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Odd ABS/ESP behavior

10K views 23 replies 6 participants last post by  scotttherobot 
#1 ·
Hi folks,

I’m a new W211 owner with a 2005 E320 CDI. A few of you just helped me fix an underboost issue on this car which appeared during my drive home from purchasing it. Turned out to be a leak in the charge air system. Now I'm having issues with ABS/ESP.


I live in the mountains and work in the silicon valley, so my commute is twisty mountain roads and also bay area freeways. The first morning I drove the car to work on highway 85 in stop-and-go traffic, I managed to lock up the brakes while going about 15mph and I barely stopped before rear-ending a Civic. The tires made a godawful squealing and people stared. Embarrassing! That same day on my way home while coming down a compound corner on a mountain road while coasting at about 30mph (no pressing of either pedal), I hit a pothole with my driver’s side front tire which seemed to trigger the ABS/ESP to do some CRAZY stuff including locking up different wheels independently. It seemed to go back to normal, but after 1/4 mile I took another turn and the wheels started locking up again. It made me uncomfortable enough to pull over because I started to think I might have had a flat. Until then I had been doing this same 60-mile commute in two different W123s for thousands of miles with zero issues nor similar scares.

Since then I’ve had several “traction control events” and I have not developed any trust for the car. What concerns me is that the ABS seems to be not working at all. The ABS on my previous cars that had it worked by pulsating the brakes. Is the Mercedes system different? Or is it just broken? There’s no light on the dash being illuminated and no code being thrown.

We put the car on STAR SDS and dug around looking for codes in the braking/traction system. Running an “inspect brake system for air” showed some air in the rear brake lines! I figured perhaps that might be triggering my ESP issues — the rear wheels aren’t being braked enough and so the ESP thinks they’re slipping and activates the traction control before ABS has a chance to kick in.

We did a brake fluid flush and bleed today, and there were no obvious bubbles that came out from any corner. However, we did another “inspect brake system for air” and sure enough, SDS reported almost the exact same readings showing air in the rear brake circuits are shown!

Attached is a photo of the STAR readings from the “inspect brake system for air” diagnostic. It shows the word "speicherdruck" which apparently means "accumulator" -- coincidentally the name of one of the SBC parts that is known to fail.. Does anyone have any experience with these symptoms and have ideas for what it could be?
 

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#2 ·
Well, since my last post, we've made little headway. We tried bleeding the brakes, per the STAR DAS instructions, and it didn't seem to fix it. So we tried again. And again. We bled the brakes three times. Each time, the DAS test pictured above showed the same results.

Desperate to have my car back (I've been driving our E39 BMW, not so great on fuel), my partner took the car to a local indy (who himself has an '06 W211 with SBC) while I was at work today. I heard a harrowing retelling of the diagnostic procedure used by the mechanic, which included spirited driving and slamming on the brakes at 80+ MPH, causing ESP to kick in and the car to pull itself into another lane of traffic.

The mechanic's opinion was that the brake issues reported by STAR are a red herring, and that our real issue lies in the front left wheel/brake. He thinks there's either a malfunctioning brake caliper (sticking, rusty, etc), a malfunctioning ABS/speed sensor, or some combination of those, and he was confident that we could fix it ourselves.

Doing some googling for "W211 brake lockup" (why didn't I think to google this before?) reveals threads of people having almost the same symptoms as me! Their solutions were either to replace the speed sensor of the affected wheel, or to replace the "yaw sensor" in the center console of the car. Generally their efforts started with inspecting and cleaning the speed sensor, so my partner pulled the wheel to have a look.

With the wheel off, he discovered that pumping the brake causes that caliper to make a creaking noise, and visually it does not appear to be moving. The car had a brake job shortly before we bought it, so he's going to pull the caliper and make sure the pads were fitted correctly. If not, we'll be replacing the caliper and brake line just to be safe.

I ordered the yaw sensor as well to have on hand in case. I'm going to order a wheel speed sensor as well just in case. We'll see!
 
#3 ·
Today we did some more diagnosing. We pulled both front wheels and removed the brake pads and calipers to verify their installation and compare them to each other. No one of the calipers appeared obviously bad or seized. We put new grease where grease should go, and put everything back together.

Afterwards, we did some DAS diagnostics with the car in motion (STAR laptop on my lap in the passenger seat, etc) to verify that the wheel speed sensors seemed to be good. All four sensors reported values within .1 km/h of each other, so they seem fine.

