Air leak engine light - but there is no leak!

[Brian Kenny]

Hello all,

I have a 2013 c250 with 45000 miles. There is an unusual problem with an engine light. Step by step below
1. Air leak engine light
2. Brought to MB garage and there was a slit in the turbo pipe, fixed
3. 1 hour after the light came back
4. Back to MB and carried out further testing, mechanically perfect, software was updated
5. 1 hour later the light is back on
6. Brought for second opinion and there were 2 fault codes raised P227906 (air leak - algorithm) and P040200 (flow in egr cylinder bank 1 is too high) . This mechanic had the car for 7 days and on the 7th day got an egr fault, as well as air leak. He advised what MB garage done should have fixed the problem. Egr fault never raised before

sometimes there is an odd smell of exhaust fumes but it's very rare.

Did anyone else have an issue like this? Possible cause and fix?

Would EGR replacement fix it as maybe the exhaust gas pressure is forcing a back pressure on the intake fooling the system into a leak? Thanks

 

[LostKiwi]

I'd certainly be looking at the EGR. If it's sticking open it would effectively be a leak in the inlet tract and you also have a code showing the flow rate is too high.

 

[Brian Kenny]

Just got it back from mercMerc after 2 weeks, turns out the air flow sensor was bad. No faults etc for the sensor but they changed it and drove for a week.. issue seems to be resolved

 

[mattkh]

..... turns out the air flow sensor was bad.

Are there two air flow sensors on your car?

 

[Steve@Avantgarde]

It won't give an air leak fault if there is no air leak.

The EGR cannot be jammed as its electric and it goes through an open/close procedure when the engine is started. If it jams it will have a specific fault code for it. The EGR code is there because the ECU has shut down the EGR system as it has a correlation error and it doesnt want to cause an overboost. Its a consequential fault, not an actual problem to fix.

The algorithm fault usually appears because the boost pressure that the turbo creates is measured but the manifold air pressure sensor reads a loss, there is a too large a correlation error and that code is effectively telling you that there is a loss of pressure between the two. So the obvious thing is to look for an air leak And that is usually because the inlet manifold has a snapped bolt causing an air leak.

You need to smoke test the inlet system and use a borescope to see what is going on under the manifold. Cylinder 2 is usually the culprit.

I have replaced loads of them for that specific fault code. The guided fault finding on STAR will tell you to measure the boost pressure and if it reads a loss on the machine, to inspect the charge air system for leaks.

 

[Muddy1987]

It won't give an air leak fault if there is no air leak.

The EGR cannot be jammed as its electric and it goes through an open/close procedure when the engine is started. If it jams it will have a specific fault code for it. The EGR code is there because the ECU has shut down the EGR system as it has a correlation error and it doesnt want to cause an overboost. Its a consequential fault, not an actual problem to fix.

The algorithm fault usually appears because the boost pressure that the turbo creates is measured but the manifold air pressure sensor reads a loss, there is a too large a correlation error and that code is effectively telling you that there is a loss of pressure between the two. So the obvious thing is to look for an air leak And that is usually because the inlet manifold has a snapped bolt causing an air leak.

You need to smoke test the inlet system and use a borescope to see what is going on under the manifold. Cylinder 2 is usually the culprit.

I have replaced loads of them for that specific fault code. The guided fault finding on STAR will tell you to measure the boost pressure and if it reads a loss on the machine, to inspect the charge air system for leaks.

hi I’ve got an issue with my sprinter it’s coming up as a air intake leak but seems to be no leaks. Some advice if anyone can help. I’ve had my sprinter put on the star diagnostics which the mechanic has said the egr valve on the live data is sticking but another mechanic is questioning if it was the EGR it would show a fault code. Currently showing up as a leak detected in air take system. Thanks

 

[mattkh]

hi I’ve got an issue with my sprinter Thanks

Hi
A bit more info about your sprinter will help. Year? Mileage?

 

[LostKiwi]

hi I’ve got an issue with my sprinter it’s coming up as a air intake leak but seems to be no leaks. Some advice if anyone can help. I’ve had my sprinter put on the star diagnostics which the mechanic has said the egr valve on the live data is sticking but another mechanic is questioning if it was the EGR it would show a fault code. Currently showing up as a leak detected in air take system. Thanks

If there's a code there's almost certainly a leak. You just need to look harder.
Common places are as Steve mentioned, intercooler or split boost hoses. These can be hard to see.

 

[Steve@Avantgarde]

Inlet manifold bolts snapping are very common too, more so on the commercial stuff.

 

[Uncle Benz]

Inlet manifold bolts snapping are very common too, more so on the commercial stuff.

luckily the commercial version of the manifold has no swirl flaps and is a fraction of the price

 

[Muddy1987]

Sorry it’s a 2014 plate with 130,000 miles. It’s a 513 euro6. Changed EGR and pressure valve but no luck cost of £400 in parts


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