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View Full Version : Brake pedal goes to the floor, 3rd new master cyl & booster, please help!


Ilia Barannikov
10-11-2013, 07:30 PM
Dodge Sprinter 2500 140wb

So... I was driving through the desert in nevada about a 2 years ago, and my brake pedal went to the floor, had the booster replaced, got back on the road, and in 50 miles, the brakes failed again. At that point we brought it to a more reputable shop where they told me the master had failed, they replaced it, and the brakes worked fine... for two years. Then, as i was driving through oregon, the brakes went out again, downhill on grants pass, my e-brake has never worked on the vehicle, it has been rusted out for a while and is seized up. I ordered a new master cylinder, and replaced it myself, bled the brakes and continued on my way, again, after 50 or so miles the brakes lost pressure and again, and had no brakes. I brought it into Midas, and they told me the rear pads were bad and the housing for one of them had been damaged, they charged me $400 for the repair and put me on my way, no more than 20 miles down the road, the brakes failed again. At this point they told me I had put the wrong master cylinder in, and the part i installed was for the non-tow package model, they actually made me feel dumb and told me they would replace the master properly and it would work, the next day, the shop had called and told me it was not the master, but the booster, that the center pin had come loose and was not engaging the pin on the master properly, ok, great, $700 later the brakes seemed to work fine. only about a week later, the pedal went to the floor again, brought it into a shop, they replaced the front right caliper, the master, and the booster, and the mechanic put me on the road again with a spongy pedal, which seemed wrong to me, bc this indicates air in the line, he assured me everything was fine, he said the parts they are manufacturing now are of poor quality and many times they are defective, now im in bakersfield ca, with the same problem. Could it be the ABS module?

There are NO leaks, the fluid reservoir is full and after bleeding, the pedal remains firm and slowly looses pressure. I can't see how the a bad ABS would make this happen, plus the part is $1500 and its not something i have the money for at this point.

Tomorrow, I am going to bypass the abs and put the lines out from the master directly into the brakelines, hopefully this will tell me if it is truly the abs that is the culprit.

any help with this problem would be greatly appreciated. I've driven down mountains with no brakes, and had to jump out in the middle of an intersection to try to stop my van with foot power, and really dont want to keep putting myself in deadly situations anymore. Please help :cry:

icarus
10-11-2013, 07:34 PM
How about finding a competent Sprinter mechanic? Perhaps an independent that specializes in Sprinters. Seems like you have been chasing your tail with substandard mechanics. Question is do Midas actually have the expertise to work on Sprinter ABS systems? I the of Midas as the cheap muffler place.

Icarus

Aqua Puttana
10-11-2013, 07:54 PM
How about finding a competent Sprinter mechanic? Perhaps an independent that specializes in Sprinters. Seems like you have been chasing your tail with substandard mechanics. Question is do Midas actually have the expertise to work on Sprinter ABS systems? I think of Midas as the cheap muffler place.

Icarus
I agree completely.

Who are these morons ... people?

To the best of my knowledge there is no special master cylinder related to factory tow package for the T1N. That said, you still may have installed an incorrect part.

Even cheap parts shouldn't cause a soft pedal. The incompetents probably didn't have the proper tools to include the ABS CAB HCU in the bleeding process.

There has been some history of the Sprinter ABS unit allowing air into the system. That could cause a loss of pedal.

The parking brake should be put back into working order.

Good luck. (Especially if you don't get to a Sprinter specific shop.) vic

Ilia Barannikov
10-11-2013, 07:55 PM
ive been on the road, living in my van, and have been working the music festival scene as a stage builder. Every time mechanics have fixed the problem it seems fine until i get far away enough to not be feasible to return to their shop. Bringing it to a dealership would also cost me an arm and leg. And at this point I've burned through the little money I started out with. :idunno:

