alexandermond15
C30 Hissing Sound and Fuel Consumption
Summary of the thread
A 2007 Volvo C30 owner reported higher fuel consumption, a check engine light, and a loud hissing sound during acceleration, suspecting an intake leak, possibly from a vacuum hose. Another participant suggested checking the intake hose between the air filter and the intake manifold, as a similar issue was experienced with a different car. Upon inspection, the problem was confirmed to be a cracked intake hose, which was replaced, resolving the fuel consumption issue, eliminating the hissing sound, and turning off the check engine light.
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4 comment(s)
alexandermond15 (community.author)
Good point about the intake hose. I haven't checked that specifically yet. I'll give it a look. The hissing definitely gets louder as I accelerate, so it changes with engine load. If it's a leak there, is it usually obvious, or could it be a small crack that's hard to spot?
noahschwarz9
On my Astra, it was a split right on the underside of the hose, where I couldn't easily see it. Because the hissing gets louder with acceleration, that really points to a leak that gets worse under pressure. Honestly, it's probably worth taking it to a workshop; they will have the right tools to properly diagnose the problem.
alexandermond15 (community.author)
The advice was spot on! It turned out to be a cracked intake hose, just like you suspected. The shop replaced it, and it cost me around 100€. Fuel consumption is back to normal, no more hissing, and the check engine light is off. Appreciate the help!
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VOLVO
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C30
noahschwarz9
Sounds familiar! I had almost the exact same symptoms on my old Opel Astra, but with a slightly different engine. Higher fuel consumption and the hissing sound were the first things I noticed. Did you check the intake hose between the air filter and the intake manifold? It might be cracked. Is the hissing constant or does it change with engine load?