (diodes) and will do that shortly. The post also talked about re-soldering the ten terminals that bridge the DSC/ABS module to the hydraulic module.
What ten terminals? Inside the electrical half? I don't recommend that. You are referring to the Bimmerfest thread? Only one guy of all who attempted that had success and even he had to redo it. Some of the wires inside are like 30 AWG. Aka angel hairs. Been there done that, got the headache. If you don't have ABS/DSC codes you should not open the module.

My .02.

Good luck sorting this out, seems like a common issue.
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post #37 of 201 Old 21st December 2018, 07:03 PM
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Originally Posted by xrviz View Post
What ten terminals? Inside the electrical half? I don't recommend that. You are referring to the Bimmerfest thread? Only one guy of all who attempted that had success and even he had to redo it. Some of the wires inside are like 30 AWG. Aka angel hairs. Been there done that, got the headache. If you don't have ABS/DSC codes you should not open the module.

My .02.

Good luck sorting this out, seems like a common issue.
There is an old thread here where one of our members did a repair. See I this is helpful.

https://www.m5board.com/vbulletin/e3...terminals.html

Regards,
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post #38 of 201 Old 21st December 2018, 09:15 PM Thread Starter
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gsfent, xrviz,


Maybe I won't open the ABS/DSC unit to avoid adding headaches to this situation that is driving me nuts!!!


I wish I still had my 1964-1/2 first year Mustang!!!! Keep it simple, easy to work on and repair!!!!


Earlier today I tried to test the wheel speed sensors (the diode in each), but my multi-meter did not show any readout even when I reversed the meter probes. I tried this at the ABS/DSC connector and the sensor connector (did FR and RR sensors). I would like to know how to confirm that the meter is working and if I have to do something at the sensor. There are pictures in the Old Terminal post that just shows the probes touching the two sensor terminals. And I did have good batteries and meter set to diode setting, but I only see a 0 for readout. I can't imagine two sensor are bad. I only checked the two for now.



I would like to confirm that things are good working order so I am not chasing unknowns.


The rest of my caliper parts arrived today so I can start rebuilding them.



Thanks Guys!!!!
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post #39 of 201 Old 21st December 2018, 11:58 PM Thread Starter
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I Googled 'How to test a diode with a multi-meter'. It seems to be so simple to do.... I put brand spanking new batteries in my meter and went after the wheel speed sensors (AKA Pulse generator, ABS sensor). I disconnected the sensors at the wheel wells and tested the sensors (all four). All the meter showed at all locations and reversed terminals was .0L. All I can conclude is that all four diodes are toast? I did a parts search and see that there is a very wide range of prices by the different manufacturers. I will shop middle of the road prices from RockAuto.com. First thing I will do when I receive the new sensors is test them with the multi-meter. I better get a reading or I will be major PO'ed.


I better get some Aspirin now....
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post #40 of 201 Old 22nd December 2018, 01:07 AM
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Explain how you tested might be easier than me typing out how to test a diode. Include what ohms scale you used on your meter.
I will also give you a save from another forum to read most the links point to the wrong place. I did not really know how to save things like this when I did it. I hope this works, I am sending it as a zip because I don't know another way. You will have to unzip and you will get one folder with pics and an html file, they must be in the same folder.
ABS Help.zip

Three tries later and it worked.


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