Why Check Transmission Fluid When Engine is Running? Explained

Do you believe in the regular inspection of cars to save them from costly mechanic consultations? If yes, you must know the running engine’s effect on the transmission fluid to obtain a correct reading. This article explains why check transmission fluid when engine is running. 

What is Transmission Fluid? ATF( Automobile Transmission Fluid) is different from engine oil and serves as a lubricant for all the components that involve a seamless car’s transmission system. The primary purpose of hydraulic fluid is to supply power for driving and enhance transmission performance.

This article deals with the reason why it is necessary to check the transmission fluid when the engine is running. In addition, how to check the hydraulic fluid and symptoms of overfilled fluid on transmission are extra information.

Why Check Transmission Fluid When Engine is Running?

Transmission fluid does not follow the same paths of checking its level as engine oil. As the purposes of both are different, so is the checking. Engine oil is checked after five minutes of its shut off. 

Conventional Method vs. Honda Cars

In comparison, the transmission fluid involves various circumstances, such as keeping the engine off and on. Most automobiles follow the conventional method of obtaining the correct reading when the engine is hot. In contrast, Honda cars are compulsive to check when the engine is warm but not running

Specifics for Checking Transmission Fluids in Honda Cars

Unlike conventional automobiles, Honda automobiles do not follow the same paths of checking transmission fluid by conventional means. Although they require you to do it when the engine is warm, you do not need to run it for a few miles. 

Steps to Obtain Correct Reading

So, maintain the engine at operating temperatures by running the engine for 5-10 minutes, parking at a level surface, and shutting the engine off. The correct reading of the transmission fluid will be marked on the oil dipstick. 

Inspect the Transmission Fluid

You can check the transmission fluid when hot or cold, but the only difference is that running engines help the temperature rise and cause the expansion of the fluid. At operating temperatures, the oil dipstick allows you to obtain the correct marking of fluid levels needed for the transmission. 

In contrast, the levels may appear low as you continue to check when the engine is cold, which is obvious. The running engine does not mean you inspect the transmission fluid after a long trip. The only requirement is to check the amount at the engine’s operating temperature or the drive of 10 miles. 

Moreover, the benefit of estimating at both temperatures will provide you with the cross-check reading, and you will be guided on when to refill it.

Note: operating temperature is achieved only after running the engine for about 15-20 minutes.

Checking Hydraulic Fluid

Running engines help the temperature rise and cause the expansion of the fluid. Therefore, inserting a dipstick will result in the correct amount. On the other hand, at cold temperatures, the automatic transmission fluid level remains low, and you end up refilling it. 

Another reason for checking hydraulic fluid when the engine is running is that the fluid is in a rotating position in all the components; the level is higher in the torque converter than the pan and helps estimate the exact level before changing it.

How to Check Transmission Fluid?

Check Transmission Fluid

Checking transmission fluid is the same as doing regular vehicle maintenance without any intervention from the expert. The need to learn a few steps and you are good to go. At the same time, the difference between the locations of car’s engine oil and other lubricants are also distinguished. 

The process begins as you park the vehicle at a level surface, turn on the engine, and wait until it gets warm up to the operating temperature.

1. Search for Dipstick

Open the car hood and search for a red, yellow, or pink colored ring. The dipstick possesses a protruding handle for clear indication and is located near the transaxle of the front-wheel drive. If you own a rear-wheel drive vehicle, look for the dipstick handle near the rear engine.

2. Estimate Fluid Level

The next step leads you to pull out the dipstick and clean it. Ensure to dip it inside the reservoir to inspect the condition and the two levels marked by hot or cold. If the fluid appears pinkish or clear and does not produce a burnt smell, you do not have to change it. 

Since you are checking the transmission fluid level when it is warm, it’s likely in the hot area of the dipstick rod. If you find fluid below the hot region, add more transmission fluid to the required level. 

Transmission fluid is vital to drive the car smoothly. Low transmission fluid will only result in leaks and create problems in accelerating. If refilled repeatedly beyond the requirement, overfilling can cause fluid foam, and instability is the only outcome.

Do you Leave the Car Running when Adding Transmission Fluid? 

Adding or checking the transmission fluid depends on what the owner’s manual instructions highlight. To add transmission fluid, you need to check the correct level, which is done by warming the engine.

Adding Transmission Fluid

Generally, it is advisable to leave the car in a running position to check and add the fluid. If checked is cold, adding extra fluid will result in overfilling and cause various damages like foaming and pressure on the transmission, which will result in venting all the fluid.

How to Check Transmission Fluid without a Dipstick?

Without a dipstick means, you own a sealed transmission vehicle. When you open the hood, there will be no colored handle for your assistance. However, there are three locations to assist you in inspecting the correct amount of transmission fluid according to specific models. 

  • Inspection plug on the side of the transmission case
  • Fill the plug on the top of the transmission case
  • Fluid checked at a specified temperature 

The need is to follow the instructions in the owner’s manual for proper guidance.

What are the Symptoms of Too Much Transmission Fluid?

As you already know, excess of everything is bad, and too much transmission fluid indicates several transmission problems. The most prominent among them are:

Unwanted Noise

The transmission noise is the prominent yet unnoticeable symptom of the high fluid level. Why? The engine creates louder noise than the transmission; thus, the strange noise due to gears grinding remains ignored. The only solution to resolve the issue is to check the fluid before every refilling.


Overfilled transmission fluid becomes the cause of leaking. A high fluid level will pressure the gaskets and force the fluid to leak, which may result in the loss of hydraulic power.

Gear Slipping

When the fluid level becomes high, the gears do not have time to mesh correctly. The result is prominent in slow acceleration or facing problems during gear changing. You can drain out the extra fluid and solve the problem.

Engine Overheating

Too much transmission also causes the engine to overheat. In these situations, it is recommended to shut the engine off and wait until it gets cool down. Check the fluid level before initiating driving. 

Summing Up

Know the importance of checking the transmission fluid when the engine is running, but the reason behind this phenomenon still needs to be clarified. This article explains the logic of engine running to know the transmission level fluid. Moreover, you will also learn what to do when a dipstick is unavailable.

Frequently Asked Questions

How Often Should You Change the Transmission Fluid?

Whenever you notice the color has turned from pinkish-red to brown, it indicates the transmission fluid needs to change. If comparing the fluid condition to the distance, you opt for changing it after running for every 30.000 to 60,000 miles.

Does Transmission Fluid read High when Cold?

Fluid needs a high temperature to expand. When you do not estimate it at operating temperature, there is a chance of getting false readings. Moreover, the dipstick is obliged to make you read the transmission fluid low.

How Long Does It Take Transmission Fluid to Warm Up?

Transmission fluid is best checked when it expands at operating temperatures. You must start the engine and let it take some time of 30 to 60 seconds to rotate the fluid in all the components part. You can quickly check the fluid level by leaving the vehicle on a level surface.

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