Having a Mercedes serviced at a dealer can be costly, so some owners prefer to do it themselves. Changing transmission fluid is a standard service necessity, but many people postpone or forget about transmission fluid maintenance. In general, transmission fluid should be replaced every 64,000 - 130,000 kilometres, depending on the model.
It was originally believed that the Mercedes transmission did not require a fluid and filter change, but the manufacturer has since changed its stance on the “sealed for life” claim. While some feel new fluid may contaminate the old, industry standards now suggest that draining old transmission fluid and replacing it entirely helps extend the life of the car.
The instructions may vary by model, but these steps explain how to drain and refill transmission fluid for a basic Mercedes vehicle. A Mercedes special transmission dipstick is needed for this project.
Drain Old Mercedes Transmission Fluid
Before starting, the Mercedes must be jacked up and secured on stands, so there is no potential for movement during the process. The car owner must slide beneath the car to locate the transmission pan and its 5mm drain plug, which is at the bottom of the pan. The transmission holds about 10.5 litres of fluid, so a large, plastic drain pan will need to be positioned below before the plug is pulled. Extra rags and paper towels will be helpful, as this job can be messy.
A special Mercedes dipstick is recommended along with an infra-red thermometer. Follow these steps to successfully complete this project.
Step 1: Remove the drain plug
Newspaper and drain pans placed beneath the transmission pan will help prevent stains on surfaces. The first step involves removing the transmission drain pan plug with a 5mm hex socket and a ratchet and replacing the plug when the fluid has completely drained.
Step 2: Remove and clean the transmission drain pan
A 30 Torx socket is needed to remove the bolts that hold the pan in place. Once the pan is loose, the car owner can lower and slant the pan toward the drain pan to remove the remaining fluid and clean the pan and bolts. If metal bits are seen in the bottom of the pan, it may indicate progressive transmission failure.
Step 3: Replace transmission filter
The filter can be easily pulled from inside the transmission. Angling the filter toward the drain pan will ensure that any fluid falls into the pan. Once the old filter is removed, the car owner can install a new filter.
Step 4: Drain torque converter
The torque converter is located ahead of the transmission pan. The engine must be rotated in order to access the torque converter plug. A helper can turn the engine with a 27mm socket and a long breaker bar to the crankshaft pulley nut. The drain plug will become visible through the square opening. After placing the drain pan beneath the torque converter, a 5mm hex socket and extension is used to remove the drain plug. After the converter is drained, the plug is reinserted.
Step 5: Check the gasket, reinstall the pan
Before reinstalling the transmission drain pan, the gasket should be inspected. This is the perfect time to replace it if it looks old. Otherwise, put it back in place by placing it around the edge of the drain pan. A torque ratchet attaches the six bolts back in place to 1.22 m kg.
Step 6: Replace the fluid
The transmission fluid tube is located near the firewall on the left side of the engine. A long funnel makes it easier to pour 6 litres of Mercedes Benz automatic transmission fluid into the tube. Driving the car around the block a few times helps heat the fluid to the basic operating temperature. After parking and leaving the car in idle, a quick temperature check with an infra-red thermometer helps car owners ensure that fluid temperature is at 80 degrees Celsius.
Step 7: Check the new fluid
The fluid level can be checked with the special Mercedes Benz dipstick by pushing the dipstick down to the very bottom of the transmission drain pan and removing it. The perfect measurement is at the 80 degrees Celsius mark. If the fluid level is below the mark on the dipstick, then add more. If it is too high, then the excess should be drained.
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