Bubbles in Transmission Fluid (Causes & Fixes)

Hasan Amjad
Bubbles in Transmission Fluid

If you’ve noticed performance issues with your vehicle’s transmission, bubbles in the transmission fluid may be at the root of the problem. But do you know how bubbles form inside the transmission?

The bubble theory is simple for fluids. Bubbles are formed whenever air gets captured inside the fluid. So, air somewhere enters the transmission system and creates bubbles in the transmission fluid.

Likely, that’s due to air leaks in the system, corroded seals, solenoid contacts, and underfilling or overfilling of the transmission fluid.

As we proceed in this article, we will delve into how each factor contributes to bubble formation in the transmission fluid and provide practical solutions to address and rectify these issues.

Why Bubbles are Formed in Transmission Fluid [6 Major Reasons]

Transmission fluid has four primary functions, lubrication, cooling, power transmission, and cleaning. It acts as a lubricant for the various moving parts within the transmission, such as gears, bearings, and clutches.

Furthermore, it helps to dissipate friction heat, preventing the transmission from overheating and sustaining damage.

Moreover, the transmission fluid has additives that help clean and protect the transmission’s internal components.

When a bubble forms inside the transmission, the smoothness and somehow the working of the transmission system. Moreover, this is also a sign of some underlying issues within the transmission.

Let’s explore the reasons why bubbles are formed:

car mechanic fixing car

1. Leaks Within the Hydraulic Seal

As mentioned earlier, air is the main ingredient for bubble formation. Now, the best entry for air is hydraulic system sealing points, which normally maintain the pressure of the whole system.

Over time, as the vehicle ages, the rubber seals corrode and allow air to enter the transmission fluid. When a seal leaks, it causes the fluid pressure to drop, leading to turbulence and air bubbles in the fluid.

Fix: Inspect your vehicle; you may see signs of a fluid leak. It is usually reddish brown. Look for the leaking points and replace their respective seals. However, there are chances you won’t be able to trace that. So, I recommend taking the vehicle to a hydraulic professional.

2. Incorrect or Low-Quality Transmission Fluid

Using the wrong type of transmission fluid or a low-quality fluid can contribute to the formation of bubbles in the fluid.

Some fluids may have inadequate anti-foaming properties or be incompatible with your specific transmission system, leading to increased aeration.

If you have recently replaced your transmission fluid and you’re witnessing transmission issues, like difficulty in gear shifting, or overheating. Likely, the fluid you used isn’t compatible with your current transmission.

Fix:  Drain the existing fluid and replace it with the correct type and high-quality transmission fluid specified by your manufacturer. Buy it from a reputable manufacturer to ensure optimal performance and protection for your transmission system.

3. Overfilled Transmission Fluid

Overfilling is another source through which the fluid can catch air.

When the fluid is overfilled, the increased volume can cause it to become more turbulent as it moves through the transmission. This turbulence promotes the formation of air bubbles, which can then become trapped in the fluid.

Fix: Check the transmission fluid level using the transmission dipstick and drain the excess fluid to reach the recommended level.

4. Worn or Damaged Transmission Components

Other than seals, worn-out transmission components, such as gaskets, or bearings, can allow air to enter the transmission fluid, creating bubbles.

When any of these components is damaged, it drops the transmission system pressure and creates an opening through which air can likely enter. These bubbles can then compromise the fluid’s lubricating and cooling properties and cause transmission problems.

If you’re hearing a noise within the transmission system, having difficulty shifting gears, or there’s a burning smell. Chances are that the faulty transmission components are behind this.

Fix: Get your car to the garage for a thorough transmission examination. They will inspect it, empty the fluid and replace the faulty parts.

5. Clogged Transmission Filter

A clogged transmission filter or cooler can restrict fluid flow, causing the fluid to become aerated and form bubbles. A dirty filter can also cause the transmission to overheat, exacerbating the problem.

Fix: Replace the transmission filter and flush the transmission cooler to ensure proper fluid flow and reduce the likelihood of bubbles forming.

6. Corroded Solenoid Contacts

Solenoids are electromechanical valves that regulate the flow of transmission fluid.

Due to moisture, the contacts can get rusted and corroded over time. The flow regulation is affected when that happens, and the fluid can get aerated with bubbles.

Fix: Diagnosing the issue with solenoid contacts can be hard. So, I suggest you take the vehicle to a technician for a thorough inspection.

Are bubbles in the transmission fluid dangerous for the car?

Bubbles in transmission fluid, or aeration or foaming, can cause problems for your vehicle’s transmission system. If not addressed promptly, these bubbles can lead to erratic shifting, slipping gears, overheating, and even transmission failure.

To prevent further damage to your vehicle, it’s crucial to identify the causes of bubbles in transmission fluid and apply the appropriate fixes.

How to Prevent Bubble Formation Within The Transmission Fluid? [Preventive Measures]

Preventing bubble formation within the transmission fluid is essential for maintaining optimal transmission performance and preventing future issues.

Here are some preventive measures you can take to prevent bubble formation:

  • Regularly check the transmission fluid levels and top off the fluid to prevent the formation of bubbles due to low fluid levels. It is recommended to change it after 40,000 – 60,000 miles.
  • Use high-quality transmission fluid compatible with your specific vehicle’s transmission system. Consult the owner’s manual or a professional for recommendations.
  • If you notice any leaks within the transmission system, address them immediately to prevent further fluid loss and potential bubble formation.
  • Avoid exposing the transmission system to extreme conditions, such as excessive heat or overloading, which can cause increased wear and tear and contribute to bubble formation.

Frequently Asked Questions

How to check transmission fluid level?

To check the transmission fluid level, park the vehicle on a level surface and turn on the engine. On car idling, locate the transmission dipstick and pull it out. Check its level based on “full” and “low” marks on it.

How to remove bubbles from the transmission fluid?

Removing the air is called bleeding. The best way to bleed transmission fluid is by draining all of it and then refilling it with the new fluid.

What are a few signs of low transmission fluid?

Signs of low transmission fluid include difficulty shifting gears or delayed engagement, whining or humming noises, transmission slipping or jerking, burning smell, overheating, or a transmission warning light on the dashboard.

Final Words

Bubbles in the transmission fluid can indicate various issues within your vehicle’s transmission system. Identifying and fixing issues promptly is essential for enjoying a seamless ride.

I hope this comprehensive guide has provided valuable insights into the common causes of bubble formation in transmission fluid. By following the preventive measures outlined in this article, you can maintain optimal transmission performance and prevent a potential failure.

Follow the preventive measures to ensure that your vehicle’s transmission system operates smoothly and reliably. Consult a professional mechanic if you have any concerns about your transmission system.

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