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E39 M5 and E52 Z8 Discussion 1998-2003 Advertiser's Forum

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post #31 of 45 Old 9th April 2019, 07:22 PM
bdiefAZ
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Engagement is higher, no sink to the pedal. I think if the pedal is sinking your master cylinder may need to be replaced due to internal "leaks"
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post #32 of 45 Old 9th April 2019, 08:27 PM
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Originally Posted by bdiefAZ View Post
Engagement is higher, no sink to the pedal. I think if the pedal is sinking your master cylinder may need to be replaced due to internal "leaks"

I will have to think 'replacing the MC' over as I just did that a few months ago while trying to resolve the sinking pedal issue. I bought the Genuine BMW MC from Pelican Parts that cost about $470... I bench bled it several times but the sinking pedal was there from the get go.


The cheap $76.72 MC scares me, but I also don't want to over spend either. I don't know which way to go. I may wait till I can run the DIS v57 software and see if there is any improvement.


Thanks!
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post #33 of 45 Old 10th April 2019, 07:54 AM
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Mr G,

Have you replaced all of your brake hoses on the car, including the 2 under the hood on the passenger side of the engine near the abs pump?

I am not a professional mechanic, but to my knowledge, the major sources of pedal sink are: hydraulic leaks - either external or internal, expanding rubber hoses, or air in the system. I use a power bleeder that pressurizes the reservoir on the master cylinder while adding fluid and have had good results with that method. I use ATE SL6, its a low viscosity fluid that is BMW backwards compatible, here is the ATE SL6 description (I do not track my car) hope this helps:

"The Ate SL6 fluid is a low viscosity formula for modern ABS and DSC systems. BMW recommends low viscosity brake fluid for all chassis beginning with the E60 5-series. Low viscosity (LV) is a thinner fluid that works better than a normal fluid in the small channels and passageways in the ABS/DSC pump. Using the heavier fluid will result in a delayed response to ABS and DSC activation and a spongy feel in the brake pedal (only during ABS stops). Ate SL.6 falls just short of DOT5 specs so is classified as a DOT4. It can be mixed with other DOT4 or DOT5.1 fluid. For track use, a heavier high performance brake fluid such as Ate Typ 200 or Motul RBF600 or RBF660 is recommended because of their higher boiling point and because the thicker fluid will thin out at track temps. But for street use we recommend switching back to a LV fluid, especially in colder climates."
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post #34 of 45 Old 10th April 2019, 05:08 PM
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Quote:
Originally Posted by bdiefAZ View Post
Mr G,

Have you replaced all of your brake hoses on the car, including the 2 under the hood on the passenger side of the engine near the abs pump?

I am not a professional mechanic, but to my knowledge, the major sources of pedal sink are: hydraulic leaks - either external or internal, expanding rubber hoses, or air in the system. I use a power bleeder that pressurizes the reservoir on the master cylinder while adding fluid and have had good results with that method. I use ATE SL6, its a low viscosity fluid that is BMW backwards compatible, here is the ATE SL6 description (I do not track my car) hope this helps:

"The Ate SL6 fluid is a low viscosity formula for modern ABS and DSC systems. BMW recommends low viscosity brake fluid for all chassis beginning with the E60 5-series. Low viscosity (LV) is a thinner fluid that works better than a normal fluid in the small channels and passageways in the ABS/DSC pump. Using the heavier fluid will result in a delayed response to ABS and DSC activation and a spongy feel in the brake pedal (only during ABS stops). Ate SL.6 falls just short of DOT5 specs so is classified as a DOT4. It can be mixed with other DOT4 or DOT5.1 fluid. For track use, a heavier high performance brake fluid such as Ate Typ 200 or Motul RBF600 or RBF660 is recommended because of their higher boiling point and because the thicker fluid will thin out at track temps. But for street use we recommend switching back to a LV fluid, especially in colder climates."
The question was not directed at me, however I have replaced all the brake hoses on my car with braided stainless including the two behind the pump, and all my hydraulic components are new. This is an interesting point about fluid viscosity...I run Motul RBF600 fluid, I wonder if bleeding this system when its heat soaked would allow for more effective purging of the ABS/DSC?

2002 Beast Schwarz-Metallic/Blk Sport
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post #35 of 45 Old 10th April 2019, 05:14 PM
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Quote:
Originally Posted by bdiefAZ View Post
Mr G,

Have you replaced all of your brake hoses on the car, including the 2 under the hood on the passenger side of the engine near the abs pump?

