Any kind of smoke coming out of the exhaust pipe means that your car is under some sort of stress. Your tailpipe will send out smoke in different colors depending on what the problem is. This will give you a good idea about the kind of service or repair your car might need as your classic car is giving you the meaning of a car’s smokey exhaust.
Most of the time, your car’s exhaust should barely even be noticeable, quietly pumping out spent gasses from the combustion process at the back end of your vehicle. But if a problem were to arise, then blue, white, gray, or black smoke could start to appear from the exhaust pipe.
This unusual exhaust smoke could be coming out of your exhaust when the car is stationary or accelerating, and it may well cause an immediate sense of dread that an expensive repair bill is on the horizon. While exhaust smoke from petrol or diesel cars could indeed be a sign of a serious mechanical issue, however, this is not always the case.
So, what exactly does a smoking exhaust mean? There are several potential causes of a smokey exhaust from your car’s rear end, and our guide is here to help you figure out what is going on with your car.
Diagnosing A Smokey Exhaust
The first step is to identify exactly when the smoke is coming out of your car’s exhaust. If it only appears when you are accelerating, that might indicate a different problem than if it only appears when stationary or is a constant when the engine is running.
Once you’ve worked out when the smoke occurs, next you need to try and determine what kind of smoke it is. Is it white, grey, or with a hint of a blue tinge to it? Or is it thick and black? Does it evaporate as soon as it is in the air? Or does the smoke linger and come with an acrid smell? If it is black smoke, then does it leave soot on the road under the exhaust tip when the car is stationary?
The main causes of smoke from an exhaust can vary depending on your car and its condition. If your car is well maintained and serviced regularly, then any visible emissions from your exhaust are unlikely to be anything of concern, but it is well worth checking anyway.
The real issue is with cars that have been poorly maintained, as smoke from the exhaust could be a clear sign of neglect. The smoke you see can be caused by different things, depending on whether your car has a petrol or diesel engine.
We have separated the different kinds of smoke you will come across to help you quickly identify what problem causes which smoke.
White Smoke
White smoke coming from the exhaust, with a faintly sweet smell to it, will usually mean the engine is burning coolant. This can happen a couple of different ways, such as:
- Bad head gasket
- Cracked cylinder head
- Cracked engine block
Fortunately, the last two are relatively rare occurrences. For a cylinder head or engine block to crack, there usually must be serious trauma to the engine beforehand in the form of extreme heat. This will normally be the result of an engine being run without coolant or oil in it. Perhaps because of a bad leak. Then it overheats to the point of cracking.
Head gaskets can get a bad rep, but it is not always a death sentence for your engine. With enough miles on your car the head gaskets are bound to be compromised at some point. For many cars, it is an expensive, but worthwhile, repair.
Black Smoke
If you see black smoke coming from the exhaust, it is a sure sign the engine is burning too much fuel. In this case, it will probably smell like gas. This is rare to see at idle, but very common under heavy load.
If your car has this problem, make sure to get your engine a tune-up. Causes could include leaky injectors, a bad fuel regulator, faulty sensors, or even carburetor issues.
By far the most common form of exhaust smoke is going to have a blue tint to it, and this means the engine is burning oil. There was a time many years ago when people just accepted some amount of oil consumption from their classic cars, but those days are mostly gone for newer cars.
Some of the possible causes of an engine burning oil include:
- Worn piston rings
- Worn valve seals
- Bad PCV system
- Heavy cylinder wear
- Bad head gasket
Some of these problems, like valve seals and piston rings, can simply be the result of an engine with very high mileage exhibiting the effects of high wear. If there is a small amount of oil being burned between oil changes, then perhaps it is not something you have to worry so much about.
Either piston rings or valve seals could require a rebuild of the cylinder head, and maybe the whole engine.
Gray Smoke
Gray smoke can be ambiguous sometimes. There is a turbocharger in your cars. Its task is to increase your car’s engine efficiency by pulling more air from the gas chambers and allowing it to drive the turbine to burn fuel efficiently. However, sometimes a bad or failing turbo charger can result in incomplete combustion. Gray smoke and blue smoke usually have similar causes, that is, burning oil.
Gray smoke can also be forming because of auto transmission fluid. Auto transmission fluid is used to keep the car’s internal components lubricated. Its main function is to keep the car’s cooling system running properly, to prevent the metallic components from wearing out and keep the gaskets in proper working condition. But, if you have a broken transmission modulator, it can make the transmission fluid leak into the combustion chambers and get burned up.
Moreover, another cause of gray smoke can be a jammed PCV valve. The PCV system (Positive Crankcase Ventilation) also reduces toxic emissions and sends them back to where combustion takes place. However, if there is a broken or jammed PCV valve, it can make the air and gas get stuck inside the ventilation system and result in pressure build up, which in turn leads to leakages.
No Smokey Exhaust?
Should your car ever have smoke come from the exhaust? Well, a small amount of white, vapor-like smoke at startup is nothing to worry about. Condensation will leave some water residue in the exhaust system, and this water will have to get burned when you start the car. Once the engine comes up to temperature, the vapor should stop, and nothing will be visible from the exhaust.
Finally
You do not have to be an expert mechanic to see the signs of trouble with your classic car. Knowing the different types of smokey exhaust that may come from the rear of your classic car, and addressing problems before they get worse, could mean the difference between a simple repair and a complete engine rebuild.
