As people have already mentioned, steam indicates coolant leaking into your cylinders either through a blown head gasket, cracked head, or cracked cylinder liner / liner o-ring (if your engine has liners). That would be quite serious and you would need to have it looked at. Smoke that only comes out at startup would indicate that your valve stem seals are leaking, allowing a small amount of oil to get into your cylinders while the truck's not running. It's not really a big problem, as long as you remember to check your engine oil level every now and again, which you should be doing anyway.
The reason most people tell you that it must be steam is because the textbooks will tell you that burning engine oil will come out as blue smoke. I've had a lot of cars with worn rings / valve stem seals, and I would definitely describe the smoke that's come out of them as white, I've only ever seen a very slight blue colour to it. Source: Mechanic 9 years
Hope you like this question!Have a good day foryou!-
When the engine is cold, it's water / steam
Burn hydrocarbon and you get CO2 and H2O. Because the exhaust system is cold the water condenses into visible steam as it cools . Once the exhaust system warm up, the water vapour remains as a gas, and is invisible. Unless it's REALLY cold.
White smoke = water. Dark smoke = oil. That is probably as much as I listened to in college.
H2O vapor burning off with a cold exhaust that is warming up . . .
Leaky gaskets/head gasket ... Does it happen everytime or no?
I have some white smoke that comes from my exhaust when I crank my truck up. It does it after its been sitting for alil while. Maybe afew hours? Anyone know why? It blows out a nice size cloud of it for about 3 or 4 seconds.
