Blue Smoke From Exhaust
Common Causes And How To Fix

Blue smoke coming out of exhaust can be a sign of severe problems with your vehicle. If you determine it early, these problems can be fixed. Let’s look at the main causes of blue smoke and how to fix it.

What Does Blue Smoke Mean?

Blue smoke indicates your car engine is burning oil. It can happen when the piston rings, the valve guide seals or other components of the engine get worn out or damaged, causing oil leaking. The oil will flow into the combustion chamber, and then it is being burnt together with the fuel, creating blue smoke. It also creates smell which is harmful to your health.

Several things are causing the blue smoke coming out of the exhaust.

What Makes Blue Smoke From Exhaust When Starting?

1. Bad Valve Seals (Not diesel cars).

If you are not driving a diesel car, and you see blue smoke coming out of the exhaust, then the cause could be bad valve seals.

Every vehicle has valves that open and close. These valves are designed to open mechanically by pressure from a Rocker Arm. They let air and gasoline come into the engine. After the combination of air and gasoline has been burnt, they also allow the exhaust gas out of the engine. Oil is used to cover the top of the valves where the rocker arm applies pressure. Only valve seals prevent this oil from flowing into the engine. If the valves get damaged, the oil will come into the engine, which causes a blue smoke.

How to fix:

It is very easy to replace the valve seals and can be done at home by someone who can work on engines easily. You just need to be careful not to drop the valve into the engine. If your engine has an overhead cam, it will require more work to remove it to reach to the valve stem. First of all, you need to remove the spring from the valve and rocker arm, then remove the old Valve Stem Seal and replace it with the new one.

2. Damaged Glow Plug (Diesel cars).

To start a diesel engine, glow plugs play an essential role to cause ignition of diesel fuel. Once the engine is warmed up, the use of the glow plug is not necessary as the heat of the engine makes ignition of diesel fuel.

If glow plugs get bad, it will create blue smoke at startup until it has warmed up.

How to fix:

If your car has a glow plug, especially for diesel cars, replace it with a new one.

What Makes Blue Smoke From Exhaust When Accelerating?

1. Stuck PVC Valve

The first thing you should check if you noticed blue smoke is the PCV (Positive Crankcase Ventilation) Valve. The PCV Valve releases the pressure which builds up in the oil pan into the intake manifold where the engine gets its air for running. The intake manifold is connected with the air filter of the engine as well. If the PCV valve gets stuck, it will keep mixing the oil with air and other gases inside the engine. The combustion of this mixture will cause blue smoke.

How to fix:

PCV Valve repair is very simple and cheap. First of all, locate a tube which links to the intake manifold. Then keep following the tube back until you see the PCV Valve. Remove the old PCV valve and replace it with a new one.

2. Worn Engine

Each engine has pistons which are moving up and down a cylinder, and each of them has metal rings around its side. They are designed to help the piston forming a tight seal against the cylinder. So if the rings or cylinder is damaged, oil from below the piston will come up. Then the oil gets mixed with the air and gasoline and gets burnt, causing the blue smoke.

How to fix:

Clean The Engine. Irregular maintenance of your car can lead to the collection of debris in the engine. A clogged cylinder head can cause blue smoke. To clean it, remove the valve cover, and do the necessary cleaning. Also, clean the drain back holes carefully and recheck and reassemble them. After all of this, wait for 2 or 4 more days for the remaining oils to clean away.

3. Blown Turbo

Another reason for blue smoke can be a blown turbo if your car has a turbo. It is because either the turbo is damaged or a broken oil seal in the turbo. In both cases, they let oil into the intake of the engine.

How to fix:

It is not recommended to drive a vehicle with a blown turbo as bits of metal will be created due to the lack of oil in the turbo. And these bits of metal can come into the engine and damage the engine.
Before starting, try to determine what damage the blown turbo did. If the blown turbo did not break into small pieces, then you just need to rebuild it or replace it. If the blown turbo cut into small pieces, you might need help from a mechanic as your engine is damaged.

4. Transmission Fluid Loss

A modulator is designed to control the transmission shift in older vehicles with vacuum controlled automatic transmissions. If the modulator fails, it enables the engine to suck in transmission fluid. Then this transmission fluid burns, creating the blue smoke coming out of the exhaust.

How to fix:

Locate the transmission modulator, then remove it and replace with a new one. You also need to replace the vacuum line if damaged by transmission fluid.

As soon as you notice a blue smoke, determine the cause and fix it immediately.

Very often, you can notice blue smoke during the morning when you start the engine for the first time. If you don’t follow proper maintenance procedure, the blue smoke from exhaust problem is more likely to occur.


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