Smart Fortwo Coolant Level Check & Leak Detection Guide

I had a similar issue with my 2016 Smart Forfour last winter. With some basic car maintenance experience, I initially tried troubleshooting it myself. First, check your coolant level when the engine is cold to avoid any risks. The radiator cap should only be removed when the engine has completely cooled down. Look for any visible leaks around the water pump, radiator hoses, and the bottom of the radiator itself. In my case, there was an issue with faulty wiring to the coolant level sensor. The workshop found that the cable connection was damaged, causing incorrect readings and triggering the check engine light. The repair took about 2 hours and cost 95€. To properly diagnose your situation, could you share: Any visible coolant leaks or puddles under the car? Are you noticing any engine overheating? Does the temperature gauge show normal readings? Have you recently had any other cooling system work done? Its important to address coolant issues promptly to prevent potential head gasket problems or serious engine damage. While sensor issues are common, its best to have a professional check the entire cooling system to rule out more serious problems.

Thanks for the thorough response. My Smart has 113142 KM on the clock, and checking under the car this morning, I noticed a small puddle near the front passenger side. The temperature gauge reads normal, but the coolant reservoir level seems lower than usual when cold. The cooling fan appears to run more frequently than before, especially in slow traffic. I checked all visible radiator hoses and found no obvious cracks, but there is some dampness around the lower hose connection. Maybe air pockets have formed in the system since the level dropped. I will have it checked professionally rather than risk any engine damage. Do you think 2-3 hours labor time is reasonable for a thorough inspection and potential hose replacement?

Thanks for the update. Based on your description, that damp area and puddle near the lower hose connection is concerning. On my Smart, a similar leak turned out to be a loose hose clamp, but the coolant leak had already allowed air pockets to form in the system. 2-3 hours labor is reasonable for a proper diagnosis and repair. The shop will need to: Pressure test the cooling system, Check the radiator cap seal, Inspect the water pump for leakage, Verify proper coolant circulation, Bleed any trapped air from the system The increased cooling fan activity combined with a dropping coolant level strongly suggests a leak that needs addressing. My repair included replacing both the hose and clamps, plus a system flush to remove air pockets, taking about 2.5 hours total at 185€ including parts. Just make sure they check the head gasket condition while diagnosing, since prolonged low coolant can sometimes lead to more serious issues. Better to catch any problems early.

That frequent fan operation combined with the coolant leak really points to something that needs fixing soon. The dampness around that lower hose connection matches what happened with my vehicle. I will schedule it in for service this week. I appreciate knowing the typical repair times and costs. The 2.5 hours sounds reasonable for checking everything properly. My main concern was air pockets forming in the system since the coolant reservoir level dropped, but a professional inspection should sort that out. Think I will ask them to do a complete cooling system check while they have it, including the water pump and head gasket condition. Rather spend a bit more now on proper diagnostics than risk bigger problems later. Will update once I know what they find. Thanks for sharing your experience, it helped confirm I am taking the right approach with this.