achimfrank2

Viano Diesel Engine Issues Resolved

My Mercedes Viano, build year 2015 with a diesel engine, is giving me headaches! The check engine light is on, and I've noticed a real drop in power, especially when accelerating. Plus, there's a lot of smoke and a loud hissing sound, and the engine runs rough. Fuel consumption has gone up too. It also feels like the car is jerking when accelerating, like something's holding it back. Mileage is 112017 km. I suspect it's the EGR valve. Could this be caused by a vacuum leak in the exhaust gas recirculation system?

4 comment(s)

I had similar symptoms with my Vito. Reduced power, smoke, and the check engine light. It does sound like the EGR valve. The hissing noise is concerning though, as a vacuum leak can definitely impact the EGR system's performance, particularly in diesel engines. Is the hissing constant, or only under acceleration? Have you tried inspecting the vacuum lines for any obvious cracks or disconnections?

The hissing is mainly when accelerating, like the engine is struggling. I haven't checked the vacuum lines myself, as I'm not really familiar with that. Is it something I can easily check, or should I take it to a mechanic?

Given that you are not familiar with the vacuum lines and the hissing is prominent under acceleration, it is probably best to consult a qualified mechanic. The issue might not be just the EGR valve but something more complex, such as a vacuum leak affecting the entire recirculation system. I ended up replacing the EGR valve because it was completely jammed and the mechanic said that it was a common problem with diesel engines. The vacuum leak can cause the EGR valve to fail prematurely or reduce the effectiveness of the valve, as it is not opening and closing properly. The cost of the repair was around 355€. I recommend you do the same, it is better to have it checked by someone with the correct tools.

Thanks for the advice! I took it to the workshop, and you were spot on – it was the EGR valve, just like you said. Replaced it, and all the problems are gone. The hissing was indeed a vacuum leak near the EGR, so they fixed that too. Appreciate the help!

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