Smart Fortwo Engine Overheats Despite Slow Warm-up

Had the exact same symptoms with my 2004 Smart Forfour gasoline model. Based on some experience working on cooling systems, this sounds very familiar. The temperature fluctuations you describe point strongly to a faulty map thermostat. When mine failed, it showed identical behavior, slow warmup combined with overheating during regular driving. The thermostat housing was tested and revealed the map thermostat was sticking, preventing proper coolant flow regulation. Had it fixed at my regular workshop, total repair came to 350€ including parts and labor. The mechanic replaced the entire thermostat housing assembly and flushed the coolant system while at it. Since then, the cooling fan cycles normally and temperature stays steady. To provide more specific guidance: What temperature readings are you seeing? Is the cooling fan running constantly or intermittently? Also, when was the last coolant system service done? These details would help confirm if your issue matches what I experienced. Quick tip: While waiting for repairs, keep monitoring the temperature sensor readings closely and avoid extended highway driving until fixed. A failing thermostat can lead to engine damage if left unchecked.

Had the exact same symptoms with my 2004 Smart Forfour gasoline model. Based on some experience working on cooling systems, this sounds very familiar. The temperature fluctuations you describe point strongly to a faulty map thermostat. When mine failed, it showed identical behavior, slow warmup combined with overheating during regular driving. The thermostat housing was tested and revealed the map thermostat was sticking, preventing proper coolant flow regulation. Had it fixed at my regular workshop, total repair came to 350€ including parts and labor. The mechanic replaced the entire thermostat housing assembly and flushed the coolant system while at it. Since then, the cooling fan cycles normally and temperature stays steady. To provide more specific guidance: What temperature readings are you seeing? Is the cooling fan running constantly or intermittently? Also, when was the last coolant system service done? These details would help confirm if your issue matches what I experienced. Quick tip: While waiting for repairs, keep monitoring the temperature sensor readings closely and avoid extended highway driving until fixed. A failing thermostat can lead to engine damage if left unchecked.

Thanks for the feedback on my Smart cooling system issue. Latest service was at 88376 KM. The temperature sensor shows readings jumping between 70-115C during normal driving. The cooling fan seems to run almost constantly once warm, which seems excessive. Getting a proper diagnosis has been tricky since the temperature control behavior is so erratic. The thermostat housing feels very hot to touch after driving, while other parts of the cooling system remain cooler, suggesting restricted coolant flow. Based on your experience, the symptoms do match a failing thermostat. Will get the system pressure tested to confirm before proceeding with repairs. Good tip about avoiding highway driving. Have been keeping trips short and monitoring engine temperature closely until this gets resolved.

Thanks for the feedback on my Smart cooling system issue. Latest service was at 88376 KM. The temperature sensor shows readings jumping between 70-115C during normal driving. The cooling fan seems to run almost constantly once warm, which seems excessive. Getting a proper diagnosis has been tricky since the temperature control behavior is so erratic. The thermostat housing feels very hot to touch after driving, while other parts of the cooling system remain cooler, suggesting restricted coolant flow. Based on your experience, the symptoms do match a failing thermostat. Will get the system pressure tested to confirm before proceeding with repairs. Good tip about avoiding highway driving. Have been keeping trips short and monitoring engine temperature closely until this gets resolved.

Looking at your temperature readings of 70-115C and constant cooling fan operation, this exactly mirrors what my Smart was doing before the repair. Those irregular temperature swings combined with the cooling fan running continuously are classic signs of a failing thermostat. The hot thermostat housing you mentioned while other areas stay cooler is another red flag I noticed on mine. This temperature differential occurs when the thermostat sticks partially closed, creating a coolant flow restriction and leading to engine overheating in specific areas. After my repair, the temperature stabilized around 90C and the cooling fan returned to normal cycling. The pressure test you mentioned is smart, this helped identify the issue on mine and ruled out any coolant leaks in the system. Quick observation on your service interval, at 88376 KM, your Smart is right around when these thermostat failures commonly occur. Mine failed at similar mileage. The full thermostat replacement resolved both the slow warmup and overheating issues completely. Keep an eye on your temperature sensor readings until the repair. If you notice the temperature climbing above 115C, best to stop and let things cool down to prevent potential engine damage.

Looking at your temperature readings of 70-115C and constant cooling fan operation, this exactly mirrors what my Smart was doing before the repair. Those irregular temperature swings combined with the cooling fan running continuously are classic signs of a failing thermostat. The hot thermostat housing you mentioned while other areas stay cooler is another red flag I noticed on mine. This temperature differential occurs when the thermostat sticks partially closed, creating a coolant flow restriction and leading to engine overheating in specific areas. After my repair, the temperature stabilized around 90C and the cooling fan returned to normal cycling. The pressure test you mentioned is smart, this helped identify the issue on mine and ruled out any coolant leaks in the system. Quick observation on your service interval, at 88376 KM, your Smart is right around when these thermostat failures commonly occur. Mine failed at similar mileage. The full thermostat replacement resolved both the slow warmup and overheating issues completely. Keep an eye on your temperature sensor readings until the repair. If you notice the temperature climbing above 115C, best to stop and let things cool down to prevent potential engine damage.

Thanks everyone for the detailed feedback on my Smart cooling system concerns. Based on all the information shared, I am now confident the thermostat is the core issue. The matching symptoms, especially the temperature swings between 70-115C and constant fan operation, really helped confirm this. Going to book it in next week for the thermostat housing replacement and coolant system flush. The 350€ repair cost seems reasonable considering the work involved. Will make sure they pressure test the system first to verify no other issues are present. Meanwhile, following the advice about limiting driving and keeping a close watch on the temperature sensor readings. Really appreciate all the specific guidance provided, helped avoid potentially expensive engine damage from running too hot. Will report back on the repair results once completed. The detailed experiences shared here made it much easier to diagnose the problem and understand the repair process.

Thanks everyone for the detailed feedback on my Smart cooling system concerns. Based on all the information shared, I am now confident the thermostat is the core issue. The matching symptoms, especially the temperature swings between 70-115C and constant fan operation, really helped confirm this. Going to book it in next week for the thermostat housing replacement and coolant system flush. The 350€ repair cost seems reasonable considering the work involved. Will make sure they pressure test the system first to verify no other issues are present. Meanwhile, following the advice about limiting driving and keeping a close watch on the temperature sensor readings. Really appreciate all the specific guidance provided, helped avoid potentially expensive engine damage from running too hot. Will report back on the repair results once completed. The detailed experiences shared here made it much easier to diagnose the problem and understand the repair process.