Next, we did some good old fashioned braking with ESP on and off (in diagnostic mode, enabled by SDS). What we found was very interesting: On hard braking (when the bad behavior is happening), only ONE of the wheels locks up, and it's the right front. All four of the other wheels turn smoothly, but the right front wheel stops moving and leaves a skid mark. Not sure what to make of that.

The replacement yaw rate sensor arrived today, but I didn't realize that installing it requires removing the passenger seat. Not in the mood to do that.

Does anyone know what the likelihood is that the yaw rate sensor is indeed bad, but it's not causing a code to be thrown? We're getting ready to take the car to the dealership ($220 just for diagnosis, even if they turn out to be wrong!) at this point.
 
#4 ·
Okay, this is turning into the car from freaking hell. After conferring with the indie mentioned above and telling him that the wheel that locks up changes (it was the front left when he drove it, the front right when we tested in our driveway, etc), he admitted that the fault must be somewhere in the heart of the braking system, and was probably a malfunctioning valve body in the SBC pump. He said that sometimes, they fail without throwing codes and in mysterious ways. Go figure.

So ignoring the fact that the cycle count on the pump already in the car was very low (to sleep at night, we decided the count must have been reset without the pump having been replaced, certainly, which is why it must be failing now because it's actually very old, indeed) we bit the bullet and ordered a replacement SBC pump from our friendly neighborhood Mercedes-Benz dealer. They're always good sports about haggling so we got a couple hundred knocked off the price (still a 5-digit number).

My partner picked up the part and eagerly ripped the old pump out (disabling SBC with SDS first, safety first!). This is where the real fun began.

Upon re-fastening the final brake hardline, disaster struck! The brake line fitting cross-threaded. Very badly. Fearing the worst, we tracked down a tap and die set for the M10x1.0 threads and chased out the threads. The fitting was a gonner, but the port on the SBC was thankfully undamaged. So we cut off the end of the hardline with a rotary tool, cleaned it up, slid on a new fitting, and attacked it with a metric flaring tool. Those SBC brake lines must be hardened steel or something because there's no way you can flare them with a normal tool. Time to get a new hardline.

Thankfully, the line in question is one of the lines between the master cylinder and the SBC pump. Some of the other lines require removing the engine to access, per FSM. A call to the same friendly neighborhood Mercedes-Benz dealer got us the part ordered, and there was one sitting in Germany waiting to be sent to us. Estimated delivery, 10 days.

10 days later, we get a call from Mercedes. The part wasn't there. The "new guy" in parts had placed the order wrong. They reordered it, rush shipping. 3 days. 3 days later, no part. They don't know where it is. The parts manager called Germany and found out that they actually had none and had to make some, but it would definitely be there soon. It was finally supposed to be here last Friday (the 7th), for sure, but it wasn't. Then Monday, the 10th we got a call letting us know it won't be here until the 21st.

Fed up, we called a German wrecking yard in Sacramento, and they had the part for a cool $25. Why didn't we do this in the first place? Today my partner hopped up there and back to get it, and we slapped that sucker in (yes, bleeding the brakes for the dozenth time).

And it didn't fix the problem.

The brakes feel a lot better than before, however. The pedal is firmer and it's harder to make the car do the lock-up skid action that this whole thread is about, but it still does it if you try. SDS still says "Function of SBC is not assured" and claims that there is air in the rear brake circuits. On the bright side, at least we'll never have to replace the SBC pump in this car for another 10 years!

I guess now we start replacing calipers?? We're kinda at a loss.
 
#5 ·
I guess now we start replacing calipers?? We're kinda at a loss.
I would have tried this at first place. I think its not mention too many time in US forums but at least in Finland it is very know issue that rear calipers stuck after any maintenance. Culprit is usually material of pistons, which does kinda 'bulges' and does not allow piston to move freely. Many many times unexplained caliper problems were solver by only replacing whole caliper system, and my local indy is now doing it immediately when customer complains problems (may exist for example after pad change).

Only thing what was new to me in your case is that DAS is seeing problem as a air in system...
 
#6 ·
I think it's time to go to the dealer for a diagnosis.

We replaced both rear calipers and both rear rubber brake hoses. Same exact behavior. DAS claims there's air in the rear brake circuit and gives the same exact readings. Wheels still lock up when slamming on the brakes :(

At this point, the SBC pump is new, one brake hardline is new (from the master cyl to the SBC), two rear calipers are new, and two rear rubber brake hoses are new. There's not much more to the system, so I'm just kinda stumped at this point. Should we replace the front calipers as well? Or just take it to Mercedes? Is there something else it could be that we're overlooking?
 

