Mercedes C Klasse Hybrid Coolant Loss

Oh man that sounds familiar I had a similar coolant problem with my old Nissan a while back The coolant kept disappearing but no visible leaks anywhere It drove me nuts Could it be the radiator cap not sealing properly I'm no expert but is there coolant on the cap I hope it's not the head gasket That would be a bummer

Thanks for the quick reply I'll double check the radiator cap for any residue When you had this issue with your Nissan did the disappearing coolant also trigger a check engine light And do you remember what ended up being the cause in your case

Yeah the check engine light was on constantly I honestly can't remember the exact code but it was definitely related to the coolant system After checking the water pump the hoses and even sniffing around for a coolant leak I took it to a workshop because I did not wanted to risk engine overheating They found a tiny crack in the radiator itself that was only leaking when the engine was hot and under pressure Hopefully it is something simple for you too

Thanks again for sharing your experience It helped me to narrow things down I took it to the shop and you were right it was a small coolant leak The cable/plug connection to the coolant sensor was indeed defective They replaced the connection and the sensor pressure tested the system and all is well now The total repair cost was 95€ Appreciate the advice