I am not a professional mechanic, but to my knowledge, the major sources of pedal sink are: hydraulic leaks - either external or internal, expanding rubber hoses, or air in the system. I use a power bleeder that pressurizes the reservoir on the master cylinder while adding fluid and have had good results with that method. I use ATE SL6, its a low viscosity fluid that is BMW backwards compatible, here is the ATE SL6 description (I do not track my car) hope this helps:

"The Ate SL6 fluid is a low viscosity formula for modern ABS and DSC systems. BMW recommends low viscosity brake fluid for all chassis beginning with the E60 5-series. Low viscosity (LV) is a thinner fluid that works better than a normal fluid in the small channels and passageways in the ABS/DSC pump. Using the heavier fluid will result in a delayed response to ABS and DSC activation and a spongy feel in the brake pedal (only during ABS stops). Ate SL.6 falls just short of DOT5 specs so is classified as a DOT4. It can be mixed with other DOT4 or DOT5.1 fluid. For track use, a heavier high performance brake fluid such as Ate Typ 200 or Motul RBF600 or RBF660 is recommended because of their higher boiling point and because the thicker fluid will thin out at track temps. But for street use we recommend switching back to a LV fluid, especially in colder climates."

bdiefAZ,


Thanks for your reply... As to your questions, I did replace the two short flex hoses. All of the other brake lines were replaced maybe twenty years ago with stainless steel braided lines (Teflon inner hose) and do not show any leaks or line damage. I also use a power bleeder to flush the fluid every two years. Since almost from the beginning (bought new in 2002) I have been using Motul RBF600 fluid with no issues. All went to hell about six months ago when I tried to flush the ABS/DSC unit. I used INPA and Rheingold software to activate the unit, even had the whole ABS/DSC assembly sent out for testing and repair. None of this made any difference with the pedal sinking way down. I did order DIS v57 software to maybe get better results shaking/flushing any air trapped in the ABS/DSC assembly. A few months I did take my car to a independent local shop to check this out. He used a version of Rheingold and pumped a liter or so of fluid with no improvement.



There are no fluid leaks, calipers were just rebuilt, pads are very new. The stock genuine MC is brand new too.



Over these last six months I have flushed quite a lot of the RBF600 through. I switched to a cheaper Valvoline DOT 3&4 brake fluid until all of this gets sorted out, then I will switch back to RBF600.


I really hate to be just throwing more money at this. I now wish I never attempted flushing the ABS/DSC assembly!!!! This should Not Be This Difficult!!!!


Any extra thoughts are welcomed!!!!
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post #36 of 45 Old 15th April 2019, 11:55 PM
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Update:

Stefan and I installed the MC on a second car, his 540T with e39 M5 brakes on the front/rear with braided hoses. Stock pads on front, EBC Red on rear. Car was bled with ATE SL6 fluid, noticeable braking improvement with the new master cylinder.
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post #37 of 45 Old 21st April 2019, 03:34 AM
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Update - I've got the MC installed, however the adapter I bought is not deep enough to accept the brake line fitting. The one I bought is: Female(M10x1.0 Inverted), Male(M12x1.0 Bubble). Should I be looking for a Female (M10x1.0 Bubble), Male (M12x1.0 Bubble) like these:

https://www.ebay.com/itm/Brass-Metri...YAAOSwidFazhck

https://www.summitracing.com/parts/edd-267000/overview/


Thanks in advance!

Last edited by jmarch; 21st April 2019 at 07:46 AM.
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post #38 of 45 Old 22nd April 2019, 05:37 AM
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post #39 of 45 Old 22nd April 2019, 06:35 AM
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Quote:
Originally Posted by mr_g_bock View Post
Also, I checked various web sites for price and availability of the two MC part numbers for Genuine BMW parts. I see for the *****650 part number, a price of $76.72 from ECS Tuning and Turner Motorsport. For *****926 part number a price range of $182.00 from OEM Bimmer Parts and $386.25 from Pelican Parts. Any idea why so low to so high???

I really want to get the brakes back to normal at least if not improved.

Thanks!!!!

RealOEM does not list *****650 at all... number not found... however, *****926 is found.

See attach screen shots of BMW PNPC runs of the 2 numbers... up to a 6x higher price for *****926.
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post #40 of 45 Old 22nd April 2019, 09:16 AM
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