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Pelican Technical Article:

Coolant Hose Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$60 to $200

Talent:

**

Tools:

Flathead screwdriver, pliers, floor jack, jack stands, wheel chocks, safety glasses

Applicable Models:

Mercedes-Benz C350 (2008-15)
Mercedes-Benz GLK350 (2010-15)

Parts Required:

New hoses

Hot Tip:

Work on a cool car

Performance Gain:

Proper operating temperature

Complementary Modification:

Flush the radiator

There are not a lot of radiator hoses on the Mercedes-Benz W204. In addition, there's a fair amount of room to work on them, which makes inspecting and replacing them an easy DIY job. I recommend inspecting your rubber hoses every two years or so. As they age, they have a tendency to get hard and brittle. When you gently squeeze a hose, it should be relatively soft and easy to indent with your hand. It shouldn't feel like it is brittle or crunching when you squeeze it. It should spring back to its original shape pretty quickly after being compressed. If it feels very hard, then it might be time to replace it. If there is a bulge in the hose, or any type of crack in the surface of the hose, then you should replace it as well. Also check for leaks around where the hoses create their connections--that is a sign that the hose should be replaced.

To replace the hoses you will need to remove the engine covers as well as drain the coolant. Please see our article on engine cover removal and radiator flush and drain for additional assistance.

You need to remove the front engine cover (red arrow) and the air ducts (yellow arrows) to replace the coolant hoses so please see our article on engine cover removal for additional assistance.
Figure 1

You need to remove the front engine cover (red arrow) and the air ducts (yellow arrows) to replace the coolant hoses so please see our article on engine cover removal for additional assistance.

Next, you need to remove the under body trays and drain the radiator (red arrow).
Figure 2

Next, you need to remove the under body trays and drain the radiator (red arrow). Please see our article on these procedures for further assistance.

There are three coolant lines: the left side line that connects the radiator to the thermostat and reservoir (red arrows), the right side hose that connects the radiator to the water pump and heater core (yellow arrows) and the hose that connects the coolant reservoir to the radiator (green arrow).
Figure 3

There are three coolant lines: the left side line that connects the radiator to the thermostat and reservoir (red arrows), the right side hose that connects the radiator to the water pump and heater core (yellow arrows) and the hose that connects the coolant reservoir to the radiator (green arrow).

To replace the thermostat line begin by removing the hose from the clips along the front of the shroud where it runs to the overflow reservoir (red arrow) and release the clip where it mounts to the oil cooler (yellow arrow).
Figure 4

To replace the thermostat line begin by removing the hose from the clips along the front of the shroud where it runs to the overflow reservoir (red arrow) and release the clip where it mounts to the oil cooler (yellow arrow).

Use a flathead screwdriver and release the quick release clip from the thermostat (red arrow).
Figure 5

Use a flathead screwdriver and release the quick release clip from the thermostat (red arrow).

Wiggle and pull the hose from the thermostat and be prepared for some coolant to spill out.
Figure 6

Wiggle and pull the hose from the thermostat and be prepared for some coolant to spill out.

Release the hose from the coolant reservoir by using a small flathead screwdriver to lift up the quick release and pull the end of the hose out from the reservoir (red arrow).
Figure 7

Release the hose from the coolant reservoir by using a small flathead screwdriver to lift up the quick release and pull the end of the hose out from the reservoir (red arrow).

Use a flathead screwdriver and release the quick release clip from the connection to the radiator and wiggle and pull the hose out (red arrow).
Figure 8

Use a flathead screwdriver and release the quick release clip from the connection to the radiator and wiggle and pull the hose out (red arrow).

This photo illustrates the hose out of the vehicle.
Figure 9

This photo illustrates the hose out of the vehicle. Installation is the reverse of removal.

Remove the right side hose by using a flathead screwdriver and releasing the quick release clip and pulling the hose out from the water pump (red arrow).
Figure 10

Remove the right side hose by using a flathead screwdriver and releasing the quick release clip and pulling the hose out from the water pump (red arrow). Even though you have drained the radiator, be prepared for some coolant to spill out.

Using a flathead screwdriver release the quick release clip and pull the upper section of the hose from the radiator (red arrow).
Figure 11

Using a flathead screwdriver release the quick release clip and pull the upper section of the hose from the radiator (red arrow).

There is a fitting that connects this hose to the heater core (red arrow).
Figure 12

There is a fitting that connects this hose to the heater core (red arrow). Use a set of pliers and compress the clamp and separate the hose connection.

This photo illustrates the hose removed from the vehicle.
Figure 13

This photo illustrates the hose removed from the vehicle. Installation is the reverse of removal.

You can remove the reservoir supply hose by using pliers to remove it from the bottom of the reservoir and a flathead screwdriver to remove it from the quick release connection on the radiator (red arrow).
Figure 14

You can remove the reservoir supply hose by using pliers to remove it from the bottom of the reservoir and a flathead screwdriver to remove it from the quick release connection on the radiator (red arrow). Installation is the reverse of removal. Do not forget to fill and bleed your coolant.


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