Easy folks – we haven’t been endorsed by the Surgeon General to give a lecture on the negatives of smoking and it’s relation to your health. We’ll leave that expert advise to your doctor. We will however, pass along some useful tidbits on smoke and how it relates to your vehicles health.
First off, we’re going to “clear the air” about a few things. We will be limiting our discussion to smoke that comes out the tailpipe(s). In our humble opinion, if there is smoke coming from any other location – be it under the hood or from inside the of the vehicle – you need to have that checked out ASAP!
Now, like it or not, at some point your vehicle will start smoking; and it’s not because it’s starting to hang around with other delinquent makes and/or models. Even when the vehicle is brand new, especially when the temperatures dip below freezing, your vehicle will emit visible exhaust smoke. It should be a whispery looking white-ish smoke that disappears quickly into the atmosphere. This is perfectly natural, as trace amounts of water are part of the combustion cycle and exit out the exhaust. What you do need to look for, especially when the vehicle gets older and has quite a few miles on the odometer are the following:
Black Smoke - this color smoke is the least troublesome. If you own an older diesel engine truck, this is actually normal at start up – but you should not experience this with a vehicle that has a gasoline engine. If you do, chances are the air to fuel mixture (or ratio) is too rich, which means there is too much gas being dispensed and thusly being burned. Possible causes could be a fuel injector that is starting to malfunction where it is leaking or releasing too much fuel pressure. It may also be as simple as a dirty air filter or worn spark plugs that are in need of a change.
Blue Smoke - This color seems to be the most common or the smoke most people are familiar with. It is most common on vehicles that have well over 100,000 miles on the clock. It almost always means one thing – the engine is burning oil. More specifically, the main cause is that oil is seeping past the piston rings in the engine (or the pistons themselves are worn and/or damaged), or the valve guides and/or valve guide seals in the cylinder head(s) are worn out. This type of smoke also smells like burnt toast (don’t ask how we know this). What you should check is the oil dipstick. If the oil level is low, add the appropriate amount. Do not let the oil level get so low because then more engine damage may occur. You should make an appointment with your trusty mechanic so they can perform a compression check (or what’s also known as a leak down test) to further diagnose the problem.
White Smoke - This can be the most feared colored smoke of all. It usually means that either coolant or transmission fluid is being burned in the exhaust. If the smoke involves coolant, the engine either has a leaking cylinder head gasket or the cylinder head itself is cracked. If the cause is transmission fluid, that most likely means the engine is sucking fluid through a vacuum hose from the transmission.
The exhaust fumes may have a slightly sweet smell if coolant, or a burned smell if transmission fluid. The smell is usually pretty strong, so it’s not like you have to stick your nose anywhere near the tailpipe – so please make it a point not to do so! If you can, check the coolant level and the transmission fluid level. If the coolant is low and/or the engine has been overheating, have your mechanic pressure test the cooling system to see if it holds pressure. If it does not, the head gasket is probably leaking and needs to be replaced. If only the transmission fluid level is low, add the required type of transmission fluid to bring it back up to the full mark. Then inspect the vacuum hose from the transmission to see if there’s any fluid inside. If it is passing fluid, replace the vacuum modulator valve on the transmission.