Aqua Puttana
10-11-2013, 08:01 PM
... And at this point I've burned through the little money I started out with. :idunno:
You may be able to free up your parking brake fairly inexpensively.
Try this post.
http://sprinter-source.com/forum/showthread.php?p=95765#post95765

vic

Ilia Barannikov
10-11-2013, 08:04 PM
so i read some of the post regarding air getting in through the abs, and that seems to be the only option left after replacing all the other parts. I know its not the best idea, but people have been driving without abs for longer than they have with them, and to me (let me know if im crazy/dumb) if i bypass the ABS with flex brake line into t-block splitters right into the brake lines, that should stop the issue (if in fact it is a faulty ABS part). Let me know what you think, thanks for the responses!

icarus
10-11-2013, 08:07 PM
I'm sorry for your trouble, but the bad taste of a cheap price lingers long after! There is a reason that Sprinter Mechanics are not "cheap" because most of the time, most of the good ones do it right the first time. Often, in the net, cheaper than doing it wrong several times.

I m not an ABS expert, but from what I know the ABS system has critical issues that are not just as simple as installing and blending.

Icarus

Ilia Barannikov
10-11-2013, 08:11 PM
couldn't agree with you more, my mother always said "Im not rich enough to buy cheap ****", im looking at getting the parts in tomorrow, and unless someone can tell me this is a bad idea in my situation, I will bypass the ABS and will report on how it goes.

icarus
10-11-2013, 09:16 PM
I can't articulate why, but I think it is a bad idea. It just seems that it is a very sophisticated total system, and to just jury rig it sounds crazy IMHO.

I would pose the question to Dr.A or Dennis at Lynden Engineering, members here,

Icarus

Aqua Puttana
10-11-2013, 09:28 PM
... im looking at getting the parts in tomorrow, and unless someone can tell me this is a bad idea in my situation, I will bypass the ABS and will report on how it goes.
Of course the proper answer is that you shouldn't modify your brake system or by-pass the ABS system.

As a practical matter it may not be as easy as it seems. You have 2 ea. brake lines going from the master cylinder down to the CAB/ABS/HCU (I'll use HCU Hydraulic Control Unit from now on). One line is from each master cylinder section.

The HCU then feeds 4 ea. brake lines to the wheel cylinders. The brake system is designed to feed a diagonal set of wheels from each master cylinder section. The output is conditioned by the various safety systems (ABS, ASR, ESP including proportional braking).

To by-pass the HCU mechanically, you will need to combine the two diagonal brake feed lines to feed it with one section of the master cylinder, and then do the same with the other diagonal. So you need a Tee or Wye fitting with the proper threaded fittings. The 2 each brake lines from the master cylinder are larger diameter than the lines feeding the wheel cylinders. Matching fittings for your intended purpose may not be easy.

I have no idea what direct connection of the master cylinder to the wheel cylinders will do to proportioning the pressure for the wheel cylinders. Remember to use only high pressure fittings.

All in all it's really not a good plan in my mind.

Good luck. vic

icarus
10-11-2013, 09:36 PM
Me thinks it would be easier (and cheaper) to fix it properly!

Icarus

Aqua Puttana
10-11-2013, 09:59 PM
Me thinks it would be easier (and cheaper) to fix it properly!

Icarus
I agree.

Practically everything else related to bad pedal in his system has been renewed. The HCU/ABS unit does have some history of allowing air into the system. Changing out the HCU/ABS seems like a fairly logical next step for a DIY repair.

Perhaps given better diagnostic capability in both equipment and knowledge, more tests would make sense.

vic

Aqua Puttana
10-12-2013, 01:58 AM
Dodge Sprinter 2500 140wb

...

There are NO leaks, the fluid reservoir is full and after bleeding, the pedal remains firm and slowly looses pressure. I can't see how the a bad ABS would make this happen, plus the part is $1500 and its not something i have the money for at this point.

...

:cry:
Not that you asked.

To date the HCU/ABS leaking air into the system hasn't been a common problem. Based upon that, a used unit may be a good option. You don't say what model year. There are various used units listed on eBay. vic

http://www.ebay.com/bhp/sprinter-abs

lindenengineering
10-12-2013, 02:00 AM
Guys
Having read the thread I think it is time for someone qualified to take a look at them.

Having defective brakes can get you into some very serious situations even killing someone like a child, (fancy having that on your concience for life) or yourself for that matter.

