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Sprinter Brake pedal falls away or soft

Do you have a Sprinter with soft pedal or the brake pedal falls away almost to the floor? Three things you need to check or do. 1. If you have just changed brakes or opened the system to air you may need to bleed the brakes. You can do this the old fashioned way pump, hold, crack the line or the preferred way would be to do what Daimler calls the Exceptional bleeding. This is done using a Daimler scan tool at your dealer.
2. Check the vaccum. You should have 20 to 22 HG at the booster, if the pump is pulling too much the booster actually will pull the pedal away from you. Also inspect the check valve at the booster. I have seen these cracked also.
3. If the vaccum is ok your problem is most likely in the booster.
4. Dont let a dealer talk you into changing the ABS control valve for $2k that will not fix your problem.
5. We are assuming you have inspected the master cylinder for internal bubbles.

Hope this helps.

Roy
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Comments

  • Hello! This is exactly the symptoms i am experiencing with 2005 sprinter 2500. I am an independent shop owner that thought I was pretty clever until this problem came up! lol I am getting 28HG vacuum at the booster. Is this the excessive level of vacuum that you are referring to? Could this be causing the "pedal fading" problem i am having. I have replaced master cyl. and (unfortunatekly I think) the ABS unit. I have bled the system numerous times. When i remove the vacuum from the booster, the pedal does not fade. As soon as I reconnect it, the pedal begins to fade. Any help with this would be unbelievably appreciated! Thank you Ken
  • Give me a couple days, I have another Sprinter here doing the same thing and the booster did not fix the problem. I have our Daimler rep. coming out to help with this thing. They are thinking they have a bad run of boosters. I will reply as soon as possible with the fix.

    Roy
  • THANKS FOR FAST REPLY!! I EAGERLY AWAIT........
  • Goog Morning! Ken here again. Just tried another test that may help.....it appears that vacuum pump is "weak"? when we put a guage on it and pump/depress brake pedal...vacuum pump drops to around 5HG. then as pedal is held down...and is fading of course....the pump SLOWLY builds up pressure to approx 20HG. before this test, vacuum to booster is 26-28HG. Is it therefore possibly the vacuum pump that is causing the problem? Ken
  • Hi Ken, I also found the same thing on my problem truck. I had another 2005 in the shop and decided to swap vacuum pumps with a known good one. I did this and have the same problem, no changes with a different pump. While doing that I moved the vacuum check valve and tube over since it was easy. No change. The Daimler rep I talked with this morning tells me that this is a European booster and will fade to the floor. I told him that's crap because I have another 2005 right next to it with a nice solid pedal. He did mention that after doing the exceptional bleed process using the Daimler diagnostic tool you need to do a manual bleed also. Maybe these trucks really trap air in the ABS Valve or Master cylinder. Did your truck have anything on the brake system changed prior to this problem happening? Now they (Daimler) is thinking I have a faulty new part somewhere. I doubt that but I am running out of ideas on this one also.

    Roy
  • Hello No brake work was done previous to this happening. Tried reducing vacuum to 20HG - made no difference. eagerly awaiting any further news/diagnosis on this problem. Many thanks for your time on this.... Ken
  • Ken,

    I'm convinced it is not a problem with anything in the engine compartment. In an effort to isolate this thing after much testing we have brought in a known good 2005 with great brake pedal and moved the following parts from the known good unit to the bad one with no luck.

    1. Vacuum pump
    2. Vacuum booster
    3. Vacuum check valve and hose
    4. Master cylinder
    5. ABS control valve
    6. Bled multiple times

    It has to be something in the base brake system which from the ABS valve back consists of nothing more than hard brake lines, rubber lines and calipers. The rubber lines have been physically inspected while brakes are being applied and they are not expanding at all. The last Daimler rep I spoke to Friday said he had seen this problem and it was a stuck caliper piston that was cocking in the housing and was not applying consistent pressure on the pads giving the pedal feel we are experiencing. We will be going into the calipers tomorrow. How many miles are on your unit? This one has 221,000. Maybe removing the calipers and seating the pistons with C clamps then testing pedal feel with the clamps in place to see if the pedal still falls would isolate the base brake system. At least it would take the wheel ends out of the picture. After that I think we will just burn it.
  • Ken,

    Take a rubber tipped blow gun and blow air backwards into the closed bleeder screws. I found one that was not leaking fluid externally but may be sucking air in. It would blow bubbles when air was applied. I will know more tomorrow when I get parts. Mine was right front.

