Bubbles in Transmission Fluid: Top Causes and Solutions

Bubbles in transmission fluid indicate an underlying issue with your car’s transmission. Air can get into your car’s transmission from different areas such as transmission leaks, a clogged transmission filter, or low transmission fluid.

Bubbles in Transmission Fluid ~ Ran When Parked

In this post, you will learn the causes and solutions to bubbles in the transmission fluid.

What Is the Root Cause of Bubbles in Transmission Fluid?

The root cause of bubbles in transmission fluid is a leaking transmission seal or pan gasket. With time, your car’s transmission pan seals or gasket can wear out because of heat, friction, or age. Once it happens, transmission fluid will leak from the edges and also introduce air.

As your car’s transmission fluid leaks, it results in a partial vacuum inside the transmission pan. This allows air to get inside the transmission fluid. Once inside, the air gets trapped in the fluid. As the fluid circulates, the agitation of trapped air causes air bubbles in the transmission fluid.

That said, are there air in transmission fluid symptoms? Yes, the most obvious symptom is air bubbles on transmission dipstick such as bubbles on CVT transmission dipstick.

Low Transmission Fluid: Catalyst for Air Intrusion

Another explanation for air in your car’s transmission fluid is because of low levels of transmission fluid. This arises from the way the transmission fluid interacts with the internal components, especially in automatic ones. If the car has low transmission fluid, it means there is not enough to adequately fill all the spaces in the transmission.

Root Cause of Bubbles in Transmission Fluid ~ Ran When Parked

As a result, it creates empty spaces in the transmission components and passages. Therefore, areas with low fluid levels, make the fluid more turbulent due to the presence of these empty spaces. If you are wondering – is bubbles in transmission fluid bad? The answer is yes.

The turbulence causes air to flow into the fluid through gaps, openings, or areas where the fluid is not completely sealed off from the external environment. As fluid flows through the transmission, the introduced air mixes with the fluid. This mixture of fluid and air is what creates air bubbles in the transmission fluid.

Degraded Transmission Fluid Can Result in Air Bubbles

Your car’s altered physical and chemical properties in degraded transmission fluid contribute to the presence of air bubbles in the transmission fluid. Over time, due to heat, friction, and contaminants, transmission fluid degrades.

As a result, the degraded fluid becomes thinner or thicker than its optimal state, which affects its ability to operate properly. For instance, it alters its viscosity.

This alteration changes fluid flow patterns creating areas of turbulence and eddies that trap or draw air into the fluid. The presence of air in the degraded fluid combined with the turbulence results in the formation of air bubbles.

Clogged Transmission Fluid Filter Can Unleash Air Bubbles

Another reason for the presence of air in your car’s transmission fluid is a clogged transmission fluid filter. This causes disruption to the normal fluid flow and subsequent introduction of air.

It happens over time as the transmission fluid filter clogs with accumulated debris and contaminants. Once the filter clogs, it restricts the flow of fluid through its passages.

As a result, the transmission fluid faces more resistance. This change in the normal flow of the transmission fluid results in turbulence and eddies.

It is this turbulence that introduces air into the fluid and the air gets trapped because of the chaotic flow patterns. As the fluid flows through your car’s transmission system, the trapped air mixes with the fluid. It is this mixture of fluid and air that forms the air bubbles.

Failing Transmission Pump Stirs Air Bubbles in Transmissions

If your car has a failing transmission pump, it can trigger the formation of air bubbles in your car’s transmission fluid. This happens from the pump’s inability to maintain proper fluid circulation and pressure.

In a healthy transmission, the pump usually draws fluid from the transmission pan, pressurizes it, and then directs it to the various transmission components.

However, once the transmission pump malfunctions, it loses its ability to generate enough pressure and sustain consistent fluid flow. A transmission pump can fail because of worn internal components, damaged seals, or other mechanical issues.

With time, the pump’s performance deteriorates. This makes it struggle to generate the necessary pressure to push the fluid through the transmission system. As a result, it can cause turbulence because of the uneven distribution of the transmission fluid.

The turbulence increases the likelihood of pulling air into the fluid through gaps or weak seals. Over time, the introduced air forms air bubbles as the transmission fluid circulates.

Overfilling Transmission Fluid Can Result in Bubbles

Overfilling your car’s transmission fluid can result in air bubbles in the transmission fluid. When you overfill it, you disrupt normal fluid behavior and flow patterns.

Filling your car’s fluid to the optimal level ensures proper operation, lubrication, and cooling of the transmission components. However, overfilling surpasses the manufacturer’s recommended limit. As a result, it alters the dynamics of the transmission fluid.

For instance, as the transmission operates, the excess fluid will start to churn and splash because of the limited space. The turbulence and agitation in the transmission can introduce air into the fluid. Because of overfilling, the transmission fluid can trap air in the fluid resulting in the formation of air bubbles.

Excess Heat Causes Air Bubbles in the Transmission

Excess heat in the transmission fluid can result in air bubbles. When the transmission fluid is too hot it changes its fluid properties and increases the likelihood of air entering the system.

