Blue engine smoke
You’ll probably notice your car misfiring when you turn the keys in your ignition, or find your vehicle shakes more than usual when idle. Since blue and grey smoke coming from your exhaust can point to the same faults, there is naturally a bit of overlap with the above section. These leaks are caused by:
1. Worn pistons and piston rings
Pistons use rings to keep an air tight seal in the cylinders of a combustion engine. After some wear and tear, the rings can leak oil into fuel which eventually burns as blue smoke. Although this usually escapes from the exhaust it can appear from the bonnet too
2. Damaged valve stem seals
Valves regulate the amount of fuel and air mixture allowed into cylinders for combustion. Although their seals are usually made from high-strength rubber, they can become cracked and worn by extreme temperatures or wear and tear. Mechanics will often use special tools to compress the valve spring before replacing a valve seal.
3. Malfunctioning PCV valve
A PCV valve or Positive Crankcase Ventilation valve releases exhaust gas and unburned fuel from the engine block. If the PCV valve gets stuck, it will mix oil, air and other gases inside the engine. The combustion of this mixture will cause blue smoke. Fixing a PCV valve shouldn’t be too costly and usually involves a replacement rather than a repair job.
4. Worn engine oil seals
As oil travels from the tank around the engine it relies on a number of seals to prevent it from leaking to other areas of the car. These seals can suffer from wear and tear, leading to leaks and oil burning off as blue smoke. If you notice any blue smoke or oil spillages, visit a trusted garage as soon as possible.
5. Inlet manifold leaks
The inlet manifold supplies a mixture of fuel and air to cylinders in the engine. If the manifold leaks oil into the cylinders, this can burn as blue smoke. Sealants are available to help patch up small leaks but may only work as a temporary fix. Enlisting the help of a professional is always your best option.
6. Head gasket failure
Head gaskets are responsible for sealing the internal combustion process and can become damaged through overheating, allowing oil into different parts of the engine.