Top Causes of Low Compression In The Engine

In this guide, we will cover some of the causes of low compression in an engine and what you should do. The internal combustion engine relies on compression to produce power. The oxygen and fuel enter the combustion chamber, where combustion occurs. For the engine to function effectively, there has to be healthy and high compression. The engine’s performance depends on how much air it can compress in each cylinder.

Low compression is something no one wishes to encounter because it is expensive to fix. However, your engine might experience low compression. If this happens, you most definitely feel your engine’s power is going down. It is essential to know some causes of low compression in an engine.

Causes of Low Compression

Damaged valve seals and piston rings are some common causes of low compression. Here are other reasons for low compression which you should know.

Faulty Valves 

The primary role of the valves is to seal the combustion chamber. The combustion chamber has intake and exhaust valves, which either open or close depending on which face of stroke in the combustion chamber.

The valves seal the combustion chamber and ensure that the pressure is contained before being released into the exhaust. If any of the valves are faulty, the compression is likely to leak into the exhaust or the intake.

Damaged Piston Rings

Each piston has either 2 to 4 rings around it. The rings ensure no compression leaks into the crankcase and prevent oil from leaking into the combustion chamber. When the piston rings are worn out, the oil will leak into the combustion chamber, and you will experience a low compression. The best way of solving this is to replace your piston rings.

Damaged Pistons

A worn-out piston is another common cause of low compression in the engine. The pistons are made of aluminum alloys that enable them t withstand the high temperature in the combustion chamber. The pistons will develop hot spots when your engine runs lean or knocks. The high mileage engines also wear out the pistons, which leads to low compression.

Faulty Hydraulic Lifter

The hydraulic lifters are between the camshaft and the valves. These lifters are self-adjusted to ensure that the play between the lifter and the camshaft is okay. For the lifters to do this role, they are filled with oil pressure.

If your engine is high mileage, the camshaft may create holes in the hydraulic lifters. When such happens, the lifters cannot hold the oil pressure, and they will compress whenever the camshaft opens them without opening valves.

When the valves are not opening correctly, you will experience low compression.

Poor Camshaft Timing

A faulty timing belt or chain leads to low compression in all the cylinders. The crankshaft rotates the timing belt to transfer power to the camshaft, which controls the opening of the valves. The valves control the inflow and outflow of gases into the combustion chamber.

A faulty belt will fail to inject the air-fuel mixture at the required time, leading to low compression. 


The above are common causes of low compression, which you should know. If you experience low compression in your engine, consider consulting a professional mechanic

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