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Hi Guys,

Need some help diagnosing a right front brake issue with my beast. I took the car in to the shop to have some work done, squaring the setup with new wheels, tires, spacers etc...The shop did an inspection on the car and found the brake fluid measured bad with 3% water contamination so I asked them to flush the brake fluid and replace. The shop came back with the following:

During the brake fluid flush this afternoon, my technician discovered that the passenger side front brake caliper appears to be stuck; not only was the fluid not coming through the bleed valve, the caliper piston was not moving so even with the brake pedal pushed down that wheel was able to spin freely.

After more diagnosis the shop came back with these notes and they have not been able to diagnose the problem.

  • Disconnected caliper flex hose from hard line, found only residual fluid inside (no new fluid came through with brake pedal application)
  • Reconnected hose and attempted to manually activate ABS pump through Autologic scan tool
- Pump heard switching on for a couple of seconds, but would turn off and Autologic displayed an error message ["Error activating front right (160)"]
- Checked for stored faults and found one:
- (5A) 90 Brief power interruption, frequency 1
  • Cleared fault and attempted to activate pump again, no change in pump function but no fault code returned
  • Disconnected hard line from ABS pump and verified good caliper function with pressurized air
  • Issue does not appear to be between ABS pump and caliper, most likely issue is internal to pump assembly or potentially between brake master cylinder to pump


I would like to add that I have not had any brake issues so I'm not really sure why this problem would be arising. Was there an issue with the brake bleed? Has anyone had any issues similar to this? Thanks!
 

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Has anyone had any issues similar to this?
Lots have. The module could have failed and left a valve open that should be closed or the hydraulic side could have failed. When or where these things happen is a guess, and could your shop have done something to bring it out, yes, but it was not a mistake. When you move large volumes of fluid that can be enough to bring the fault out.
Generally there are no codes thrown, it is like the car does not know there is a fault.
Try and get a used unit because new ones are expensive. There is an option to have them rebuilt but a few of the popular places who rebuild have closed their doors and hung the out of biz sign.
 

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My apologies, what unit/module should I try to get?
The combo unit ABS and DSC technically it is called the DSC III. The same thing your mechanics are calling the pump, they must work on Mercs a lot.
Here is the basic manual that came with the car. If you want more detail I have several others dealing with how it works.
 

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Problem is you can get a dealer to reman your controller, but the hydraulic section( where I suspect your problem is) is not available separately.
Part 1 is the complete unit. In canuk bucks they run around 650 used which is not too painful, I would leave it up to the shop or at least talk to them. They need to be able to install it which requires a tool that will talk to the unit and activate it. I don't remember but I think it also must be coded to the car.
Besides that they need to figure out if it is the controller or hydraulics that is bad.
34516769536
is the complete unit
The number you posted is just the controller hard to say what is failed without having the car in front of me.
 

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Problem is you can get a dealer to reman your controller, but the hydraulic section( where I suspect your problem is) is not available separately.
Part 1 is the complete unit. In canuk bucks they run around 650 used which is not too painful, I would leave it up to the shop or at least talk to them. They need to be able to install it which requires a tool that will talk to the unit and activate it. I don't remember but I think it also must be coded to the car.
Besides that they need to figure out if it is the controller or hydraulics that is bad.
34516769536
is the complete unit
The number you posted is just the controller hard to say what is failed without having the car in front of me.
DSC module does technically need to be coded to the car, but should operate without the coding if I remember correctly. I know I've had to replace mine once before, I THINK I coded it with NCSexpert, but I also still get a "versions do not match" warning when I query the module with INPA. No codes are stored and everything works, so I just ignore it.

I'd lean towards a stuck valve on the hydraulic side. You should be able to easily source one from Adam (Clemster on here).

Re: bleed procedures - I just did this last night in hopes I had some trapped bubbles (there were a couple tiny ones out of the fronts). I use the vintage DIS program which has a specific function program for DSC bleeding. Interestingly, it does NOT operate by activating a specific brake (front/rear or left/right). They describe the order in which they recommend you bleed, but when you perform the function, it simply activates "something" on a constant and the pump runs 3 times on an interval. It might be 5 seconds off, 3 seconds of run time and then repeats. I think it triggers all 4 valves at once, to be honest. This could be easily proven. I'll probably try it before my next HPDE (I have one starting tomorrow, hence the quick bleed/flush last night). The program also notes that if any work in front of the DSC module is carried out, that you need to activate the precharge pump first. I'll comment in the E65 master cylinder thread next.
 

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Lots have. The module could have failed and left a valve open that should be closed or the hydraulic side could have failed. When or where these things happen is a guess, and could your shop have done something to bring it out, yes, but it was not a mistake. When you move large volumes of fluid that can be enough to bring the fault out.
Generally there are no codes thrown, it is like the car does not know there is a fault.
Try and get a used unit because new ones are expensive. There is an option to have them rebuilt but a few of the popular places who rebuild have closed their doors and hung the out of biz sign.
Sailor which one recently closed up shop? The primary one I am aware of that has been used over and over again is modulemaster.com. Seems like they are still in business from their website..


There was a place close to me at one point in Taunton, MA, and I thought this was Module Master, but I guess not.. can't remember the name of the place either darnit.

Edit: google works! It is called "bba reman" - website here, but my lord they are getting filleted on google as far as reviews go, I wonder what the problem is over there...
 

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Sailor which one recently closed up shop?
Don't quote me but search it was in a recent post. I think it was BBA someone sent an inquiry too. The response they got was they are finishing what they have and taking no more and discontinuing that part of their biz.
I did not read your edit same info.
 
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