Smart Fortwo's Transmission Nightmare: Warning Signs & Fixes

I dealt with very similar symptoms on my 2017 Smart Forfour Diesel at 155000km. The transmission issues and warning lights pointed to a failing oil cooler and damaged pressure sensor connection. The grinding noise and emergency mode activation were caused by inadequate cooling system performance. The oil cooler had developed a coolant leak, which reduced transmission fluid cooling efficiency. The pressure sensor connection had corroded, sending incorrect readings to the transmission control unit. The repair required: Complete leak detection of the cooling system, Replacement of the transmission oil cooler, New pressure sensor with wiring harness, Transmission fluid flush and refill This was a serious issue that required immediate attention to prevent permanent transmission damage. After the repair, the transmission shifted smoothly again, all warning lights cleared, and the emergency mode deactivated. From the symptoms described, there seems to be a strong similarity to the cooling system and sensor issues I experienced. Having a specialist perform proper diagnostics would be advisable, as general mechanics sometimes misdiagnose these specific transmission cooling problems.

Thanks for sharing your experience with the oil cooler and transmission issues. Your symptoms match mine exactly. After reading your reply, I took my Smart to a transmission specialist who confirmed similar problems with the cooling system. Did you notice any other car overheating issues after the repair was completed? My radiator coolant levels seem fine now, but I want to keep an eye on potential recurring problems. The shop also recommended installing a pressure gauge to monitor the system. By the way, can you recall the total repair cost for your oil cooler replacement and transmission work? It would help me compare if the quote I received is reasonable.

Since having the radiator coolant pressure sensor fixed, my Smart has been running perfectly with no overheating issues. The repair was straightforward, just needed a new cable connection which cost 95€. The pressure sensor itself was actually fine once properly connected. Installing a pressure gauge is a smart preventive measure. Regular monitoring can help catch any future cooling system problems early. The transmission specialist did a great job identifying the root cause, which turned out to be much simpler than a full oil cooler replacement in my case. The leak detection test showed no other cooling system issues. The radiator coolant levels have stayed consistent since the repair. Make sure to have the coolant levels checked during regular maintenance to prevent any transmission cooling problems from developing again. My repair costs were much lower than initially expected since only the sensor connection needed fixing rather than replacing the entire oil cooler. If your quote is significantly higher, it may include additional necessary repairs that weren't needed in my case.

After following the advice in the forum, I took my Smart to a transmission specialist last week. They diagnosed a faulty oil cooler and damaged pressure sensor, matching exactly what was described. The cooling system inspection revealed significant coolant leakage affecting the transmission. The total repair came to 850€ including: New transmission oil cooler, Pressure sensor replacement, System flush and refill, Labor costs The cooling fan is now working properly and all warning lights have cleared. The transmission shifts smoothly with no more grinding noises or emergency mode issues. Regular monitoring shows stable radiator coolant levels and normal operating temperatures. The mechanic also installed a pressure gauge for preventive monitoring, which gives me peace of mind. The repair cost was worth it to avoid potential transmission failure. Overall, very glad I sought a second opinion from a specialist rather than continuing with the initial incorrect diagnosis.