Now for the record the ABS "brick" is a problem as (previous discussions) and usually bleeding is best done with a factory scanner. Now recently we got great success using a Pheonix brake bleed tool doing a reverse bleed. This was conducted on a Landrover LR3 which shares the same braking system as many Euro platforms including the Sprinter. In our case we didn't care too much if we screwed it up as we had the factory style scanner to fall back on and the factory bleed procedure to put it right.:thumbup:


http://www.youtube.com/watch?v=1LVyA_3lOmM



Now we have the Max Pro in the shop and the only comment I would mention is that the caliper must have clean fluid in it AND no contamination as you don't want to reverse bleed dirt into the ABS brick. Then bleed slowly and deliberately to purge the system.
I am going to have a go with this on TIN Sprinter shortly.
I will let you know how it works with a completely dry system.
Cheers Dennis

Ilia Barannikov
10-17-2013, 05:48 AM
ok, so I have made it back to San Francisco, the last two mechanics that tried fixing the sprinter (which is a 2003 2500 140wb w/ 170,000 miles) had replaced the master cylinder, and the brake booster, and the problem still persists. After a full bleed of all 4 wheels, the pedal is hard, this morning it was fine, and had good stopping power, I was in Los Banos CA, and drove to San Francisco, which is roughly 200 miles, in this distance, the brakes were at the point that when i arrived in Oakland I had about 5% stopping power, so I bled the front left wheel, and regained some pedal (enough to get me to SF).

*There is no air in the lines of any of the wheels besides the front left.

*When I open the fittings on the master cylinder, and have my GF pump the brakes (like bleeding the wheels) there is air coming out.

*There are no leaks in any of the lines.

*The master cylinder and brake booster have been replaced twice, but this has not solved the problem.

At this point, the ABS is the last thing in the system, but I can not wrap my head around how exactly air is leaking IN without brake fluid getting OUT.

**For all those who mentioned my idea of bypassing the abs system as being foolish and dangerous, here is my take on the situation, and please respond, I am a big boy and prefer honesty, if your perspective can elaborate more than just the potential danger to children, and my said guilt into the foreseeable future. Please, give me some data, or back your argument with science, preferably physics.

I have researched the ABS system, how it works, what it does, speed sensors, computer data analysis etc... Here are some points to illustrate my situation to you guys:

1-I'm not a rich man, the abs unit from the repair shop is upwards of $1800

2-I live in mid-southern California, it hardly rains.

3-ABS has almost gotten me into an accident before, I was in a lifted LR disco1 97, I turned out from a lane to avoid rear-ending someone, and almost did when the abs engaged and it took 40 feet to stop my vehicle from 45mph on dry asphalt.

4-I think ABS is bullsh!t, I think its nice for housewives that drive way too fast on the way to pilates, hopped up on lattes, in a large SUV, with no real driving skills. Its for people that panic behind the wheel and floor the brake pedal, I have been in 5 accidents, only one being my fault, so I am familiar with peoples reactions and can understand why ABS would be a good idea.
(please tell me if my opinion on this is skewed, I enjoy learning, and am not hard-headed)

5-I have lost work and over $1500 on this problem, and I have to drive 15 hrs to Washington state to try and make some cash before I take off to central america for the winter. I have to leave this friday, If i dont make it, my trip south might possibly not happen.

6-I have been put on the road 4 times, each time expecting the brakes to work, and have been EXTREMELY lucky that I have not got into an accident. (one time, last week, I lost brakes completely, and had to jump out of the van while it was going 5 mph through a busy intersection, i was trying to slow it down with my feet, luckily I was not killed) My vehicle is from Mass and was abused by a plumbing co before i acquired it, the body, and many parts are rusted to sh!t, including the emergency brake. I have learned the fine art of driving a vehicle many miles with absolutely no brakes, down shifting, throwing it into neutral and praying have become common place in my life.

7-One day, I will have money (hopefully) and will instal a proper ABS unit.

