This week we had to fix a Mercedes-Benz that was overheating. The problem was the upper radiator hose. It turned out that a bad engine leads to the radiator hose to stretch too much and eventually fail.
The engine mounts on these cars are oil-filled. Around 100k mile range they fail. Most owners don't even realize that they have failed engine mounts. The most common symptom of bad engine mount is engine vibrations felt on the steering wheel or seat when the car is in Drive.
The radiator hose pulled out of the radiator due to the bad engine mount. The engine then lost most of the coolant and started to overheat.
Replacing the radiator hose is a very simple procedure and takes less than 20 minutes. If you have looked at the radiator hose on Mercedes-Benz M272 and M273 engines you can see why it's so simple.
A failed engine mount allows the engine to jump up under hard acceleration. This excessive jump pulls the upper engine house which eventually gets damaged and will eventually pull out of the radiator.
Replacing the radiator hose simple. Follow these instructions.
- Allow the engine to cool down then open the hood.
- Remove the air intake hose on driver's side.
- Remove the radiator hose by pressing on the C clip and pushing it slightly out.You don't need to completely remove the C clip. On the engine side, the hose is connected with another C clip or with a clamp. C clip is used on E-Class for example while on CLK550 there is a clamp.
- Connect the hose on the engine side first.
- Insert the coolant hose in the radiator port making sure it is fully inserted. Once it is inserted press the C clip to lock the hose in place.
- Add engine coolant to bring the level between the min and max mark. You check the coolant level by looking at the marks on the expansion reservoir.
This guide is applicable to most Mercedes Benz models with the 350 and 550 engine such as E550 CLK550 ML550 CLS500 E350 SL550 and many models.