My kenmore window unit AC started blowing a white smoke like substance. It seems to be cooling fine. What is this and is it a concern?

There should not be any smoke, if any smoke, would be outside where the motors live in the AC window unit. What you see is either oil, or condensed humidity. Neither may smell, odorless. If it's oil, there won't be any more cooling and can smear when touched.
There may be more to your AC if it has electric heat, humidifier, dehumidifier, etc.etc.

If you have overheated your car recently, then you possibly have a blown head gasket. Take off your oil fill cap (with engine off) and inspect to see if there is a milky substance underneath the cap. If so, bad news- head gasket. You can also check the oil dipstick for the same substance to verify bad head gasket, but usually it has to be pretty bad (gasket) or driven for a while before exhibiting any signs. The oil fill cap is a pretty good indicator. With the car cool, you can open the radiator cap and look and smell for anything other than coolant (fuel smell or oil slick). If so, probable head gasket.

White means coolant in the cylinder. With high mileage, the head can crack without over heating. Check the oil filler cap for a milky brown substance to prove there's coolant and oil mixing.

yes your not seeing things im ase certified in auto ac,ford,chevy honda, also. what is happening is fine dust from the ac evaporator ,inside the air tubes and sometimes fog and moisture all can come out you only need to worry if the system starts blowing out ice crystals or it gets worse then it will need to be looked at.

Shirley, it's just a harmful mist. This usually occurs on hot, high humidity days. Keeping the air intake filter clean, will help to reduce it.

I hope this helped you and thanks for choosing FixYa.

dont really think its smoke just water vapor, the difference in temp causes this. iassuming it doesnt do this all the time may be alittle dirty when you can pull the unit out take it to the car wash and give it a bath dont spray the controls and let it dry good before starting it back up make sure your filter is clean and remember ac units remove heat they dont add cool i know this sounds confuseing but thats how they work and dont worry about the vapor its normal when you fire it up.

it could be your choke stuck, but check you oil level and smell it does it smell like fuel. if so have your carb check out. Little lube on the chock lever. you may want to have your compression check and a leak down test done.

You should replace the cooling fan. With the ac on and no cooling fan, high pressure builds in the condensor and compressor bogging the engine down. When it gets too high a relief valve dumps and you get what appears to be white smoke. It's actually freon, hence the smell. I've replaced several PT cooling fans with the same symptoms.

It is probably the compressor. You will need to check if the compressor is being called to come on. Do you hear the compressor running? If you do, I would remove the unit from the wall or window, and wash it down real good with a hose being careful not to get the electronics wet. If not and the unit sound different than it did before, it's probably time to buy a new one.

There are a lot of variables with A/C concerns. Without being able to answer these, the smoke you saw was originating from the clutch? If so, can you see any kind of oil seeping from the seal behind it? You might also look for oil stains on the hood blanket above the compressor. If there is oil present, you may have a seal leaking causing premature clutch failure. Since you were in traffic at a stop, you might want to check the condensor and the radiator for any kind of obstruction. Also that the fan is coming on when the pressure starts to rise. If you have an oil leak it might be a good time to replace the compressor. If not, it could be just an early clutch and bearing failure. Also, don't forget to check the belt for overheat damage.