8-People have been driving without ABS for longer than with it, and there are many online (including me) who believe that ABS is actually more dangerous.
http://blog.sonicans.net/anti-lock-brakes/

Now that I am done with my rant, and hopefully have shed some light on my situation, I am asking for your help, if you do not agree with me, fine, let me know why, if you do on the other hand, PLEASE PLEASE PLEASE PLEASE help me! Hell, even if you dont agree with me, please help!

Here is the information I need:

*Any solid advice on why this is a bad idea.

*The specs for the brake lines, and fittings, coming out of the master cylinder, and in/out of the ABS unit . (I heard they were larger than the rest of them) Like if they are standard metric, etc and what sizes they are.

*If I should replace any of the brake lines, or if I can keep the existing ones. If I do have to replace, what kind of lines should i be looking at? Flexible ones? SS ones?

*I have found parts online that resemble what i need, mostly at classic cart parts stores, but they are all standard, and are made for older american cars. The abs unit has 4 lines coming vertically into the unit (two being the send from the master cylinder, and the other 2 going to one of the rear brake calipers), and two lines leaving horizontally towards the rear, which go to the front brake calipers. So the actual parts I need would be two t-block or 3-way fittings, and preferably would need the same basic configuration, two from top, one from the rear on each. If you can find something that would work, I would greatly appreciate it.

Thank you for reading all this, and if you have any feedback, that would be awesome.

NORTON
10-17-2013, 10:08 AM
After having the brakes bled and with a good solid pedal then driven a reasonable distance to get the brakes up to temperature and having them perform at only about 5%, then find air in the lines, points to the brake fluid being contaminated with water causing it to boil and creating bubbles in that area.
You would think that after all of the replaced parts and subsequent bleeding it may have replaced all of it, but unless done properly some could have remained.
Back in the early 60s as a teenager, my mates car would lose its brakes after stop start driving, it was a faulty brake light switch which was fitted to the hydraulic lines, shorting out and boiling the brake fluid.
I hope helps
murray

Aqua Puttana
10-17-2013, 01:29 PM
Ilia,
My assessment is that the ABS unit seals leak air in during operation, but seal properly when subjected to internal hydraulic pressure.

I outlined the difficulties of eliminating the HCU module.

I provided some eBay options for reasonably priced used ABS units.

Your rant set the tone for me.

Do whatever you want. vic

P.S. - What other factors may have been affected/"improved" by the "lifted" vehicle modifications as related to ABS? That example is not valid in my world.


ok, so I have made it back to San Francisco, the last two mechanics that tried fixing the sprinter (which is a 2003 2500 140wb w/ 170,000 miles) had replaced the master cylinder, and the brake booster, and the problem still persists. After a full bleed of all 4 wheels, the pedal is hard, this morning it was fine, and had good stopping power, I was in Los Banos CA, and drove to San Francisco, which is roughly 200 miles, in this distance, the brakes were at the point that when i arrived in Oakland I had about 5% stopping power, so I bled the front left wheel, and regained some pedal (enough to get me to SF).

*There is no air in the lines of any of the wheels besides the front left.

*When I open the fittings on the master cylinder, and have my GF pump the brakes (like bleeding the wheels) there is air coming out.

*There are no leaks in any of the lines.

*The master cylinder and brake booster have been replaced twice, but this has not solved the problem.

At this point, the ABS is the last thing in the system, but I can not wrap my head around how exactly air is leaking IN without brake fluid getting OUT.

**For all those who mentioned my idea of bypassing the abs system as being foolish and dangerous, here is my take on the situation, and please respond, I am a big boy and prefer honesty, if your perspective can elaborate more than just the potential danger to children, and my said guilt into the foreseeable future. Please, give me some data, or back your argument with science, preferably physics.

I have researched the ABS system, how it works, what it does, speed sensors, computer data analysis etc... Here are some points to illustrate my situation to you guys:

1-I'm not a rich man, the abs unit from the repair shop is upwards of $1800

2-I live in mid-southern California, it hardly rains.

3-ABS has almost gotten me into an accident before, I was in a lifted LR disco1 97, I turned out from a lane to avoid rear-ending someone, and almost did when the abs engaged and it took 40 feet to stop my vehicle from 45mph on dry asphalt.

