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Mein Sprinter
12-23-2013, 04:45 PM
Newbie here.

Acquired a 2010 Roadtrek SS Agile Camper.

Don't take me to Roadtrek-it's a Sprinter neverthless. There is a soft slight "clunk" feel when taking off from a stop but does not do the same when slowly rolling and taking off. Any ideas? It only has 8080 miles for a 2010 model! Warranty will cease this coming April :cry:

cheers...

dynaco1
12-24-2013, 03:50 AM
Could be one of the rear calipers is slow to release after letting off the brakes.

FireandIceHVAC
12-24-2013, 12:44 PM
It's the start off assist feature. It's normal. Mine has been doing since new

Mein Sprinter
12-24-2013, 07:11 PM
It's the start off assist feature. It's normal. Mine has been doing since new

Thank you for chimming in. Excuse my ignorance, what is the assist feature.

cheers...

Mein Sprinter
12-24-2013, 07:14 PM
Could be one of the rear calipers is slow to release after letting off the brakes.

Thank you...I'll have to take it to MB for some diagnosis. Still under warranty till April 2014. :frown:

cheers..

FireandIceHVAC
12-25-2013, 10:01 PM
Thank you for chimming in. Excuse my ignorance, what is the assist feature.

cheers...

http://www2.mercedes-benz.co.uk/content/unitedkingdom/mpc/mpc_unitedkingdom_website/en/home_mpc/van/home/new_vans/models/sprinter/sprinter/facts/overview/comfort.0003.html

sailquik
12-25-2013, 10:23 PM
Mein Sprinter,
Not sure that the Start-Off Assist (SOA) feature is your problem unless your Sprinter only makes the soft "clunk" when you are on an uphill grade of > 4%.
Don't think the SOA feature deploys until the angle sensor detects an uphill grade of 4% or more.
Could be, but I've had several NCV3 with Start Off Assistance and have never noticed anything beyond it does not roll back is you ease the brakes off to get underway.
Here's the MB technical description:

"After the brake pedal is released, the brake pressure is maintained for approx. two seconds, allowing you to switch your foot from the brake pedal to the accelerator without having to worry about the vehicle starting to roll. Start-Off Assist is activated on uphill slopes of approx. 4% or steeper. It is not activated when moving off on the flat or on a downhill slope."

Might be good to take it in to an authorized Mercedes Benz Sprinter Commercial dealer and have them run the diagnostics and also check the SOA feature while you are still under warranty!
Hope this helps,
Roger

nash
12-27-2013, 02:28 PM
I have the same "soft clunk" when I accelerate from a stop. Happens on all surfaces; level, forward or rear incline.

dynaco1
12-28-2013, 12:51 PM
My 2014 has been making that sound since new. Could it be diesel fuel slapping the fuel tank?

Dimitri
12-28-2013, 06:03 PM
I have the same "soft clunk" when I accelerate from a stop. Happens on all surfaces; level, forward or rear incline.

I have 2011 2500 and i get the same clunk...correct all surfaces.

sailquik
12-28-2013, 06:54 PM
Are you sure the "soft clunk" is not simply the brake pads releasing from the disc?
The 2014 4 cylinder 7 speeds idle a bit faster (760 RPM vs 680 RPM for all previous Sprinters (T1N OM-612/OM-647 and NCV3 OM-642 V6's).
I noticed this morning that my 2014 does have a noise that could be interpreted as a "soft clunk" when I release the brakes.
Best way to hear this is to ease off the brake pedal, and the brake pads will "chatter", then add a slight pressure to the brake pedal until the brakes lock up again.
You will hear a "soft clunk" when the brakes lock up (and the shuddering from the engine/trans will stop).
Then release the brakes and start to drive off.
I'll bet you hear the same "soft clunk" when the brake pads release that you hear when they lock up.
Again, you can test this by easing your brake pedal with the Sprinter in gear (it will be 1st gear....you have no choices on this as the trans will always shift to 1st gear when the brakes lock up at traffic lights/stop signs anytime the wheels stop rolling completely) then slightly release the brake pressure until the brake pads "chatter" (almost a groaning sound) on the discs.
Then increase the pressure slightly until the wheels stop rolling.....you will hear a slight "soft clunk".
Then release the brakes completely as if you are going to drive off.
I think you may agree that the "soft clunk" when the wheels stop rolling because the brake pads have stopped them from rotating is pretty much identical to the "soft clunk" when they release for you to drive off.
My guess would be that the brake pads make the "soft clunk" when they stop the disc rotation and when they release the disc so it can again rotate.
This is most likely completely normal as there has to be some slight clearance around the brake pads so the disc brake pistons can move them into engagement with the brake rotors. Also it could be clearance in the brake caliper "sliders". All of these assemblies have to have a little clearance or they would seize up too often.
Hope this helps,
Roger