My Brake Pedal Feel is Kicking My Butt... - Page 16 - BMW M5 Forum and M6 Forums
E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #151 of 209 Old 23rd April 2019, 01:39 AM
tallfreak
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I had the same issue with my m5 a few months ago. What ended up fixing the issue was bleeding the DSC hydraulic unit and the pre-charging pump. I think the pre-charging pump is what fixed it because I had tried the hydraulic unit once before with no luck.

I have an Autologic and ISTA, but I dont know if there is any aftermarket software available that will let you do it.

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post #152 of 209 Old 26th April 2019, 03:17 AM Thread Starter
mr_g_bock
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I have been trying to get DIS v44 up and connected to my M5 via USB cable. It is hit or miss with the connection. I hope to have this sorted out soon.


I am also looking for detailed written instructions on just how to perform the DSC flush and bleed.


I did try the INPA DSC pumps and valves activation a while back with a power bleeder attached with no improvement. Of course I could not find any detailed instructions for this either!!!


Any help with this would be appreciated!!!!!
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post #153 of 209 Old 26th April 2019, 04:12 AM
Rosie
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Here are the instructions:-

https://www.newtis.info/tisv2/a/en/e...lation/AryWRXx

In DIS go to Service Functions - Chassis - Brakes - Bleeding/Ventilation.

Bottom line is:-
Attach Pressure Bleeder and set at 2 Bar.
Open rear right bleed nipple (with catch bottle attached) and activate bleed procedure in DIS.
Once DIS procedure has finished pump brake pedal 5 times.
Close bleed nipple.
Then do it all the same on rear left, front right and then front left.

It is a lot easier with a 2nd experienced person.
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post #154 of 209 Old 30th April 2019, 10:41 PM
OjaiM5
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I was able to fix my issue. I rebuilt the calipers, brass guide, new booster and ECS lines. I excessively bled the system using a pressure bleeder and a scan tool.
Took it on a test drive in a safe area and did some 30-0 extreme stops, activating the ABS. The brakes were already working much better.
Brought it back home and did another bleed for good measure and figuring there may have been air kick loose.

Good luck with yours and I hope there is a resolution for you soon.
I am looking forward to not having bake fluid on my hands for a while.
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post #155 of 209 Old 10th May 2019, 03:45 AM Thread Starter
mr_g_bock
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No progress going on.... Still having issues getting GT1 DIS v44 communicating with the car, or VMware, DIS and the USB cable. Not all that simple and I am not any computer expert.


Also my car lift is still tied up with my 993 while the wheel rims get polished and re assembled. This is taking way longer than expected.


Maybe in a week or two... I will report in.
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post #156 of 209 Old 21st May 2019, 05:53 PM
Arktiksilber
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Quote:
Originally Posted by mr_g_bock View Post
No progress going on.... Still having issues getting GT1 DIS v44 communicating with the car, or VMware, DIS and the USB cable. ...


I use DIS v57. I don't think DIS v44 works at all with my setup. You MUST use the round plug in the engine compartment if you have it (even if you have one under the dash) and you MUST use a battery charger when you have the hookup running. Also NOTE: Plugging into the round plug requires a great deal of pressure. Make sure it is fully inserted.

DIS requires a minimum voltage in order to run. Mine delivers a “clean” 13.6 VDC and cost $300.00 (Midtronics PSC-550.) I’m not sure whether a POBC (Plain Old Battery Charger) is safe. Trying to program a module with a voltage that drops below a certain threshold during reprogramming can “brick” the module.

I had shoulder surgery on 4/30 and am just now able to sit at my computer. The last test I did was the DIS v57 test routine for the wheel speed sensors. This test involves actuating the test for each wheel in turn and then trying to rotate all of the wheels. All wheels should rotate normally EXCEPT the wheel whose solenoid is actuating in the ASC/T hydraulic module. This wheel SHOULD NOT TURN AT ALL. My test failed, in that I was able to rotate the (supposedly) locked wheel, though with difficulty.

Interestingly, as I rotated the wheel, my helper (who was holding the brake pedal down) reported that the pedal dropped as I did so. This is the first test I have run that manifests in anything related to the problem we are having.

While normally braking (without any active ASC/T control) the valve may be allowing pressure to bleed into the accumulator. I am able to generate very high pressures as I have reported in an earlier post but this is AFTER the pedal sinks close to the floor.

This makes sense, if the valve controlling release of pressure FROM the accumulator holds solidly. There are some very strange pressures indicated if I rapidly release the pedal and then slowly apply it again or if I release the pedal and then rapidly "stab" it.

Unfortunately, the failure of this test seems to indicate there is a problem with the mechanical portion of the unit. The electronic portion is commanding the selected solenoid to close as it should but the valve is not fully sealing and the wheel is allowed to turn. As the wheel turns, the ASC/T unit tries to stop the wheel by allowing more pressure into the brake line feeding the caliper (but the pressure is dissipated INTO the accumulator) and this causes the brake pedal to sink.

