DSC Recoding / Soft Brake Pedal - ISSUE RESOLVED

[wolverine2k]

Hi all,

Me again and my never ending work on this Z4. I keep thinking I'm almost there but maybe I should stop thinking that as something new keeps popping up. At this point, I feel like the car will be like Triggers broom.

My brake pedal was a bit soft/low so I followed some guy on YouTube on using ISTA to recalibrate my DSC. Well that didn't go too well and it failed on the second step and has now given me a 5DD0 error. I kept trying and it wouldn't go past the second step, keeps giving me this error:

Adjustment DSC unit - Separating Valves
=========================

The adjustment procedure could not be performed.

Possible causes:
- Brake was operated
- Leak in the brake system
- Brake system not bled
- Bleeder unit is still connected

None of these points are true.

INPA doesn't seem to have many options but I tried "Compensation routines" under the DSC menu and now I have 5DD2 to go with my 5DD0 error.

I've tried to reactivate with NCSExpert but that resolved nothing - I think I'm probably doing that wrong anyway.

Has anyone come across this before and can offer some advice? Do I look at replacing my DSC unit?

Thanks!

 

[enuff_zed]

Just a thought. You had a soft brake pedal and one of the potential causes of that fail is a leak in the system.
Are you sure there's not even the slightest leak? It is possible that an internal leak past a seal can cause issues without any visible signs and no loss of fluid.

 

[wolverine2k]

Just a thought. You had a soft brake pedal and one of the potential causes of that fail is a leak in the system.
Are you sure there's not even the slightest leak? It is possible that an internal leak past a seal can cause issues without any visible signs and no loss of fluid.

I've got no loss of fluid at all so this might make sense! Do you know what internal seals I should be looking into?

 

[enuff_zed]

Only ones I've come across, not on a Z4, were the master cylinder seals.
If you put your foot on the pedal and hold it there, does it slowly sink to the floor?
I assume you've already done a full bleed of the system?
The piston inside the master cylinder usually only moves a little way back and forth. Over time it builds up a tiny band of 'varnish' at the end of that travel. If you then bleed the brakes by pumping the pedal all the way to the floor then the seals in the master cylinder ride over the ring of 'varnish' and this can be enough to unseat them or damage them just enough to leak.

 

[wolverine2k]

Only ones I've come across, not on a Z4, were the master cylinder seals.
If you put your foot on the pedal and hold it there, does it slowly sink to the floor?
I assume you've already done a full bleed of the system?
The piston inside the master cylinder usually only moves a little way back and forth. Over time it builds up a tiny band of 'varnish' at the end of that travel. If you then bleed the brakes by pumping the pedal all the way to the floor then the seals in the master cylinder ride over the ring of 'varnish' and this can be enough to unseat them or damage them just enough to leak.

Yeah the brake pedal does eventually drop to the floor but only when the car is started and running. When the car is off, the brake pedal is hard and won't go past a certain level no matter how hard I push. If the master was leaking, it would still travel to the floor when the car is off right?

That's what made me think there's air in the DSC hence why I tried to calibrate it to try and get the air out.

I bled the brakes conventionally with a pressure bleeder but I've seen there's a bleed option in ISTA which I'm going to try a few times and see if that will resolve anything.

 

[wolverine2k]

Well 4 hours of bleeding with ISTA and I still have a soft pedal and DSC calibration is failing at "separating valves". Gone through 5 litres of brake fluid as well.

Tried to recode the steering angle sensor with Tool32 as well in case that was the issue (as it is with E90s). Didn't resolve anything.

5DD0 and 5DD2 still coming up.

I'm gonna change the master cylinder tomorrow and see if that resolves anything. Picked up a genuine used one from my local breakers. I hate bench bleeding so much and am going to be so annoyed if this resolves nothing

 

[Ewazix]

Once you have eliminated the common causes it's worth noting that BMWs can suffer soft pedal syndrome due to ABS pump failure. It can be intermittent and without directly related fault codes. I know several people on here have had their units repaired for various reasons, so cost is not necessarily horrific.

 

[wolverine2k]

Once you have eliminated the common causes it's worth noting that BMWs can suffer soft pedal syndrome due to ABS pump failure. It can be intermittent and without directly related fault codes. I know several people on here have had their units repaired for various reasons, so cost is not necessarily horrific.

I had a DSC pump failure on an E92 but that at least gave me the codes that the DSC pump had failed which made my life easier

Messy job but I bought one which wasn't even the same part number, swapped over the pump part, plugged it back in, cleared the codes and happy days.

Might do the same with this one but cheapest DSC pump is around £180 second hand. E92 ones were around £30

I would buy one, put the unit in and recode it but there's no sg_code options for the DSC in Tool32 that I can see. Oddly it was missing from the list.

I've swapped the master cylinder over so now I guess I'll try the DSC.

Apart from this the only issue I have is the stopper motor on the drivers side. Swapped it over and it's temperamental. I think the cables must have a break so looks like a rewiring job to add to the list...

 

[Ewazix]

Stick at it

 

[wolverine2k]

Stick at it

Yeah almost near the end of me tether.

Used ABS pumps that match my part number are £350+!! Not sure why when every other part number is £20-50.

6769162 6769164 are the part numbers. What's so special about this pump?

I notice I didn't have brake pressure sensors on my brake master cylinder but two bolts. Does anyone know if this pump has the sensors built in hence the ridiculous used price? Or is it just that they're rare?

 

[BumpyZ4]

What year car?

 

[wolverine2k]

What year car?

2007. I found a breaker who sold me a matching part number one for £100 so I've taken the plunge. I've already spent over a grand on parts and tools for the repairs I've been doing. What's another 100...

