Spongy brakes

[sonny]

On my Mercedes sprinter the with the engine running the brake pedal slowly goes down to the floor I can pump it up a few times and still goes to the floor if the engine is not running the brakes are firm . Any ideas what the problem might be .Thanks

 

[Swifter]

Sounds like air in the brake system .need to bleed it .

 

[Garfields]

Amusing you are not loosing brake flued I would be looking at the brake servo
If the peddle is staying hard when the engine is off it's unlikely to be hydraulics that are letting flued pass

 

[dunnah01]

The brake master cylinder seals sound like they are failing.

 

[tonyidle]

Do you mean the pedal literally goes to the floor? Or just much softer (which is normal)?

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[sonny]

To the floor slowly.and not losing any fluid

 

[poppycamper]

Funny you should mention this... I had exact same on my Movano which I mentioned to my local Indy garage.
Anyway he has a Sprinter PVC which does the exact same.
His theory was that because moho is constantly heavy and requires heavier braking to stop van it is possible to cook and degrade the brake fluid.
I obviously had my doubts but he convinced me that changing fluid (as he regularly does to his Sprinter) would sort issue out.
Guess what... it did... brakes back to being as they should be.

 

[dunnah01]

To the floor slowly.and not losing any fluid

Can you still get it to the floor with a lot of extra effort when engine is not running

 

[SM0129]

Sounds like servo is at fault

 

[Jake vE]

I have a MK1 sprinter Hymer and suffered similar problems. Brake fluid change did help and passed a brake test. They are still a bit like standing in mud but it seems this is 'normal' for my age of sprinter

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[sonny]

Can you still get it to the floor with a lot of extra effort when engine is not running

No

 

[eurajohn]

Check post #7 on this site Here
Not an uncommon problem and probably none of the previous suggestions

 

[sonny]

I have a MK1 sprinter Hymer and suffered similar problems. Brake fluid change did help and passed a brake test. They are still a bit like standing in mud but it seems this is 'normal' for my age of sprinter

My sprinter is 2003 54000 miles only done 20 miles last 3years virtually no rust sweet engine but as you know standing around doesn’t help.
Just wondering how to isolate the servo for testing

 

[sonny]

PI have a MK1 sprinter Hymer and suffered similar problems. Brake fluid change did help and passed a brake test. They are still a bit like standing in mud but it seems this is 'normal' for my age of sprinter

My sprinter

Check post #7 on this site Here
Not an uncommon problem and probably none of the previous suggestions

thanks for that

 

[ctc]

Mine does the same, Mercedes said its normal.

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[Landy Andy]

My sprinter is 2003 54000 miles only done 20 miles last 3years virtually no rust sweet engine but as you know standing around doesn’t help.
Just wondering how to isolate the servo for testing

Test a brake servo by pressing the pedal many times until the pedal is hard, and high up, then start engine and brake pedal should fall. That shows brake servo is working.

 

[mitzimad]

Read this from the gov MOT advice page............

Vehicles with petrol engines uses the inlet manifold to generate the vacuum for servo assistance.
Larger vehicles such as vans and 4x4s with diesel engines usually use a pump to generate the vacuum, Unlike the inlet manifold of a petrol engine, there is no vacuum relief with a pump. If excessive pedal pressure is applied when the vehicle is stationary (and the engine is running) as required for the MOT test the hydraulic pressure required to stop the vehicle will be grossly exceeded and fluid will be forced past seals that are between circuits.

The rare occurrence is known as diesel creep; and it is often incorrectly diagnosed as being caused by a faulty master cylinder.

The solution is to stop applying the excessive pressure.

If you can get the brake pedal to creep with the engine switched off and servo exhausted,
or actually under braking there is a serious problem that requires urgent attention!

A road test maybe an option to satisfy yourself, but if in doubt give the benefit of the doubt to the vehicle presenter.

 

[ambulancekidd]

This was a reported problem on our Sprinter ambulances, but after much research they were pronounced to be within normal range.
I certainly didn't hear of a brake failure in any of our huge fleet & just got used to it.

 

[joka250]

Funny you should mention this... I had exact same on my Movano which I mentioned to my local Indy garage.
Anyway he has a Sprinter PVC which does the exact same.
His theory was that because moho is constantly heavy and requires heavier braking to stop van it is possible to cook and degrade the brake fluid.
I obviously had my doubts but he convinced me that changing fluid (as he regularly does to his Sprinter) would sort issue out.
Guess what... it did... brakes back to being as they should be.

Always a good place to start. Good advice.