How to Fix Low Engine Compression


Aug 18th, 2020

How to Fix Low Engine Compression

Now let’s talk about solutions on how to fix low engine compression. We will also guide you on how to check low compression without a gauge.

Vehicles with internal combustion engines are powered by the energy obtained from combustion in the engine cylinders. A precise mixture of air and fuel is compressed before being ignited, and the combustion process that takes place provides the energy to make the vehicle move. In a few cases, however, some issues may affect or hamper the combustion cycle.

If you notice unusual signs like engine misfires and reduced fuel mileage, start considering a problem with compression, specifically low engine compression. Since other issues may show the same symptoms, it is imperative to determine if it’s low engine compression or another problem. You need to do a compression test to confirm the issue, and if it points to low engine compression, you’ll need to fix the issue as soon as possible.

Can you fix low engine compression?

Fortunately, low engine compression is not a highly complicated problem, and you can possibly fix it. But first, you need to understand the various causes of low compression in an engine. Restoring engine compression in all cylinders is tedious and time-consuming. 

If the test shows all cylinders have low compression, then fixing it is out of your hands. The best alternative is to call a professional mechanic. On the other hand, if the problem is only in one cylinder, then you can easily fix it. 

How do you check engine compression without a gauge?

As mentioned before, the signs of low engine compression can also point to a different issue. This is the reason why you need to diagnose low compression in the engine. Here is how to go about:

1. Inspect the timing belt

If you notice signs of low compression, the first step is to inspect the timing belt. Often, the timing belt is the culprit of low engine compression in all cylinders.

2. Pour oil into the cylinders

If the timing belt is not worn-out or broken, then move to the engine cylinder. Pour some oil into the cylinders and observe for any changes. If the compression goes up, the piston rings were likely stuck in one position. The oil helps move them, thus increasing compression.

3. Remove oil cap

With the engine still running, remove the oil cap to check the pressure when the engine is running. If you feel over-pressure, sometimes accompanied by smoke, it is highly likely that you have a compression leak. 

To fix this, you’ll have to repair the affected area or replace the piston and the piston rings depending on the extent of the damage. However, if everything seems to work properly, you’ll feel an under-pressure when the engine is idle.

4. Carry out a leak-down-test

The next step involves using a leak-down-tester to determine where the compression is leaking. First, ensure the camshaft is at the point where the valves are shut. Apply pressure into the cylinder and listen keenly for any compression leaking. It could be leaking into the crankcase, intake, or exhaust. If you hear any leaks, then you have low compression in that cylinder.

How to fix low engine compression

This is the last and most involving part when dealing with a low compression problem.

1. Confirm that you have low compression

Before you start tinkering with any engine components, confirm that your vehicle indeed has low engine compression. Otherwise, you will only be wasting your time and may even end up damaging some engine components. Use a compression tester to confirm, and once you’re sure there is a low compression issue, start checking for its cause. 

2. Find the cause

Start by checking the parts involved in compression. Physically examine all the parts from the cylinder to the camshaft for any damages. 

3. Repair or replace the problematic part

Repair or replace the part that has an issue. If the location of the damaged part is accessible to you, you can repair it yourself. However, if the damage is inaccessible to you or requires a replacement, it is best to leave it to a professional.

Most repairs associated with the engine are challenging and need the help of a qualified mechanic. This is because they involve taking out the whole engine when making repairs. 

4. Take your vehicle for a test drive

Once you (or the mechanic) are done with the repair, test drive the vehicle. This is necessary to ensure that the low compression issues were already fixed.

When taking the vehicle for a drive, evaluate its performance while checking for any signs indicating low engine compression. If everything is okay, you may repeat the compression test to be sure. 

On the other hand, if the symptoms persist, then you probably have another problem with the engine. You’ll need to book an appointment with a mechanic to identify and fix the low engine compression issue or possibly another problem.

How much does it cost to fix low engine compression?

Fixing low engine compression issues involves repairing or replacing the part(s) causing the problem. If you decide to have a professional mechanic do the compression test, it’ll cost you anywhere between $100 and $200. 

You’ll also need to factor in the cost of repairing or replacing the damaged part(s). While others aren’t as expensive, some are. If the problem lies in piston rings, for instance, you’ll incur $2,000 to $3,500. Head gasket repairs cost between $1,000 and $2,000, whereas a broken cylinder will set you back up to $8,000. 


Low engine compression lowers your vehicle’s overall performance. The good news is, it is not a death sentence, and one can fix it. If you’re not sure how to handle the issue, you can reach out to a qualified mechanic to help you out. 

You can alternatively do the repairs or replacement in your garage if you have the right skills and feel confident about it. If you need replacement parts, you can use our service to locate the parts you need.

By Sam O.