Mercedes-Benz E-Class and E-Class AMG: How to Check Transmission Fluid

This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009).

For a couple of reasons, Mercedes-Benz does not want their customers to check the transmission fluid level on their vehicles. The reasons include, but are not limited to:

1. Mercedes-Benz defines the transmission fluid as “lifetime fill.” As a result, there is no reason in their minds for a customer to check the fluid level.
2. Transmission fluid level is critical to both good shift quality and long-term durability of the transmission. Improper fluid level can, and does, break a transmission or, in a worse case scenario, cause a fire.
3. Transmission hydraulic fluid has a high coefficient of thermal of expansion. This means the volume of fluid grows a lot as it heats up. This makes the fluid temperature a critical variable when checking the fluid level.
4. The hydraulic systems in modern automatic transmissions do not like dirt. So, it’s best not be sticking dirty dipsticks into the fluid. Mercedes-Benz engineers know this and discourage customers from checking the transmission fluid level.

If you believe you need to check the transmission fluid and you don't want to spend the money on a professional, here's how to do it yourself.

The Mercedes-Benz E-Class' transmission does not have a dipstick; you’ll have to buy one. The transmission fill tube cap has a small locking tab on it to keep prying hands away. The tab is to be removed in order to take the cap off of the transmission fill tube. It’s best to have a cap and locking tap on hand in case you break something or lose a part; it’s cheap insurance.

Step 1 – Drive the car and allow the engine to reach operating temperature

The engine being at "normal operating temperature" ensures the transmission fluid is at the proper temperature to check the level. The transmission fluid temperature should be at 175 degrees F for an accurate level measurement.

Step 2 – Set the car on level ground

The car being on level ground is critical. The transmission MUST be at its "level" installation angle in order to get an accurate level measurement.

Step 3 – Leave the engine running

This ensures the transmission pump is running and the transmission’s hydraulic system is filled with fluid.

Step 4 – Find the transmission fill tube

It has a black cap and is behind the engine just in front of the fire wall and behind the engine cover. Don’t confuse this transmission fill tube with the engine oil tube in the front of the engine!

Step 5 – Remove locking tab

Remove the plastic locking tab by breaking off the tab on top and pushing the tab through the cap. Remove the fill tube.

Step 6 – Make sure the dipstick is very clean

Cleanliness is very important inside a transmission. Insert the dipstick down the transmission fill tube. You may feel some resistance as the dipstick snakes its way down the fill tube. Also, because the dipstick is flexible, it can be difficult to know when the tip of the dipstick is touching the bottom of the transmission fluid pan.

Step 7 – Stop when it hits

This is the point where you get the transmission fluid level in the transmission. The dipstick will not go all the way into the fill tube. There is approximately 6” of the dipstick visible when the tip of the dipstick is touching the bottom of the transmission pan.

Step 8 – Slowly remove the dipstick and look at the tip

Is the fluid up to the middle of the red portion of the dipstick tip? That is the correct fill level for this transmission at 175 degrees F oil temperature and with the engine running.

Step 9 – Repeat steps 5, 6 and 7

Repeat Steps 5, 6 and 7 at least three more times until you’re satisfied with your work and just to make sure the levels are correct.

Step 10 – Finish up

When you're satisfied with your work, re-install the transmission fill tube cap and the cap locking tab.

Related Discussions

• Transmission Fluid Maintenance Question - MBWorld.org
• Checking and Adding Transmission Fluid - MBWorld.org