4-I think ABS is bullsh!t, I think its nice for housewives that drive way too fast on the way to pilates, hopped up on lattes, in a large SUV, with no real driving skills. Its for people that panic behind the wheel and floor the brake pedal, I have been in 5 accidents, only one being my fault, so I am familiar with peoples reactions and can understand why ABS would be a good idea.
(please tell me if my opinion on this is skewed, I enjoy learning, and am not hard-headed)

5-I have lost work and over $1500 on this problem, and I have to drive 15 hrs to Washington state to try and make some cash before I take off to central america for the winter. I have to leave this friday, If i dont make it, my trip south might possibly not happen.

6-I have been put on the road 4 times, each time expecting the brakes to work, and have been EXTREMELY lucky that I have not got into an accident. (one time, last week, I lost brakes completely, and had to jump out of the van while it was going 5 mph through a busy intersection, i was trying to slow it down with my feet, luckily I was not killed) My vehicle is from Mass and was abused by a plumbing co before i acquired it, the body, and many parts are rusted to sh!t, including the emergency brake. I have learned the fine art of driving a vehicle many miles with absolutely no brakes, down shifting, throwing it into neutral and praying have become common place in my life.

7-One day, I will have money (hopefully) and will instal a proper ABS unit.

8-People have been driving without ABS for longer than with it, and there are many online (including me) who believe that ABS is actually more dangerous.
http://blog.sonicans.net/anti-lock-brakes/

Now that I am done with my rant, and hopefully have shed some light on my situation, I am asking for your help, if you do not agree with me, fine, let me know why, if you do on the other hand, PLEASE PLEASE PLEASE PLEASE help me! Hell, even if you dont agree with me, please help!

Here is the information I need:

*Any solid advice on why this is a bad idea.

*The specs for the brake lines, and fittings, coming out of the master cylinder, and in/out of the ABS unit . (I heard they were larger than the rest of them) Like if they are standard metric, etc and what sizes they are.

*If I should replace any of the brake lines, or if I can keep the existing ones. If I do have to replace, what kind of lines should i be looking at? Flexible ones? SS ones?

*I have found parts online that resemble what i need, mostly at classic cart parts stores, but they are all standard, and are made for older american cars. The abs unit has 4 lines coming vertically into the unit (two being the send from the master cylinder, and the other 2 going to one of the rear brake calipers), and two lines leaving horizontally towards the rear, which go to the front brake calipers. So the actual parts I need would be two t-block or 3-way fittings, and preferably would need the same basic configuration, two from top, one from the rear on each. If you can find something that would work, I would greatly appreciate it.

Thank you for reading all this, and if you have any feedback, that would be awesome.

crazyswede
10-17-2013, 03:47 PM
I have done all new pads and rotors and while my brakes work fine I can put the pedal to the floor with steady constant pressure. I have no external leaks but this is a pretty classic sign that the master seals are on their way out. Stomping on the pedal results in a firm pedal but gradual pressure results and a slow drop to the floor...the rapid stomp flares the seals so they work while slow but gradual pressure allow the fluid to slip past the seals. Its on my list of things to do...its a long list and while its a safety concern I keep an eye out for worsening symptoms and other things need my attention first.

shortshort
10-17-2013, 03:58 PM
I believe that gradual drop to the floor is completely normal. There has been a thread or two on it.

MillionMileSprinter
10-17-2013, 04:08 PM
**For all those who mentioned my idea of bypassing the abs system as being foolish and dangerous, here is my take on the situation, and please respond, I am a big boy and prefer honesty, if your perspective can elaborate more than just the potential danger to children, and my said guilt into the foreseeable future. Please, give me some data, or back your argument with science, preferably physics.


I don't think you *can* bypass the ABS system. It would cost you more in time and money to fool the ECM into thinking the ABS was functioning properly than it would to replace the ABS unit at $1800.
I think your only route is to repair the problem... whatever that turns out to be...
Sorry I can't give you more advice. :idunno:

crazyswede
10-17-2013, 04:13 PM
I believe that gradual drop to the floor is completely normal. There has been a thread or two on it.

I guess I better do some searching before I replace anything.

