Smart Fortwo Diesel Hissing Points to Critical Air Leak

Having dealt with a similar issue on my Smart Forfour diesel (2003), I can share some relevant experience about intake manifold problems. After noticing the same symptoms, increased fuel consumption and that distinctive hissing noise, I discovered it was indeed an intake hose leak. The workshop performed leak detection tests using smoke testing equipment to pinpoint the exact location. The problem turned out to be a cracked intake hose near the turbocharger connection. These hoses tend to deteriorate over time due to heat exposure and regular engine vibration. The repair involved replacing the faulty intake hose and performing a thorough check of all connecting points. Total cost was 100€, including parts and labor. After the fix, the engine misfire symptoms disappeared completely, and fuel consumption returned to normal. To better assist with your specific case, could you provide: Current mileage, Any recent maintenance history, Whether the check engine light shows any specific error codes, If you notice the hissing more during specific driving conditions These details would help determine if your issue matches what I experienced and could lead to a more accurate diagnosis. Remember that driving with an intake leak can cause long-term damage to your turbocharger and engine components, so getting it checked promptly is important.

After getting the vacuum hose and all connecting points thoroughly checked at my last service, I found the issue was related to a cracked throttle body gasket. The service technician discovered this after performing a smoke test. The check engine light disappeared once the gasket was replaced. My car has 151916 KM and shows much better fuel economy after the repair. The total fix, including parts and labor, came to 180€. The hissing noise is completely gone now, and engine performance has returned to normal. For anyone facing similar issues, having a proper diagnosis with specialized equipment made all the difference in identifying the exact problem location. The intake manifold and surrounding components should always be checked thoroughly when experiencing these symptoms.

Thanks for the update about the throttle body gasket repair. My Smart Forfour had actually developed cracks in the same area about 6 months after the initial vacuum hose replacement I mentioned. The symptoms were nearly identical, poor fuel economy and that unmistakable hissing sound. The throttle body gasket is definitely a common failure point on these engines, often overlooked during initial diagnosis. My repair costs were similar, around 170€, and the smoke test was crucial in finding the exact leak location. The engine misfire issues I experienced cleared up immediately after the fix. These intake system problems can be tricky to diagnose without proper equipment. The turbocharger puts additional stress on all the connecting components, making regular inspection of gaskets and seals important. A failed throttle body gasket can cause the air-fuel mixture to run lean, leading to both poor performance and potential engine damage if left unchecked. Good to hear your fuel consumption has returned to normal. These repairs tend to be very effective long-term solutions when done properly with quality parts.

Thanks for the detailed follow up about the throttle body repair. Based on my car's symptoms and the success of your repair, I decided to take mine in for a professional diagnosis. The leak detection test revealed exactly what you described, a faulty throttle body gasket. My mileage is now at 151916 KM and the repair cost came to 180€. The engine misfire symptoms have completely disappeared and the check engine light is finally off. Fuel economy has returned to normal levels, saving me money at each fill-up. The turbocharger is working properly now that the intake system is properly sealed. No more concerning hissing noises during acceleration. For anyone reading this with similar symptoms, I strongly recommend getting a proper smoke test done rather than guessing at the problem. The service technician mentioned these gaskets commonly fail at higher mileages, and regular inspection can help catch issues before they affect engine performance. Having the right diagnostic equipment made all the difference in pinpointing the exact location of the leak.