Excess Heat Causes Air Bubbles in the Transmission ~ Ran When Parked

Your car’s transmission fluid is designed to operate in a specific temperature range to maintain its intended properties. However, the fluid can overheat because of severe driving conditions, towing heavy loads, or fluid contamination. Once it happens, it exposes the transmission fluid to excess heat.

In turn, the heat can breakdown the fluid changing its characteristics. It is these changes in fluid properties that can result in foaming as turbulence in the fluid introduces air because of the chaotic movement.

What Is the Solution to Air Bubbles in Transmission Fluid?

The solution to air bubbles in the transmission fluid is to check the fluid level and add the appropriate amount to bring it to the recommended level. Ensuring the transmission has sufficient fluid eliminates the likelihood of pulling air into the transmission fluid.

When you add fluid to the recommended level, you are ensuring the transmission has enough fluid. This way, the fluid will circulate without turbulence.

Solution to Air Bubbles in Transmission Fluid ~ Ran When Parked

Once you restore the recommended fluid level, the transmission’s internal components will function as intended. This way, you will avoid the turbulence that arises from low fluid levels creating air bubbles.

In addition, maintaining the proper fluid level helps prevent overheating the fluid which can also unleash air bubbles in your transmission fluid.

Replace Failing Transmission Seal/Gasket: A Quick Fix

Replacing a leaking transmission gasket or pan will work wonders in solving the problem of air bubbles. A new gasket will seal the transmission system properly, so nothing unwanted can get in including air.

Just like sweeping out the dust from your house, a new gasket ensures that only clean, smooth transmission fluid is circulating. You may need a professional to deal with a leaking gasket.

Replace Clogged Transmission Fluid Filter: Restore Flow

Another solution is replacing a clogged transmission fluid filter. When you replace the clogged transmission fluid filter with a new, clean filter, you restore proper fluid flow. This will eliminate the source of turbulence that introduced air into the fluid.

With a clean filter in place, the transmission fluid will flow without resistance. To avoid it in the future, replace the transmission fluid filter in routine maintenance.

Repair or Replace Failing Transmission Pump to Clear Bubbles

If your car has a failing transmission pump you can solve the issue by repairing or replacing it. Repairing or replacing the failing transmission pump addresses the root cause of the problem.

By restoring proper fluid flow, you eliminate turbulence in the fluid and ultimately the formation of air bubbles. This is another way how to get air out of transmission fluid.

Changing Degraded Transmission Fluid Can Banish Air Bubbles

Changing the degraded transmission fluid is another way of banishing air bubbles in the transmission fluid. When you swap out the old fluid with fresh, recommended high-quality fluid, you give your car a much-needed boost. Think of how a good night’s sleep refreshes you – that’s what the new fluid does for your car’s transmission.

With this rejuvenation, gear shifts become smoother and those pesky air bubbles vanish. This way, your car’s transmission does its job without hiccups.

Remove Excess Transmission Fluid to the Recommend Level

Another solution to air bubbles in the transmission is removing excess fluid. Doing so restores the fluid to the recommended level which prevents over-agitation that causes the formation of air bubbles. To remove the excess fluid, you will need a siphoning tool to extract a small volume of the fluid.

However, before siphoning, make sure the fluid is cool. Next, compare the length of the siphon tube to the dipstick to ensure it can reach the filler port. Now, insert the siphon tube into the dipstick hole or the filler port and place the other end in the drain pan.

With that in place, you now need to pump the siphon pump to draw the transmission fluid and gravity will pull it into the drain pan.

Draw out approximately half a quart of the excess transmission fluid then wait for around an hour for everything to settle. Afterward, check the level of the transmission fluid to make sure it is at the correct level. Also, check if the bubbles in the fluid are dissipating.

If after leaving the car to sit for a day or two you notice air bubbles, you may have to change both the filter and fluid.

That is how to bleed air from automatic transmission. With the right amount of fluid, the transmission works harmoniously, which prevents the fluid from getting overly excited and creating air bubbles. If you feel this process is overwhelming, you can take the car to a qualified mechanic.

Let an Expert Inspect the Transmission and Address the Issue

Letting a professional deal with the issue is another solution. Just like a doctor can spot early signs of a problem in your body, a qualified mechanic can identify issues with your car’s transmission.

A skilled professional knows where to look and what to check to find the source of these bubbles. For instance, the professional will assess the condition of your car’s valve body for signs of wear. This will help restore the fluid normal state.

Instead of guessing and hoping for the best, a professional will give you an accurate diagnosis. Similarly, the professional will recommend the solution your transmission needs – such as a fluid change, a part replacement, or a tweak in the system. Once the professional identifies the problem, fixing it will be easy for them.

Besides, when an expert is working on the issue, you have peace of mind. Thus, getting an expert is one of the best ways of eliminating air trapped in transmission.

Bubbles in Transmission Fluid Conclusion ~ Ran When Parked


In this post, you have learned the top causes and solutions of air in your car’s transmission fluid. Here are the takeaways:

  • The main cause of this issue is transmission leaks.
  • Other causes are a failing fluid pump, degraded transmission oil, low transmission fluid, or clogged fluid filter.
  • To solve this, you may have to replace the leaking transmission gasket, check the fluid level, or replace the failing fluid pump.
  • Hiring a professional is another solution.

With this understanding, you can restore the proper working state of your car’s tranny fluid.

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