    Roy
  • Thanx again for your reply. Will try the air blower test tomorrow. Otherwise nothing to add. Another mechanic friend of mine (ASE Master Tech) has the same vehicle in his shop about 25 miles away....and it is doing exactly the same thing!!! Something is a bit weird here.....Does Daimler admit to this happening with any other vehicles? It stretched credulity to believe that our three vehicles are the only ones with this problem!!! Awaiting your reply....Ken
    P.S. Am having a problem with "high idle" function. Switch seems to have power to it (background light comes on) but no high idle. We observed a very light "thud" noise when turning the switch off after unsucessfully going into high idle....but now we don't hear anything when we turn it off. In trying to trace this "high idle" problem, AllData refers to a "Fuse Block 3" where fuse is located for this operation...But nowhere does it twell us where the heck "Fuse Block 3" is located!! Any help you can offer? Thanx again...Ken
  • Not sure the bleeder thing is our issue, One of mine had some trash on the seat of the bleeder causing a slight leak. After cleaning the air leak went away but our main problem did not change. Daimler is going to send a rep to my shop to get to the bottom of this issue.

    The Sprinter manual says fuse block 2 & 3 are under the seat. Fuse block 1 is under the steering column. We do not have this feature on our units, sorry I cant be more help. The high idle connector pinouts are as follows:
    Cavity 1 = gy/dg/rd Lamp driver
    Cavity 3 = br/wt High idle on signal
    Cavity 4 = br/wt High idle on signal
    Cavity 7 = br Ground
    Cavity 9 = bk/rd Fused optional equipment relay output

    Hope this helps,

    Roy
  • More on the high idle switch:

    check the fuse 12 - 15 amp at fuse block 3
    Check optional equip. fuse at battery dist. block hanging off the pos. post. should be fuse 2
    send me a fax number and I will fax you a wiring diagram for it.

    Things in this circuit:
    1. Optional equipment relay
    2. Fuse block 3
    3. ECM
    4. Daytime running lamps relay
    5. High idle switch
  • Ken,

    I found my brake problem on this unit. The rear brake pads were worn at an angle. It seems the vendor that did the rear brakes for us a month or so ago left the springs off the outside of the calipers. The calipers were caulking sideways when applied and wearing the pads crooked. We noticed the springs missing when we did a PM on this truck and it seems the problem started shortly after the springs were reinstalled. I am assuming the pads after being worn crooked would caulk a little in the caliper when the brakes were applied and caused soft braking and a pedal that would continue to fall as the pad was continuously caulked sideways under increasing pressure. Check all your brake pads and caliper springs. New pads fixed the soft falling pedal problem.

    Roy
  • Ken,

    Did you find your brake issue?

    Roy
  • Ken,

    Any luck with your brake problem?

