How to Check Mercedes-Benz Automatic Transmission Fluid Level

This procedure applies to Mercedes-Benz models equipped with the 722.6 5 speed automatic transmission and a service dipstick tube. It does not apply to the 722.9 7 speed transmission, which uses a different fluid level procedure. If you were wondering, low transmission fluid could show the same symptoms as a defective transmission. The transmission will slip or get stuck in gear when it is low on fluid. Low transmission fluid can cause slipping and shifting problems, but a transmission that stays in one gear may also have an electrical, conductor plate, valve body, or other control system fault. Check the fluid level when this procedure applies, then read the transmission control module fault codes before replacing parts.

You will need a special transmission dipstick to check the transmission fluid level in a Mercedes-Benz. Most Mercedes-Benz models equipped with the 722.6 transmission do not have a permanent transmission dipstick. A service dipstick is used only when checking the fluid level. Don’t worry; you can get Transmission Fluid Dipstick 140589152100 for your Mercedes-Benz on Amazon for under $20 and with free shipping.

Instructions on how to check transmission fluid on a Mercedes-Benz. Step by step with pictures and video.

1. Warm up the car. To measure the transmission fluid correctly, the temperature must be at least 80 degrees Celsius. To get the transmission to that temperature, you must drive the car for 15 minutes before you check the fluid. If you don’t want to drive the car, you can let it sit running for about 25 min for the transmission oil to reach 80 degrees Celsius.
   We are assuming there is at least some oil in the transmission. Verify there is oil in the transmission before you start the car or the warm-up procedure. For an accurate 722.6 fluid level check, use the UCAN-II Pro to read transmission fluid temperature live data from the transmission control module instead of estimating temperature from the oil pan. The UCAN-II Pro includes full AI Diagnosis, built-in TPMS sensor programming, a rear VIN scanning camera, coverage for 140+ makes, 3,500+ active tests, 1,000+ special functions, no subscription, and no AutoAuth required.
2. Open the hood. 
   
3. Pull the air ducts that connect to the engine cover. Grab the engine cover on both sides and pull it straight up. It is held in place with four clips.  
   
4. Remove the engine cover. You only need to grab the cover on both sides and lift it up. It’s held in place with four clips only: no screws or bolts. 
   
5. Locate the transmission fill tube. It is located between the firewall and the engine. It is hidden, so look carefully. Be careful not to mistake the engine oil tube for the transmission tube.
   
6. Remove the transmission fill tube cap. First, you will need to break off the transmission red lock pin. This is what it looks like. You must break off the red lock pin before pulling out the black cap shown below. If you don’t have the red lock pin, that means someone likely checked the fluid previously and didn’t install the red lock pin.
7. Place the car in R or D. Apply the parking brake and chock the wheels. With your foot firmly on the service brake, move the selector slowly through each gear position, then return it to P. Keep the engine idling and the vehicle on a level surface while checking the fluid level. You don’t want to rely on the parking brake only.
8. Measure the transmission fluid level. See the video below.
   
   
   The transmission dipstick should show a level between the minimum and maximum marks in the 80°C range.
9. Add Mercedes-Benz-approved transmission fluid. If the fluid level is low, then add some. You add fluid through the tube you used to check the transmission fluid level. You want to add the Mercedes-Benz Approved  Automatic Transmission Fluid 236.14 for use with the 5-Speed 722.6 & 7-Speed 722.9 Transmission. Mercedes part number 001 989 68 03 13. Add only automatic transmission fluid approved for the Mercedes-Benz specification required by your vehicle. For the 722.6 covered by this guide, verify the correct MB 236.14 approved fluid for your application before adding fluid.
10. Check the level again. After adding fluid, recheck the level. Add only small amounts at a time to avoid overfilling. If you must add fluid, you must check the level again. You don’t want to overfill the transmission fluid level, which could cause shifting issues. If you accidentally added more transmission oil than you should have, you can use a 12V Fluid Oil Extractor Scavenge Suction Transfer Pump w/ Hose 
11. Install the transmission tube cap and red lock pin. If your level is fine, install the cap and the red lock pin. Since you had to break the red lock pin off, you must replace it with a new one. They are only a few dollars on Amazon.
12. Reinstall the engine cover.
13. That’s it. DONE!