I had the ASC/T unit "rebuilt" but I never got any sheet detailing the test procedures the unit was put through, especially pressures. I plan to call them and will let the list know what they say.

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post #157 of 209 Old 21st May 2019, 09:41 PM Thread Starter
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Arktiksilber,


That is a lot of interesting information, but might uncover this brake problem.


I just recently got my GT1 DIS working. I was able to access my car with v44 or v57. My beast is back up on my car lift, all wheels off. In the next couple days I will be looking into running the DIS program to flush/bleed the system with software assist that will tell me what to do and when step by step (I hope).


I can't believe this is such a PITA.


Take care of your shoulder and hope you fell better!!!
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post #158 of 209 Old 22nd May 2019, 06:22 PM
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Quote:
Originally Posted by mr_g_bock View Post
... My beast is back up on my car lift, all wheels off. In the next couple days I will be looking into running the DIS program to flush/bleed the system with software assist that will tell me what to do and when step by step (I hope).

When you have finished the bleed routine, continue on into the wheel sensor test; Have your helper hold the brake pedal down and check whether you can rotate the wheel that is supposed to be locked. If so, see if the pedal sinks while he is doing so. You may have to put some muscle into it but ANY movement at all is a fail. The pedal will sink as the wheel turns.

This test is best performed with the road-wheel in place as you will need the leverage to make sure full hydraulic pressure is being applied to the caliper.

As I have said, mine failed this test. When I can get back to work (9 months according to my surgeon but what does he know?) I will check the wheel sensors on the wheels that failed (LR and RF) for proper function.

Hmmmm. LR and RF? That in itself may be a clue. Aren’t these systems diagonal? If one circuit fails the other is available to provide stopping power. Remember, the very first repair I attempted was replacement of the M/C with an OEM TRW (new.)

Quote:
Originally Posted by mr_g_bock View Post
I can't believe this is such a PITA.

The reason it is such a PITA is that we are reluctant to accept that everything we have done so far, points to the most expensive component; the ASC/T module (on mine) that costs $1750.00 new.

Hey! I’ve got a great idea. Why don’t YOU 😊 buy a new one and see if that fixes the problem? If it works for you, I won’t have to risk MY money on yet another failed attempt.

I have subbed the under-dash computer with a used unit without any change.

I have also subbed a used ASC/T unit without change. Suggestive but NOT definitive. I didn’t have a lift to do the wheel sensor test before I put the original unit back in.

One test I can't remember having done is to apply the brakes with the key off and then turn the key to the on position WITHOUT starting the engine.

With a vacuum in the booster: (Start the engine and turn it off. Press and hold the brake pedal. Then turn the key to the run position.) Does the pedal sink? and:

Without a vacuum in the booster: (Key off. Repeatedly pump until the vacuum is exhausted and hold. Then turn the key to the run position.) Does the pedal sink? Just a passing thought.

Quote:
Originally Posted by mr_g_bock View Post
Take care of your shoulder and hope you fell better!!!

Thanks for your kind sentiment. I had my right shoulder done in the past and so far, there is no surprise. At this point, I am climbing a solid wall of pain, sleeping, icing, reading and watching the clock go around and around.

Progress is incremental but will be more bearable when I am cleared to begin physical therapy.

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post #159 of 209 Old 24th May 2019, 04:08 AM Thread Starter
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I will try hooking up the computer and cable to the OBD II connector inside the car and run the GT1 DIS v5.7 tomorrow and see if I can access the Bleed Sequence. I don't have a power supply, but I tested my alternator output with the engine running and it was 13.7 volts. I will not be doing any programing so I feel safe not to brick the car computer.



I hope to have some good news soon.


A big thanks to everyone for the support and ideas on this issue!!!!
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post #160 of 209 Old 24th May 2019, 05:36 PM
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Quote:
Originally Posted by mr_g_bock View Post
I will try hooking up the computer and cable to the OBD II connector inside the car and run the GT1 DIS v5.7 tomorrow and see if I can access the Bleed Sequence. I don't have a power supply, but I tested my alternator output with the engine running and it was 13.7 volts. I will not be doing any programing so I feel safe not to brick the car computer.


IF... you have a round connector in the engine compartment you MUST use that one. The under-dash port will NOT work.

This program will refuse to initiate, if you do not have a minimum voltage on the battery. Run INPA to make sure everything is properly set up. You should have two filled in radio buttons on the startup page. Exit and then start DISv57.

The electronics sap the voltage very quickly and it may be that you won't be able to complete the tests before DISv57 aborts. I recommend you at least connect a standard battery charger while you have the key on.
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