NetDoc
10-17-2013, 07:43 PM
Warped rotors can often cause a low brake pedal as well as fool the ABS into shunting when it shouldn't. Disc brakes self adjust by the caliper piston continually pushing further and further out from it's bore. The square cut piston seal provides a bit of release when the pedal is released, but any warpage in the rotors will push the piston back into it's bore. Instead of only having to travel a few thousandths of an inch, the piston now has to travel an eighth of an inch or more causing a low pedal.

So, in park, does the brake pedal "pump up"?

morerevsm3
10-18-2013, 06:54 AM
I improved mine (2002 316CDI) greatly by operating the ABS, then bleed it immediately. I drove the car in reverse fairly quickly on an unsealed road, and jumped on the brake pedal hard to activate ABS, did this ~ 8 times, parked, and put my pressure bleeder on the master cylinder and bled all 4 wheels, brakes now feel much better, unfortunately I now have a fuel leak at the front of the motor, probably hp pump which caused serpentine belt to come off and get chewed, now I need another pump

Boater
10-18-2013, 04:51 PM
Ilia - you mention several times bleeding the brakes at all 4 wheels, can you confirm when you, or any of the shops you have been to did the brake bleeding procedure, did they use the Mercedes diagnostic tool to activate ABS at the same time?

It seems to be hit and miss, but if you do not activate the ABS as you bleed the brakes you can be left with air in the ABS servos - some people get it out by luck not using the tool to activate ABS, but if you haven't used this procedure yet, do not throw any more money at it until you get to a dealer with the correct kit and who knows how to use it.

Seriously, when using the tool, you run a bleed program and it tells you which bleed screw to open when!

Another thing you can do without spending any money, unless you need to buy the equipment, is get a dial indicator on a magnetic base and set up on each disc in turn (wheel off), move it in so you get an indication and then rotate the disc through 360 degrees and note the variation in the reading. Got a feeling it should be within 0.02mm which is roughly 0.008". If your disk varies by more than this it will cause trouble with ABS (but might not cause a soft pedal) - often referred to as disk warp although disk manufacturers claim they have never had a disc returned warped even from race cars, instead you get random build ups of brake friction material or rust which make the surface uneven - it's just a technical detail, it causes exactly the same problem as a warp would! If your discs are within limits it may be possible to get them skimmed rather than replacing them - I have done this for myself, however my symptoms did not involve a soft pedal, the brakes were grabbing occasionally under light braking.

schwarzwaldsprinter
10-18-2013, 06:38 PM
Boater

Just a small correction, 0.02mm is about 0.001". 0.20mm is 0.008"

:cheers:

Sven


Ilia - you mention several times bleeding the brakes at all 4 wheels, can you confirm when you, or any of the shops you have been to did the brake bleeding procedure, did they use the Mercedes diagnostic tool to activate ABS at the same time?

It seems to be hit and miss, but if you do not activate the ABS as you bleed the brakes you can be left with air in the ABS servos - some people get it out by luck not using the tool to activate ABS, but if you haven't used this procedure yet, do not throw any more money at it until you get to a dealer with the correct kit and who knows how to use it.

Seriously, when using the tool, you run a bleed program and it tells you which bleed screw to open when!

Another thing you can do without spending any money, unless you need to buy the equipment, is get a dial indicator on a magnetic base and set up on each disc in turn (wheel off), move it in so you get an indication and then rotate the disc through 360 degrees and note the variation in the reading. Got a feeling it should be within 0.02mm which is roughly 0.008". If your disk varies by more than this it will cause trouble with ABS (but might not cause a soft pedal) - often referred to as disk warp although disk manufacturers claim they have never had a disc returned warped even from race cars, instead you get random build ups of brake friction material or rust which make the surface uneven - it's just a technical detail, it causes exactly the same problem as a warp would! If your discs are within limits it may be possible to get them skimmed rather than replacing them - I have done this for myself, however my symptoms did not involve a soft pedal, the brakes were grabbing occasionally under light braking.

