How to Install a Mercedes Benz Engine Heater


1. Remove the radiator cap. On turbo diesel models, the cap is fitted to the expansion tank located on the passenger side fender well. Locate the plastic drain plug on the bottom of the radiator.
2. Place a suitable container below the radiator and remove the drain plug by turning it counterclockwise with a large flat screwdriver. Allow the radiator to drain completely.
3. Inspect the rubber seal on the plastic radiator drain plug before screwing it back into place. If the washer is worn or cracked, replace the plug and washer with a new one.
4. Undo both radiator hose clamps with a Phillips screwdriver. The upper hose connects to the thermostat housing inlet bolted to the top of the engine block; the other end of the hose connects to the bottom of the radiator. Remove the hose and lay it on one side.
5. Scrape the hardened layer of grime off the male hose connections on both the radiator and thermostat housing with the tip of a flat screwdriver. Finish cleaning the connections with a wire brush until the surfaces are smooth.
6. Place hose clamps over both hoses protruding from the aftermarket block heater. Push the end of the lower hose over the radiator inlet pipe and fit the upper hose onto the thermostat housing outlet.
7. Inspect the position of the heating element between the two hoses to ensure that it clears the side of the radiator. If not, loosen the central hose clamps and adjust the heating element for adequate clearance. Tighten all four hose clamps securely with a screwdriver.
8. Route the power cord leading from the heating element to a convenient location under the hood.
9. Refill the radiator with coolant and inspect all hose connections for leaks. Inspect the rubber seal on the radiator cap. If it is cracked or perished, replace the radiator cap with a new one.
10. Plug the block heater power cord into a three-prong wall outlet. Leave the unit switched on for a few minutes before touching the upper hose to ensure that the heating element is working properly.
11. Remove the power cord from the electrical outlet. Fold the cord and wrap elastic band around the loops to hold them together. Secure the cord at a convenient location under the hood with a short length of nylon string.