Now I need to decide if I try and code the vin to the 2nd hand one or swap the electrics. I'm leaning towards coding the vin on the replacement in case my electrics are buggered.

 

[wolverine2k]

Great - the part the breaker supplied is a totally different part number despite me confirming the part number I needed.

Back to the drawing board...

 

[Ewazix]

Great - the part the breaker supplied is a totally different part number despite me confirming the part number I needed.

Back to the drawing board...

As I mentioned others have had their own unit refurbished avoiding compatibility issues, that may be the way to go if someone can recommend a current repairer?

 

[wolverine2k]

Great - the part the breaker supplied is a totally different part number despite me confirming the part number I needed.

Back to the drawing board...

As I mentioned others have had their own unit refurbished avoiding compatibility issues, that may be the way to go if someone can recommend a current repairer?

I've contacted the usual suspects but not sure I want to spend as much as they're asking when they're all telling me that it "could" be my issue.

I've seen a pump repair kit that I'll do myself it it comes to that. It turns out that the ABS pump I have does have the brake pressure sensors built into the unit as well so I can't even use one from a different bm. Can only use par number 6769164 or 6778490.

 

[wolverine2k]

SUCCESS!!

Ok so I no longer have have a soft brake pedal and I don't have the trifecta lights on my dash anymore. I have an ABS light but that's my mistake that I'll cover at the end of my resolutions.

This was my journey - hope someone in future can learn from it and save themselves some money.

Step 1
Replaced all discs and pads. Resolved nothing.

Step 2
Replaced half the steel pipes with kunifer pipes. Replaced all the hoses with steel braided hoses.

Resolved nothing. They all needed doing anyway due to MOT failure so no sleep lost there and the piipes and hoses will last longer than the car now.

Step 3
I bled the car through INPA and couldn't see any air coming out.
Bled the car for hours and went through 5l of brake fluid and couldn't see any bubbles via ISTA+ and a pressure bleeder either.

Calibration kept failing.

Step 4
I changed the master cylinder which was an incredibly messy job and bench bleeding is never fun, especially with how much fluid you end up going through.

A complete and utter waste of time. Exactly the same problem and INPA or ISTA+ kept crapping out when trying to recalibrate the DSC. I should have stuck to my instincts that brake cylinders are unlikely to be the culprit in 3/Z series cars.

Anyone want to buy a perfectly fine master brake cylinder?

Step 5
Took the DSC pump out. Removing the wheel arch is the best way to do it. Gave it a few knocks, put it back in.

Resolved nothing

Step 6 - The Resolution
Now this is where it gets really interesting. I still suspected that even though there were no error codes suggesting this, the ABS pump was the culprit.

6769162 with a pump part nr 6769164 is near enough impossible to find for less than £400. I thought I had found one, but they sent me a totally different part.

So instead I thought I'd try something different. 6769164 has pressure sensors built into the unit and NOT on the master cylinder like other Z4s have. I started looking at other E90 ABS pumps and I found 6790147 (pump 6790146) which looks identical to my unit. It has the two humps which I assume are the pressure sensors built in.

6790146 has identical pump pattern to 6769164

I picked it up for £70. I installed it into my car with the ambition of recoding my VIN to it but I couldn't get any software to even detect it. Maybe I didn't plug it in properly but I decided to stop wasting time and instead swapped the pump unit onto my old electrical part.

So now I have a pump which is 6769162 electrical and a 6790146 pump.



I plug it into the car, it detects it so I decide to tighten all the brake pipes. I bleed only with a pressure bleeder. 1 litre through the brakes to get all the air out.

I load up INPA, run the calibration and the calibration all goes through fine and the errors are gone!! I drove it up and down the road and NO more spongy pedal!!! I feel like I can actually drive this car safely now!!!

So if anyone in the future finds this thread - you can swap your pump from a latter 3 series as long as the pump pattern is identical. 6790146 worked for me - should work for you too.

Last steps - anyone help with this?
Like a fool I was messing about with Tool32 before I pulled the DSC/ABS pump out and I somehow activated the end of line test. So now I have the ABS light on my dash and need to figure out how to run the end of line test to get rid of 5E00/5E01 code. I've read that I need to just hold the brake and go round a roundabout or something on this forum here: https://z4-forum.com/forum/viewtopic.php?t=97310

 

[Ewazix]

I can't help with your test query, but admire your tenacity and logic to fix the issue. Thanks for sharing

 

[Zulu4]

Very well done and thanks for sharing the resolution.
It's what makes this forum so much better than many other car forums, where people ask questions and are never heard of again.

 

[wolverine2k]

Very well done and thanks for sharing the resolution.
It's what makes this forum so much better than many other car forums, where people ask questions and are never heard of again.

Oh yeah. Imagine my frustration when I found my issue and the poster posted once and never came back. I've been trying to resolve this since end of Feb!!

One thing I'm finding annoying about this forum... Am I blind or where is the date/time of posts????

Update to 5E00 and 5E01 - RESOLVED
I tried all the tricks online that people used (all 3 of them) and it resolved nothing. I thought I activated end of line using Tool32 so maybe I could deactivate it?

Connected to the DSC, ran "bet_passive" with NO arguements and the ABS light turned off. Cleared the codes and now my only error code on the entire car is washer jet heaters or something useless. RESOLVED

I wish I had sorted out the reluctor ring at the back as the traction control constantly kicking in is annoying but it's not an MOT failure so that's next job once I get an MOT!

I am so close to finally getting this car back on the road!

 

[Sidewaze Samm]

Am I blind or where is the date/time of posts????

just at the top of the post...