Replacing Thermal Paste Behind Mercedes Benz EZL Unit

Need to replace the thermal paste on your Mercedes-Benz EZL unit? Learn how to replace the thermal paste by following the procedures below.

The factory used a thin layer of white thermal paste between the bottom of the EZL unit and the inner fender so that heat generated by the EZL could be transferred to a larger and cooler area.

I read about this for a while before I jumped in and replaced it; Mercedes Benz recommended replacing it every ten years.

During the years, the thin layer tends to dry up and flake off the EZL, reducing its ability to transfer heat to the body of the car; this will cook the ELZ parts from the inside. 20-30 minutes of your time will save an expensive part with less than $10, or if your EZL is on its last leg, that will add maybe a couple of years to its life before it completely dies.

What you will need

Thermal paste: I used “Super Thermal Grease II” from MG Chemical. I bought it from an electronics store outlet for $8.
Rubber gloves
Any solvent of your choice to clean the EZL
Paper towels
Razorblade
10mm socket
Food wrap

Instructions

Carefully remove the electrical connectors and one vacuum connection from the EZL and fold them aside. So they are out of the way.
Loosen and remove the three nuts that secure the EZL to the car’s inner fender.
Clean the inner fender-well area, as well as the back of the EZL, using a good solvent. I used my wife’s nail polish remover and left it open, and she is mad right now; that thing evaporates so fast; use your razor blade to scrape the excess for the hard dried stains lightly. Be careful not to clean the face of the EZL with the solvent because that will erase the bar code and the model … etc. of the EZL.
Spread a layer of thermal paste on the back of the EZL. You want the layer to be 1-2mm thick — no less or no more.
I found out that when you buy a new EZL, there is a film to protect the paste, I checked online, and everybody used food wrap instead during the past years. It will disintegrate by age, heat … etc. The film is still there on my EZL, and the film is in good shape, so I think it has been replaced during the last five years as I don’t believe this is a 30+ years past film. Use your old film if yours is worth saving; I checked with three different electronic stores in Houston (Micro Center, Houston electronic outlet, and Fry’s) they confirmed that there is nothing these days called “Thermal conductive film.”

The thermal paste developed throughout the years; they also said that it’s only to prevent making a huge mess with the paste while working on the vehicle at the factory when they assembled the vehicles. Still, I believe since the part is not a Mercedes Benz part, it’s Bosch manufactured by Siemens. They used that film to protect the paste while shipping the part to MB warehouses. It’s your call to use a wrap from not. Nothing will happen if you don’t know the history of your EZL; just go ahead and replace it. Better than being sorry later.
Trim the wrap access using a blade; do not disturb the thickness of the paste, and carefully smooth it with your fingers.
Re-install the EZL onto the car’s inner fender using the exact reverse of the removal process.

The 104 engine service manual says in section 15-2093 – Removal and installation of EZL/AKR ignition control module.

Heat conducting paste has been applied to the rear of the control module and covered with heat-conducting protective foil for improved heat dissipation. The protective foil must not be removed.

We hope you find the Replacing Thermal Paste Behind Mercedes Benz EZL unit guide helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.