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Pelican Technical Article:

Radiator Hoses Replacement

Kerry Jonsson

Time:

3 hours3 hrs

Tab:

$50

Talent:

**

Tools:

Flathead screwdriver, pliers

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Upper radiator hose, lower radiator hose

Hot Tip:

Work on a cold engine and drain the engine coolant first

Performance Gain:

Replace damaged or soft hoses before they fail

Complementary Modification:

Change thermostat and flush cooling system

While your engine is running it generates power and torque that is applied to your driveline and propels the car. As a byproduct of generating power the engine also produces heat. This heat must be removed before it can damage internal engine components. The job of your cooling system is to remove this heat. It does this by using a coolant pump to circulate hot engine coolant from the engine block to the radiator, where air passing through it absorbs the heat and cools off the coolant. This process is repeated to maintain an acceptable engine temperature.

The engine block vibrates and moves around a little bit on the engine mounts as the engine produces torque. The radiator is attached to the body of the car which does not move around with the engine. This means any wiring, lines or hoses need to be flexible if they are going to connect from the body to the engine. Radiator hoses are flexible and allow the engine to move around a little bit while the radiator stays fixed to the body. They also seal the cooling system and pass the hot coolant from the engine to the radiator, to get cooled off and also from the radiator back to the engine block to repeat the process. Over time radiator hoses can get soft and/or dry out and crack. A cracked hose will allow coolant to leak out of it and eventually lead to an "over-heating" condition. Soft hoses are also a problem. Cooling systems are pressurized to raise the boiling point of the coolant. This pressure can reach as high as 15psi on a normal engine. This pressure can act on a soft hose and eventually cause it to blow apart causing a sudden loss of coolant. This can leave you stranded on the side of the road. In this tech article I will go over how to replace your radiator hoses.

Engine coolant can get over 212 degrees (100 degrees Celsius) while the engine is running. Never open a hot coolant reservoir. The system will depressurize and hot coolant can come pouring out and burns your skin. If you are going to do this job make sure the engine is fully cooled off before attempting to remove the coolant reservoir cap.

This picture illustrates under the left side of the car towards the front of the engine compartment with the front cover removed.
Figure 1

This picture illustrates under the left side of the car towards the front of the engine compartment with the front cover removed. Locate the radiator drain plug (green arrow).

Have a drain pan ready underneath where you are working.
Figure 2

Have a drain pan ready underneath where you are working. Rotate the drain plug counter clockwise to loosen it and thread it out all the way. It will not come out of the radiator but it will allow the coolant to drain out of the radiator.

This picture illustrates the engine compartment towards the front of the engine.
Figure 3

This picture illustrates the engine compartment towards the front of the engine. On the upper radiator hose use a flathead screwdriver to lever down on the spring clip (red arrow) for the bleed line hose.

Twist the bleed line hose to break loose the seals.
Figure 4

Twist the bleed line hose to break loose the seals. Then pull it straight out of the upper radiator hose.

Using a flathead screwdriver, loosen the hose clamp on the engine side of the upper radiator hose.
Figure 5

Using a flathead screwdriver, loosen the hose clamp on the engine side of the upper radiator hose.

This picture illustrates the radiator side of the upper radiator hose.
Figure 6

This picture illustrates the radiator side of the upper radiator hose. Use a flathead screwdriver to lever out the retaining clip (red arrow) in the radiator hose neck.

Lever the retaining clip out until it is in this position (red arrow).
Figure 7

Lever the retaining clip out until it is in this position (red arrow).

Pull the upper radiator hose out of the radiator hose neck.
Figure 8

Pull the upper radiator hose out of the radiator hose neck.

Lift the upper radiator hose out of the plastic holder on the oil filter housing.
Figure 9

Lift the upper radiator hose out of the plastic holder on the oil filter housing.

Twist the radiator hose first to break any corrosion loose.
Figure 10

Twist the radiator hose first to break any corrosion loose. Then remove the hose from the engine block.

This picture illustrates the front of the engine compartment on the right side.
Figure 11

This picture illustrates the front of the engine compartment on the right side. Using a flathead screwdriver, lever up on the retaining clip until it is in the correct position like in Step 7.

Pull the lower radiator hose out of the radiator hose neck.
Figure 12

Pull the lower radiator hose out of the radiator hose neck.

This picture illustrates the engine block side of the lower radiator hose.
Figure 13

This picture illustrates the engine block side of the lower radiator hose. Have a drain pan ready underneath where you are working. Using a flathead screwdriver, loosen the hose clamp on the engine side of the lower radiator hose.

Have a drain pan ready underneath where you are working.
Figure 14

Have a drain pan ready underneath where you are working. Twist the lower radiator hose clamp and pull the hose off the water pump neck.

Lift the lower radiator hose out of the engine compartment.
Figure 15

Lift the lower radiator hose out of the engine compartment. Installation is the reverse of the removal steps. Fit the lower radiator hose into the radiator until it is fully seated and push in the retaining clip. Install the lower radiator hose clamp on the new hose, fit the hose onto the water pump neck and tighten the hose clamp. Fit the upper radiator hose into the radiator, push in the retaining clip and fit the upper radiator hose into the plastic holder on the oil filter housing. Install the hose clamp on the radiator hose, fit the hose onto the thermostat housing neck and tighten the hose clamp. Push the bleed line hose into the upper radiator hose and push up on the spring clip to lock it in place. Fill the cooling system according to our tech article on draining, filling and bleeding your cooling system.

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