Starpig
10-21-2013, 09:29 PM
Interesting thread, as it seems my sprinter, a 1999 312D, may have a similar brake problem. The car had this problem since I bought it. It failed its MOT due to a brake issue, and the previous owner replaced the master cylinder thinking that was the problem. He still could not sort it out and decided to sell the car. I was aware of the problem when I bought it though.

It seems that air gets into the brake system over time. There are no fluid leaks on my car either. If I bleed all 4 wheels properly then the brakes are good for a while. Then after some time the brakes turn weak. If I bleed again, the brakes are good for some time again. One funny thing about this is that I never saw a single bubble of air coming out when bleeding, and still the brakes get better for some time after bleeding. I don't even know if air is the problem, I only assume so because it gets better after bleeding...

I see to possible explanations to this. Either the ABS-unit is bad and lets air into the system over time, or there is air trapped in the system, maybe in the ABS-unit, that wont come out by conventional bleeding. Maybe the air only moves to a different place when bleeding and that's why the brakes get better for some time...?

I have tried pressure bleeding using a kit called "Eezybleed", putting 20 PSI pressure to the fluid reservoar, but the brakes were good only for a week or so after that. Next step i think will be to try reversed bleeding, forcing fluid from the calipers and up to the reservoar.

I have also heard of "extreme" bleeding done at the dealers using the diagnostic software to activate the ABS-unit. Would anyone know if it's possible to buy cloned diagnostic software and cable to use on a laptop?

Aqua Puttana
10-21-2013, 10:07 PM
...
I see two possible explanations to this. Either the ABS-unit is bad and lets air into the system over time, or there is air trapped in the system, maybe in the ABS-unit, that wont come out by conventional bleeding. Maybe the air only moves to a different place when bleeding and that's why the brakes get better for some time...?
The air being trapped is an interesting concept. I hadn't considered that posssibility. That said, if not the HCU/ABS unit then how does the air enter to be trapped?

The brake system air intrusion isn't a common complaint about Sprinters on this forum. The couple threads I recall reported as corrected were fine after the HCU/ABS unit was replaced.

...I have also heard of "extreme" bleeding done at the dealers using the diagnostic software to activate the ABS-unit. Would anyone know if it's possible to buy cloned diagnostic software and cable to use on a laptop?
It has been discussed here before. That type access is available on some level. I did a search from the blue bar above for you. Here's two hits which should help.

http://sprinter-source.com/forum/showthread.php?t=24011

http://sprinter-source.com/forum/showthread.php?t=21977

Duplicating the search will reveal more threads. My recollection is that member Owner is knowledgeable so his name is worth using in the advanced search.


Good luck. vic

crazyswede
10-21-2013, 10:34 PM
My rotors and pads are all new and not warped. What happens to me is I apply the brakes at lower speeds. .. the van sort of bucks or surges as if shifting up and down between gears. .. each time the van jumps forward a little and the brake pedal drops (actually the same feeling as a warped rotor. ) then when I am almost stopped the abs goes on.

I am fairly certain that this is due to a wheel speed sensor or tone wheel. I can also push the pedal to the floor with steady slow pressure van idling in neutral or park or any gear.

shortshort
10-22-2013, 02:17 PM
The abs/esp/mic/key bleed routine using DAD is for when a normal bleed does not solve the soft pedal issue. There is a recent thread on rear tone wheels being superseded by a newer, better part.

Boater
10-22-2013, 03:43 PM
Boater

Just a small correction, 0.02mm is about 0.001". 0.20mm is 0.008"

:cheers:

Sven

Fortunately I get the decimal places right when I'm working on my lathe!

Boater
10-22-2013, 04:14 PM
Interesting thread, as it seems my sprinter, a 1999 312D, may have a similar brake problem. The car had this problem since I bought it. It failed its MOT due to a brake issue, and the previous owner replaced the master cylinder thinking that was the problem. He still could not sort it out and decided to sell the car. I was aware of the problem when I bought it though.

It seems that air gets into the brake system over time. There are no fluid leaks on my car either. If I bleed all 4 wheels properly then the brakes are good for a while. Then after some time the brakes turn weak. If I bleed again, the brakes are good for some time again. One funny thing about this is that I never saw a single bubble of air coming out when bleeding, and still the brakes get better for some time after bleeding. I don't even know if air is the problem, I only assume so because it gets better after bleeding...

