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Matt
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22002
Experience:  BEng hons Mech engineering, in auto industry 22 years
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2013 sprinter 313 i herd a ssing under load , took to garage

Resolved Question:

2013 sprinter 313
i herd a hissing under load , took to garage they changed air mass sensor.
still hissing 2k + revs loss of power under load
another garage checked fully (£150)!. No leaks found and say it is the inlet manifold !
and is a common problem. the van has only done 60k miles.
these new sprinters are crap it is problem after problem and the parts are made of gold.
should i take the van to a dealer to make sure
thanks
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
The loss of power is i think when the turbo kicks in, engine revs again to 4k when air mass sensor changed but
just struggles when loaded after 2k revs. when stood still can not really hear any hissing even at 4k revs
Expert:  Matt replied 1 year ago.

Hello

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattenedpiece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Expert:  Matt replied 1 year ago.

Hi

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