Vacuum noise

Hi all Just returned from a 4000 kl road trip our Sprinter performed extremely well in many varied road conditions and the Winnebago section was also a great success .average fuel 15.2 ltrs per 100 k
The only thing I noticed was a noise from the engine compartment that I describe as a vacuum noise ( short gasps of sucking air )it's not regular but I hear it when the brake is applied while at traffic lights for example.
The noise is obviously from the vacuum system but I am unsure if this should be heard or if I might have a leak that I need to trace , any suggestions ?
:thumbup:
 
Hi all Just returned from a 4000 kl road trip our Sprinter performed extremely well in many varied road conditions and the Winnebago section was also a great success .average fuel 15.2 ltrs per 100 k
:thumbup:

Off topic Pierre but your fuel figures amaze me. I'm running a T1N 313 long and tall with a full motorhome conversion and tow a trailer (about 1 tonne), on a recent trip to Queensland return, about the same distance as you, my fuel figures were just over 10lts/100kms. Short trips around home without the trailer I regularly get roughly around 9.2lts/100kms.

Rob.
 
Hi Rob our rig is 3.5 high weighs in at 4.5 t loaded and quite a bit wider than yours.
I agree that the fuel use is high it varies a lot , can be as low as 12 ltrs or as high as 17.5 it depends on the terrain but mostly the wind all suggestions on how to improve our economy will be gratefully received. :thumbup:
 

sailquik

Well-known member
Pierre,
Sounds like you have a major vacuum leak. Check all the vacuum lines that lead away from the vacuum pump on the front of your engine.
Since it's a big and loud sound, it could be one of the larger vac lines that go to the brake booster.
Not having full vacuum in your brake booster could be unsafe.
If it's just a slow leak off of the vacuum in the booster canister when you shut the engine off, that's pretty normal, but it sounds like you have something larger going on.
As far as getting better mileage, do you have a Scan Gauge II (or similar) so you can regulate the % of engine LOAD.
Perhaps you may not understand the MB engine management systems.
You can be chugging along at ~<2400 RPMS in top gear (which transmission do you have...the NAG-1 5 speed auto like in the USA or something different) which is an overdrive gear, and be using the maximum amount of fuel and packing in the maximum amount of turbocharger boost.......and you will never know it.
A simple manual downshift, into a more powerful gear, will bring your RPMs up into the range where your Sprinter makes it's best and most efficient power and your fuel consumption and boost rates will drop significantly.
The Scan Gauge II (or similar) helps a lot as it will tell you what your current % engine LOAD is, and you can make conscious decisions on things you can do to reduce the % LOD....which can reduce your fuel consumption.
Manually selected lower gear ratios, higher RPMS DO NOT result in more fuel usage in a Sprinter with the MB engine management systems as the fueling rate and turbo boost rates are completely under the control of the engine management systems....NOT under the control of the driver.
The driver simply has the ability to tell the engine management systems that you want More power.....maintain your current power.... or less power!
More power means the fueling rate goes up...often to the max, in a heavily loaded (and wind loaded) RV.
Maintaining your power means the engine management system will adjust everything to keep you going the same speed....and... if anything changes (like more wind or an uphill grade) it will add more fuel and boost to maintain the current speed.....UP TO the absolute MAX.
Less power tells the engine management systems to reduce the fuel flow to 0.000 GPH/LPH.
When the %LOD on a Scan Gauge II reads 0%..... there is no fuel going into the Sprinters engine at all. You are just coasting along.
So, in summary, the driver has no way of knowing what the % LOD currently is, and therefore has no way to really control the amount of fuel used. With the SGII you can see, in real time, what your engine management systems are doing, and make changes to improve your fuel consumption figures.
Roger
 
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Re the vacuum noise I went over the vacuum lines today and sprayed shaving foam on as many joints as I could with no leaks found , I listened carefully and the noise seems to be coming from around the footwell under the steering wheel I isolated the brake booster from the vacuum line but left the engine running and could still hear a regular noise when I had my head down near the foot well . The best I can describe it as regular ( about 5 second apart ) short sharp suction noise it can be heard while in the cabin but not over the engine when listening under the bonnet

Re the Scangauge can these be fitted to 413 CDI successfully I went to the Australian web site and sprinters are not listed???
Thank Roger for the comprehensive reply you are correct in that I don't understand how a MB engine works but I'm learning thanks to people like you on the forum.:thumbup:
 

Altered Sprinter

Happy Little Vegemite
Check for carbon leak at the joint at the back of the turbo.
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check filter box has no dirt/ dust blockages
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When you clock in 900k's plus on 74 liters.3.5 metric tonne loaded '...well have a great day.
Cheers Richard
 

sailquik

Well-known member
Pierre,
It's my understanding that you would need to buy an adapter for the normal ScanGauge II OBDII interface connector, but that the adapters are available in AUS.
Your AUS spec. Sprinter has a different OBDII port configuration that needs the adapter to connect properly.
Someone just recently reported that he had been able to get the SGII to work quite well.
You are most welcome on the "How Sprinter engine management works".
It seems important to me to convey that Sprinter drivers really have not been provided any way to tell how hard their Sprinter is working by Mercedes Benz, and it's important to know if you want the most trouble free kilometers with better fuel mileage.
Roger
 

NORTON

Member
Pierre, If you have access to the 05 service manual look in group 11 page 6, it describes the operation of the vacuum circuit, perhaps the noise is coming from the vacuum line air filter which in the area you described. murray
 

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