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#8 ·
Only one thing came up my mind, but I think you would have noticed it when you changed parts; brake pipe is very prone to corrode in place where it goes behind plastic trims from rear wheel. Pipe could be not broken yet but 'sweating' and thus system thinks there is air in system. But on the other hand pressure is now good, even slightly leaky pipe should be seen as dropping pressure...
 
#9 · (Edited)
FYI there is no pedal pulsing in the ABS of an SBC system. Even though the caliper is pulsing you can't feel it in the pedal.
 
#10 ·
Okay, well, taking the car to the dealer did not go as well as planned. They quoted a $220 diagnosis fee on the telephone. We shopped this price around and it seemed average. So on Monday we called a tow because it was raining and had the car towed in. They promised a diagnosis by 3pm, no problem, however the service advisor said that the diagnosis fee was actually going to be $400... Yikes. So since we had gone through the trouble to get the car there, we said sure. 3pm rolls around, no diagnosis. The techs hadn't even touched the car yet. That they lied about the price, lied about when it would be done, and on top of that were generally rude and smug made us have second thoughts. So we got the keys back and had the car towed home with no diagnosis, much to the service advisor's amazement. Oh, and the tow truck on the way home dented the front left fender and wore off a chunk of paint because of an improperly-aligned tow strap. Great. :(

We called our indy and asked when he could look at it. He was booked out for a couple weeks, but gave us a pep talk that convinced us to try again. He suggested clamping off the front calipers one at a time and test driving. Clamping off the right line made nothing change. Clamping off the left line made the car pull hard to the right when braking. Not sure how conclusive that is, but it was enough to help us decide to replace the front calipers and hoses.

Okay, well, ordering the calipers did not go as well as planned. We have come to learn that AutoZone employees are generally incompetent. So finally we got all the parts in today. We changed the front calipers and hoses, bled the system, and when checking the system for air... we got farther then before!! No more message about the fill status of the rear brake circuits being an issue. But some time during the "check fill status of pedal travel simulator" test there was an error, and the suggestion was to re-bleed the system. Not doing that.

We drove it and it has the same issue. But at least now we know that all four calipers and hoses are good and the SBC is new. Maybe this isn't a brake system problem after all? This sure has been an expensive investigation.
 
#12 ·
It may be elementary but it is important!

All wheels and tires are the same, fronts are at about 50% tread and rears are about 70% tread (as in tread remaining, not tread worn). We have rotated them front to back and no change was seen. SDS reports speed sensors are good (we inspected and cleaned them all, and drove with SDS connected and all reported the same speed within a few tenths of a mph.

We put the car on the lift and looked at the suspension after someone on another forum suggested it (Humble Mechanic on Facebook) and everything seems tight and in good shape there. However, the driver-side engine mount failed this week and spat brown fluid all over the garage floor :( Could the failing engine mount be causing a weight imbalance/shift maybe?
 
#13 ·
Today we swapped the front right and left brake rotors. When the wheels lock, the car pulls to the left, so the thought was to rule out rotor issues. While we did not swap the rear rotors, we saw no change in behavior and the car still pulls to the left. The right wheels are currently not locking up (though they have before), just the left.

Here's a short video showing the two left wheels locking up in my driveway.
https://www.dropbox.com/s/484v5yjb1k7sojr/e320_skid.mov?dl=0

Something interesting. In the SBC "shadow memory" we see these old cleared errors. "Fehler geloescht" means "error cleared" and "Fehler trat vor 5 Zuendungszyklen auf." means "Error occured before 5 ignition cycles". I do not know what the error numbers actually correspond to (trying to look into that now) but maybe this will shed some light on what errors have popped up before.

Another thing interesting is that SDS shows 0 pressure for the rear wheel pressure sensors. We tried this with the car off and on and saw the same readings both times. Not sure what's up with that, when we bled the brakes it checked the pressure and it all looked good at that time.
 

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#14 ·
I have seen zero pressure in rear calipers once, but in that case there was also other errors and malfunction of SBC (circuit 30, red alert on dash, pedal flooring etc). Culprit was low voltage of SBC unit. Now you are not having any other errors but perhaps its still worth to check out SBC connector and see there is no corrosion. Also grounding of SBC unit is prone to corrode and causing voltage problems.

Its like rear control valves are not opening at all but in that case there should be SDS errors IMO...

I think error in 5 ignition cycles means that error was triggered once but when it didn't appear again during 5 next start, warning/error was cleared. At least this is procedure for example with EML/check engine light.
 
