5 Causes of Low Compression in an Engine

(Updated on January 28, 2020)

The internal combustion process involves mixing gasoline and air inside the engine’s cylinders. This is what is known as engine compression. Each cylinder of the engine must have the right amount of compression if the combustion process is going to work out properly.

If the compression ends up being too low in any of the cylinders, then your vehicle will not be able to drive normally. Then you will notice your engine performance is significantly reduced, making it difficult to accelerate and drive the car as usual.

If you were to not have compression in all cylinders, then you would not be able to start your car at all.

Top 5 Causes of an Engine Losing Compression

If you notice any symptoms of low car engine compression, the next step is to figure out what caused your engine to lose compression in the first place. Below are the top 5 reasons for low engine compression.

1) Timing Belt is Bad

The crankshaft and camshaft are attached by the timing belt. This is how they are able to turn properly. If you have a damaged timing belt, the camshaft won’t allow the intake and exhaust valves to open and close the way they’re supposed to.

This means the cylinders won’t have any combustion taking place, so no gases will come out. Low compression is the result of this.

2) Piston Damage

Engine cylinders contain pistons made of aluminum alloy. This material is designed to sustain the combustion power of the engine. But if the engine gets too hot and starts to overheat, then the piston will develop hot spots in its alloy material.

If the extreme heat does not go away, the hot spots will turn into holes. This will cause fuel to flow out of these holes. With less gasoline in the cylinders, you will have low compression.

3) Piston Rings Damaged

Your piston rings will become damaged if there is too much heat exposure on them. These rings are what prevent carbon gas from getting out of the cylinder.

If the rings are damaged, then the gases will come out. Then, you will have an engine with low compression.

4) Valves Leaking Gas

All the cylinders in an engine have intake and exhaust valves. The intake valve is where fuel and air flow into before they enter the cylinders. After they’re mixed together, the combustion process takes place and causes exhaust fumes to come out of it.

These fumes pass through the exhaust valves at just the right time. But if the valves endure too much heat, then fuel will come out of them instead. This will result in low compression.

5) Faulty Head Gasket

The head gasket exists on the cylinder head area. This is another component which helps keep carbon gases trapped in the cylinder.

But if the head gasket were to get damaged or go bad for some reason, there may be a gas leak resulting from it. Once again, low compression will occur from this.

Tips to Inspect Low Compression

If you suspect that you have low engine compression, you need to use a compression gauge to verify this. It will take about 45 minutes for the gauge to give you an accurate response as to whether there is low compression or not.

If you are unsure about how to use a compression gauge or you don’t own one at all, then just take your vehicle to the nearest auto repair shop and have them perform the compression test.

If the results show that you do have low compression in the engine, then there is probably damage to one of the critical components of the engine.

Check the pistons, gaskets, cylinders, and valves to see if they’re in good condition. If they are not, then replace them immediately. The cost of replacement will be considerable because of the many hours of labor that will be needed.

2 thoughts on “5 Causes of Low Compression in an Engine”

  1. My Toyota is hard to start morning. But after minuts it starts running. Working for hours and never start after parking.what is the issue?


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