I see to possible explanations to this. Either the ABS-unit is bad and lets air into the system over time, or there is air trapped in the system, maybe in the ABS-unit, that wont come out by conventional bleeding. Maybe the air only moves to a different place when bleeding and that's why the brakes get better for some time...?

I have tried pressure bleeding using a kit called "Eezybleed", putting 20 PSI pressure to the fluid reservoar, but the brakes were good only for a week or so after that. Next step i think will be to try reversed bleeding, forcing fluid from the calipers and up to the reservoar.

I have also heard of "extreme" bleeding done at the dealers using the diagnostic software to activate the ABS-unit. Would anyone know if it's possible to buy cloned diagnostic software and cable to use on a laptop?

There is a chance the air is trapped in the ABS unit - if the valves are closed when you bleed the system no amount of pressure or reverse bleeding will shift the air because it is out of the circuit at that time, hence the need to activate ABS whilst bleeding.

Haynes has a reverse bleed procedure for something (clutch?) on the 312D, I tried it but found it a bit of a bugger to set up and ended up just using the eezybleed for that too. Something about connecting the hose to one bleed screw, pushing fluid through with the pedal, then sealing the end of the tube with your finger, wrigging underneath to the other bleed screw without letting go and connecting to it without letting air in..... maybe if you have an assistant and a lift? but jacked up (on axle stands) in the drive, very difficult!

Diagnostics tools for Mercedes are not as easy to find as other makes. You will see lots of Star multiplexers for sale but I doubt if you will find software to go with them, and you may find you need to buy a special lead for the sprinter (14 pin round socket?). There are expensive professional tools, the closest to being affordable for DIY is carsoft but I haven't heard how their reputation is for a while - there were some rumours of customer service issues and difficulty getting laptops to talk to the multiplexers properly. I have used an old version of carsoft and it had ABS bleed function, but I was not sure if it worked or not - I couldn't hear the pump, and the van didn't pass it's MOT (although it didn't fail for brakes) and has not been on the road since....

Realistically you need a dealer or a properly equipped independant garage to try bleeding it - I can't even guess the price, or what they might decide is wrong with it.

Boater
10-22-2013, 04:28 PM
My rotors and pads are all new and not warped. What happens to me is I apply the brakes at lower speeds. .. the van sort of bucks or surges as if shifting up and down between gears. .. each time the van jumps forward a little and the brake pedal drops (actually the same feeling as a warped rotor. ) then when I am almost stopped the abs goes on.

I am fairly certain that this is due to a wheel speed sensor or tone wheel. I can also push the pedal to the floor with steady slow pressure van idling in neutral or park or any gear.

I agree, that reads like tone rings symptoms.

When the engine is running the booster/servo should help you push the pedal down, with the engine off and the vacuum exhausted (takes a few pushes of the pedal) the pedal should hold steady.

I went through a lot of messing with the servo and master cylinder on my car before I discovered the tone rings were rusted through and cracked, the new tone rings cured it.

Starpig
10-22-2013, 05:21 PM
The air being trapped is an interesting concept. I hadn't considered that posssibility. That said, if not the HCU/ABS unit then how does the air enter to be trapped?


Maybe air was not the initial cause for doing brake work, like fitting a new master cylinder.

From what i've heard these cars are known for having a low brake pedal, and this is usually regarded normal, as long as the brakes otherwise have a good function. (correct me if I'm wrong)

Maybe some unexperienced tester failed the car on the inspection due to a low pedal. Then if a new master is fitted air gets into the ABS-unit and is trapped. Just a theory...

Starpig
10-22-2013, 05:49 PM
There is a chance the air is trapped in the ABS unit - if the valves are closed when you bleed the system no amount of pressure or reverse bleeding will shift the air because it is out of the circuit at that time, hence the need to activate ABS whilst bleeding


Could it be possible to somehow make the valves in the ABS-unit stay open during bleeding? Like disconnecting the cable and putting voltage to the correct terminals (if you are able to figure out which ones)?