#15 ·
I've no experience with SBC system. You have touched or replaced everything save the master cylinder.
As I understand it 90% of the braking effort by the driver is seen by the SBC which then applies the necessary braking force to the calipers modulated by wheel speed/slip. The remaining 10% or so imparts some 'feel' to the driver and also is a failsafe (along with seat suction) if the SBC fails.
Are there multiple outputs of the MC or just one?

Skippy
 
#18 ·
In normal operation its all electric. In emergency there is only front discs braking, by unboosted 'master' cylinder



http://www.cardiagnostics.be/-now/DAS-WIS_bestanden/Benz SBC Tool_bestanden/W211-SBC.pdf


Mersum1es,
Thank you for the document. Unboosted braking using fronts discs only would not be a happy moment. I suppose if one had presence of mind at that instance the parking brakes could be used as well.
I am presuming 1) parking brakes are present and 2) they are mechanical.

Skippy
 
#17 ·
I had similar experience in my old w210 (RIP) Rear brakes seemed to be possessed at times.I'm not sure if this will apply in your case but for me it turned out that the rear abs brake sensor bracket was resting on the rear c.v joint at times because the bracket that was holding the abs sensor line rusted off the brake shield plate and had no support what so ever. I guess the occasional "bouncing" of the line with the bracket was some how causing weird signals. I had to also change the caliper. When I fixed all the issues God killed my car. Compensation was fair so we Are OK.
Utmost respect for your perseverance in solving this issue!
 
#19 ·
They are just that. The same shoes inside of the rotor hat.

Just for giggles after doing brakes I left SBC disabled on my own car and took it for a drive. I was able to stop the car safely, but I have rugby player legs. If it was my wife or daughter I would worry. It took about 70-80% more pedal pressure. Not nearly as scary as when the brake lines to the rear on our ML430 corroded and sprung a leak with my wife driving. The brakes were totally useless at that point.
They do drive my E500, however I told them if they ever see a brake message pop up in red to stop the car and call me or a tow truck to get it to the shop.
 
#20 ·
Scotttherobot,
While we drifted away from your original thread I recommend a read of a similar problem of brakes self-applying in the W164 forum. Recent thread.
In that situation the yaw sensor and/or chafed wiring in the steering column contributed to the problem.
Not you model, but may provide food for thought.
Skippy
 
#21 ·
Yeah, so I have read that and I've even ordered the yaw sensor! It's been kicking around my garage for a while, I haven't even opened the box. When it arrived, I realized that to replace it in the W211 it requires pulling the entire passenger seat and removing a chunk of the interior, as the sensor sits between the center console and passenger seat. We haven't found the time do that just yet.

We have an appointment to have the car diagnosed by the dealer on Wednesday 5/3. We're just so over it at this point. It's definitely not cost effective but we can't afford to be down a car for much longer. :(
 
#22 ·
IT'S FIXED! The dealership tech figured it out pretty quickly. Turns out, several of the brake hardlines were connected in the wrong spots at the SBC pump. How stupid.

You may recall that we replaced the SBC pump in the process of attempting to fix this issue -- yes, that's right, they were connected wrong before we replaced the SBC pump! We took photos during and after the replacement which show us putting the lines right back in the wrong place. That's what you get for not double-checking!

The dealership wouldn't give us hard copies of the car's records since we're not the original owner, but they did tell us that the SBC pump was replaced on this car sometime in 2012. That was before the previous owner had even bought it. Crummy.

Now to fix the freshly-failed motor mounts so I can finally start driving it!! Thanks to everyone for their help! This has been very stressful for us.
 
#24 ·
@;

We got clarification today from our service adviser. "They" (some Mercedes dealership) advised replacement in 2011 (not 2012 as I earlier reported). "They" did not do the replacement, but they acknowledge that it was definitely replaced between then and now by a third party based on the cycle count shown in SDS. The pump we removed was too young to be the original.

We contacted the previous owner to tell him the car was finally back on the road (this isn't the only issue we've had with it since purchase) and he said that he experienced this issue a couple of times, and he even replaced the control arms to attempt to fix it (we were also advised it might be suspension related on other forums) but he never had the SBC serviced and that it was definitely done by the owner before him. The CarFax timeline agrees. Oh well.

The dealer also advised us that the brake rotors were wrong (solid vs ventilated) so today we replaced the rotors with the correct ones and threw in some new brake pads. Next week we'll replace the failed engine mounts, change the oil, and I'll start commuting it it like I intended to do 4 months ago...
 
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