fading brake pedal

mailtome

New member
Has anyone experienced a brake pedal that goes all the way to the floor. There are no external leaks or low levels in the reservoir. Reference vehicle is a 2003 Sprinter van 2500.
 

Altered Sprinter

Happy Little Vegemite
Has anyone experienced a brake pedal that goes all the way to the floor. There are no external leaks or low levels in the reservoir. Reference vehicle is a 2003 Sprinter van 2500.
Interesting point it may be the master cylinder, But have you replaced brake pads front and rear with aftermarket pads! Without the sensors?
This will totaly confuse the brake system as the electronics are known to fail because of this , in effect soft brakes yes they can go to the floor the sensors were designed to equalise brake pressure as it's part of the ESP control system, I can not explain in exact detail as to why, but that computerized brain box shuts down if all is not well , a few guys down under in my state did this and lost brakes as a result of not puting in genuine Mercedes parts with the sensors, they are meant to be replaced both pads and sensors as they wear down.
Richard
 

Zach Woods

New member
Hello mailtome -

Did your brake pedal go all the way to the floor while driving (vehicle in motion) and trying to stop or when stopped?

If when stopped, how long had the engine been running for when the brake pedal went all the way to the floor?

If in motion, was there any brake force available or was there none available?

What were the circumstances that lead to brake force/ brake pedal not going all the way to the floor returning? (ie, car in motion, engine rev's going up, a visit to a mechanic, etc.)

Thanks,
 

mailtome

New member
Did brake pedal go all the way to the floor while driving ... or stopped?
If stopped, how long had the engine been running...? If in motion, was there any brake force available...?
What were the circumstances... ?
SORRY for my delayed response... computer drive failure :(

Front brakes were replaced by "German Master Tech" (not dealer) prior to noticing problem. Do not know details re: Original Equipment pads/sensor (THANKS Richard!!!) but will investigate.

Pedal slowly goes to floor when vehicle stopped, applying hard force; pedal goes down easier if vehicle was only recently started. Braking while in motion seems normal (though maybe it does start to grab a little lower).

THANKS!
 

Altered Sprinter

Happy Little Vegemite
Brake fluid may be low this will cause brake fadeout or in some situations Failure.
It may be a slow vacuum leak, the list goes on! Question you replaced front brakes! But were the senors replaced as well or did they put back the old ones? or if replaced with new after market ones without sensors and the original ones in the rear are sensor-ized ... then you have two braking pressures working against each other, If the front ones are taking all the forces because of rear not working that well, the front pads can overheat under extreme pressures, and thus fade out will become evident under different operating conditions.
Towing trailers has the same effect as the front brakes take the most loading effect under stopping conditions as the rear trailer tends to push the forward vehicle under it's own motion:rant:.
Check em' out
life's too short :thumbup:
Richard
 

Zach Woods

New member
Howdy mailtome -

Couple of quick thoughts:

1. Diesel engines do not have as much / as convenient spare vacuum as gas engines do. This can mean that brake assist is limited or not available under some driving conditions (typically when vehicle stopped only just started). I am no more than a "shade-tree" mechanic so I could have the above wrong (but it is what I have heard / learned) and I am willing to hear corrections from others.

2. I have heard other Sprinter owners mention that the brake pedal can go right to the floor with feeling of little or not pressure when the vehicle is stopped but even when the engine is running. I have yet to experience this but I trust the folks that I have heard describe this circumstance. Their vehicles have nothing wrong with them and brakes have functioned fine other than this symptom.

Zach
 

Thunderbolt

New member
One of the reasons I got a sprinter was that a friend has one and I was really impressed with it. I never thought that I could afford one, but one came up at the right spec and I got a loan:thumbup:
One of the things he told me was that the brakes go down a long way but always stop you.
I am going to investigate further.
 

rvdriverca

New member
you must replace the brake fued every 2 years, as mosture gets in, under hard braking the heat changes the mosture to steam. This causes the brake pedal to go down to the floor as gas can be compressed. I have run this one my self
 

chaozz

New member
Willing to bet the master is bad.
if I'm correct the sensor's on the front are
just wear indicator and all the do is once they
hit the router they ground out causing the light to come
on..

one thing that can happen when people do the brakes
if they just push the caliper pistons in with out cracking
the bleeder on each caliper is it can screw up the ABS system
the fluid is forced to fast back into the system and the setiment thats
in the calipers can clog the little ABS ports.
when this happens its very very expensive since the whole ABS
unit has to be replaced.

If you want to do your own master cylinder let me know i can
explain what to do its pretty easy ..just need 2 people.
 

WB118

Active member
I replaced the master cylinder and booster, still spongy pedal
Keep in mind, the post indicating a possible master cylinder, that you quoted, was in response to a symptom where the pedal went all the way to the floor. You have a “spongy” pedal which may be entirely normal for a t1N van, unlike most other cars. The pedal never has a hard feel, but still stops the vehicle very well. If your pedal feels “soft” but stops the van easily and consistently even though the pedal travel seems long, your system is likely normal. This assumes the lines and master cylinder have all been bled correctly.
 

KTMJack

Winnebago Sprinter
I have the same problem I am the second owner and the person I bought it said it has been this way since new
I have to pump up the brakes to get a better peddle .
We also have a new Ford Ranger and the peddle would go to the floor brand new 3 Stealerships cannot fix it :thumbdown: They kept bleeding the brakes That
was not fixing the problem. This is in the ABS So what I did was find a dirt road and slam on the brakes so the ABS would buzz your foot a couple times All better now Let the ABS do the bleeding
 
My 2003 had this issue with no leaks and new master cylinder. It turned out I had a leak at the input shaft of ABS pump motor. Seal was bad. I have since heard of multiple other people whose sinking pedal was fixed by replacing abs pump. I hadn't seen it in shops but seems to occur on these sprinters. Posted is a picture of the seal after autopsy.
I hear people mention the booster in this context but it would have to be explained to me because the brake pedal pushrod rod ends in a cup built into diaphragms. On the other side the master cylinder pushrod seats in this cup. Metal to metal, so I don't understand what could be "sinking" before the hydraulic part of the system, especially having never seen a "soft pedal" booster fail in shops
IMG_20230324_150002_696.jpg
 

bill in tomahawk

Active member
Before you condemn anything try doing10 panic stops to see if that generally stabilizes your stopping/braking pedal behavior.

It's an old trick and it help me after a brake system rebuild.

Bill
 

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