Smart ForTwo Brake Pedal Issues: Fluid Leak Warning Signs

I had a pretty similar issue with my Smart Forfour from 2019. Having some experience working on basic car maintenance, I first thought it was just low brake fluid, but it turned out to be more serious. The spongy brake pedal combined with low fluid levels often indicates a leak in the hydraulic brakes system. The master cylinder was failing, allowing brake fluid to slowly leak out. This explained the inconsistent pedal feel and dropping fluid levels. The repair involved: Complete brake fluid replacement, New master cylinder installation, Bleeding the brake lines, Full system pressure test Total cost came to 480€ for parts and labor. Not cheap, but essential for safety. The car brakes now feel solid and responsive again. What mileage is on your Fortwo? Have you noticed any fluid spots under the car when parked? Knowing these details would help determine if you might be facing the same issue. Also, even though the warning light hasnt activated, its important to get this checked soon since brake problems can escalate quickly. Before taking it to a shop, check around your master cylinder and brake lines for any visible wetness or brake fluid residue. This can help pinpoint where the leak might be.

Thanks for the detailed insight. My Fortwo has 77764 KM and had its last service 3 months ago. After reading your experience, I checked around the master cylinder and brake lines this morning, found some dampness near where the brake lines connect to the master cylinder. The symptoms match exactly what you described with the spongy brake pedal. Seems like I might be looking at a similar repair cost. Better to fix it now than risk any brake failure. Will book it in with a shop tomorrow. Been checking the brake fluid level daily now and its definitely dropping faster than normal. No visible puddles under the car yet, but that dampness around the master cylinder connection is pretty telling.

Yep, that dampness around the master cylinder connection is exactly how mine started too. Smart move checking it daily, I learned the hard way that brake fluid doesnt just evaporate on its own. The symptoms are identical to what I experienced, right down to the gradual fluid loss without obvious puddles. The brake system in these cars is generally reliable, but the master cylinder seals can wear out around this mileage. Quick tip from my repair experience: Ask the shop to check the brake lines while they are replacing the master cylinder. My mechanic found that the constant pressure changes from the leaking cylinder had started to stress one of the nearby brake lines. Getting both fixed at once saved me from potential future issues. The repair should take about 4-5 hours if its just the master cylinder. Make sure they do a thorough brake system pressure test afterward. My car has been perfect for 25000 KM since the fix, with no more fluid loss or spongy pedal feel. The 480€ I mentioned included a full brake fluid flush, which you should definitely get done while they are working on it. The old fluid can contain moisture and debris that might affect the new components.

You are right, my car has shown identical symptoms to yours. Just booked it in for tomorrow morning at the shop, they quoted roughly 500€ for a full brake system inspection, master cylinder replacement, and brake fluid flush. The daily checks show the fluid level keeps dropping slowly. That dampness near the master cylinder connection has me convinced its the same issue you faced. Better to fix it now than risk any safety issues down the road. Good tip about checking the brake lines while they are in there. When I called the shop, I mentioned your experience and asked them to inspect the lines for any stress damage. They agreed it makes sense to check the whole hydraulic brakes system while doing the work. Really helpful to hear your car has been running well since the repair. Makes me feel better about spending the money to get it fixed properly rather than just topping up the fluid and hoping for the best. Will update once the work is done, but seems like I caught it early enough before any serious brake failure could occur.