Q: My car is smoking - 2008 Mercury Milan

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I've been having some issues with my car and the coolant resevoir, I believe. So when I'm driving my car is fine, but if I'm sitting in traffic for too long with my car running, after a while my car will start to smoke white smoke. I look and see that the coolant is gone. I have used water in the mean time but from calculating my drive from home to work which is about 45 minutes today, after filling the resevoir before leaving home, once I got to work it was half full. I'm so confused as to what the problem is. Of course once my car starts to smoke the themostat shows "H". Please help with some information I can use to find out something to do. I'm not sure if its a leak or what. I did come across the product Blue Devil Radiator & Block Sealer. I'm not sure if that would be for my situation or not but if able to give info on it I really would appreciate it.

My car has 81000 miles.
My car has an automatic transmission.

You definitely have a coolant leak. Where it is leaking from is important in that it could be the radiator cap releasing pressure as it is designed. A vehicle that displays the symptoms you have described in traffic indicates that the cooling fan is not working. The cooling fan is there to push or pull air through the radiator when the car is not moving. When the car is moving, air is moving through the radiator and it is not necessary for the cooling fan to operate. Once you are moving slow enough, however, the cooling fan kicks in to move air through the radiator.

If the cooling fan does not turn on while you are sitting in traffic, your car will steadily climb in temperature. As the temperature rises, the pressure in the cooling system rises. I suspect the cooling system leak is the radiator cap releasing this excess pressure so something else in the cooling system won’t burst. This is one of several things the radiator cap is designed to do. So you have a leak, but it is most likely the cooling system protecting itself.

I recommend you don’t drive your car in traffic until the cooling system operation has been looked into. Either way, if you are seeing white smoke, or what is most likely steam coming from under the hood, then this can damage your car further and become a much larger repair. You should have this looked at immediately.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the car is overheating and suggest any needed repairs.

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