    Roy
  • bspertybsperty Posts: 20
    Does the sprinter whip antenna work properly on American aftermarket radios.
    I know it is a powered antenna.
  • bigjay3bigjay3 Posts: 8
    Hi Guys, Im 87 years opld, a master mechanic, federal aitcraft/engine mech, thers nothing I dont know about brakes. I have a great west motor home diesel Freighliner turbo sprinter. Vehicle was at Freighliner dealer for two months, they replaced booster with master cylinder, rotors, ABS module,$2800,vacuum pipe to pump, power bleed system, all accomplised with factory rep, final result, they could not cure it, reinstalled all my old parts and said get it the hell out of here, (NO CHARGE). Since then I have replace master cyl several times, I n an effort to cure I disconnected the ABS, lots af plumbing, attached 2 front brake lines direct to rear port on master cylinder, two rear to front port, made a small resorior to keep abs filled with fluid. Made plugs to seal brake ports on abs. WELL same old crap pedal goes to floor, Im going to make one more test and connect all 4 wheels direct to rear port on master??????? THERE IS NO DOUBT THAT THE MASTER CYLINER IS MANUFACTURTED DEFECTIVE, YET BOSCH WILL NOT ADMIT, i HOPE SOMEONE WILL START A CLASS ACTION SUITE AGAINST THIS. IF YOU THINK YOU KNOW MORE THAT i DO PLEASE ADVISE. i HAVE AN $80,000 MOTOR HOME THAT iM AFRID TO DRIVE, SO FAR iVE ALL OVER THE COUNTRY, 24,000 MILES AND i HOLD MY BREATH EVERY TIME i GO DOWN A HILL, RESPECTFULLY YOURS,,,BIG JOHN
  • bspertybsperty Posts: 20
    Big Jay, My sprinter has been doing it since 26,000 miles i now have 160,000.
    IT NEVER WAS FIXEd AFETR MANY ATTEMPTS.
    Mine is heat related as it only happens in the summer when temps get above 75 or so. It almost killed me once as the ABS was not working and my brakes locked up on a wet road THANK GOD there was a median i could steer off into.
    If the president at FREIGHTLINER HAD ANY BALLS he would contact me. I think i will go on an internet attack and tell the truth.There is an old saying." The truth Hurts."
  • John,

    Have you ever lost one of the brake springs on the rear calipers, found it missing and then replaced it without replacing the brake pads? I had one with a brake fade issue where the pedal would go to the floor. Ended up being tapered brake pads. The outer spring that keeps the caliper centered was lost on road and discovered missing while performing a PM inspection. We replaced the spring without replacing the pads as they were more than 75%. With the new spring installed again this held the caliper back in the proper position which now created a slight gap between the rotor and pad on one edge of the pad. When the brakes were applied now one edge of the pad would hit the rotor first and then due to the tapper in the pad the caliper would twist a bit before the other side of the pad would hit the rotor. This slight gap at the pad and rotor translated into almost a full stroke of the brake pedal in the cab. Driving with the spring missing created a scenario where the caliper would twist a bit when the brakes were applied which in turn wore the brake pads in such a manner that a slight tapper was created on the pads themselves. Replaced the pads with new and the pedal fade issue went away. Hope this helps. Roy
  • bigjay3bigjay3 Posts: 8

    Hi Guys, this is big john, master mech my whole life, also federal aircraft & engine mech LIC1244403, PLEASE PLEASE listen to what I have discovered over the last 8 years with my sprinter 2500, Above you read my message with the dealer and factory rep, right now im running without the ABS, master dirct to wheels, remember every thing was replaced at dealer, I mean everything, boster, master, rotors, ABS ect, this is what I have come up with, First ooof all DO cut the rotors, first problem is rotors are too thin (NEW) they expand and contract, in the morning I have little or no brakes, pump 3 or four times and I have good pedal about 3/4 but as I start down the street vehicles feels like it will not stop, I ride the brake a little and then Im fine, have very good pedal and nice and sentisitive, away we go, great brakes as long as im in the city, now after drining on the highway for 10 or fifteen minutes pedal goes almost to ffflfoor but I stop OK, now I use my brake every 5 minutes to keep pedal up, I say the totors are the problem but theres nothing you can do about that, PS Ive had a prussur bleed since 1948, really works great. OPPS above DO NOT CUT THE ROTORS I hope Ive been of some help to you guys and if any one finds a cure Im willing to spent $5000 to have brakes same as my car. BIG JOHN

  • bigjay3bigjay3 Posts: 8

    I hope my message was accepted big john

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