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Radiator Hose Replacement on Your Mercedes
 
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Pelican Technical Article:

Radiator Hose Replacement on Your Mercedes

Steve Vernon

Time:

2 hours2 hrs

Tab:

$100

Talent:

**

Tools:

Flat head screw driver, pliers,

Applicable Models:

Mercedes-Benz C320 (2001-04)
Mercedes-Benz CLK320 (1998-04)
Mercedes-Benz E320 (1998-04)
Mercedes-Benz ML320 (1998-03)
Mercedes-Benz S320 (1998-99)
Mercedes-Benz SLK320 (2001-03)

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 W203 and 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 two air inlet ducts and the front engine cover.

Remove each duct by compressing them towards the engine and slipping them off the air inlet.

With the ducts off, remove the front engine cover. It pulls up and away from the engine. The cover is held on by five clips and will easily come off with hand pressure.

Next, safely jack up and support your car. With the car safely off the ground, you will need to remove the engine tray. There are six 8mm bolts holding the tray on, the rear two also help hold the transmission tray. If you are going to leave the transmission tray on, remove the rear two bolts first, lower the engine tray, reattach the transmission tray bolts, then remove the remaining four bolts on the engine tray.

With the tray removed you will see radiator drain plug on the lower left front of the car. Place a catch bucket or tray under the plug and use a large flat head screw driver to open the drain plug.

The fluid will come out slowly at first so open the tank cap to break the vacuum and help speed things up. The fluid drains out a small spigot facing rearward and not through the red plug.

Remove the upper radiator to coolant pump hose. Mercedes-Benz uses quick disconnect attaching points where the hose meets the radiator, but sometimes the wire clip you need to pull out is facing something that does not allow it to be pulled straight out. If this is the case just unclip it from the radiator and then pull the hose out. You will need to reinstall it before reattaching the hose.

The other end of the hose is attached to the thermostat by a traditional hose clamp. Use a flat head screw driver, loosen the clamp and remove the hose. In the middle of this hose there is a smaller overflow hose that attaches and branches off to the reservoir. Use a flathead screwdriver and remove the clamp and hose from the reservoir.

Underneath the overflow hose is the auxiliary coolant pump. There is a hose that runs from the auxiliary coolant pump to the coolant pump on the engine, use a set of pliers and disconnect this hose from the auxiliary pump.

On the lower right part of the radiator remove the quick disconnect coolant hose, this hose is lower than the radiator drain plug so fluid will come out of it when you remove it, be prepared to catch and dispose of the fluid properly. This is also a quick disconnect fitting that is at an odd angle, I just unclipped it and separated the hose from the radiator. Remember to reinstall it before install the new hose.

There are two hoses that connect to the lower part of the coolant pump on the engine: one from the auxiliary coolant pump and one from the lower right radiator. Both are held on by traditional hose clamps, use a flat head screw driver and remove both clamps and hoses. You may have to run a small screw driver between the hose and pump to break the seal or if you are replacing them any way just cut them off.

Installation is the reverse of removal. Make sure you reset the quick disconnect clips before refilling the system with coolant.

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.
Figure 1

You will need to remove the two air inlet ducts (red arrows) as well as the front engine cover (yellow arrow) to get access to the air filter housing on top of the engine.

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.
Figure 2

Remove each duct by compressing them towards the engine (red arrow) and slipping them off the air inlet.

With the ducts off remove the front engine cover.
Figure 3

With the ducts off remove the front engine cover. It pulls up and away from the engine (yellow arrow).

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.
Figure 4

The cover is held on by five clips (red arrows) and will easily come off with hand pressure.

With the car safely supported off the ground you will need to remove the engine tray.
Figure 5

With the car safely supported off the ground you will need to remove the engine tray. There are six 8mm bolts (red arrows) holding the tray on, the rear two also help hold the transmission tray. If you are going to leave the trans mission tray on, remove the rear two bolts first, lower the engine tray, reattach the transmission tray bolts, then remove the remaining four bolts on the engine tray.

With the tray removed you will see radiator drain plug on the lower left front of the car.
Figure 6

With the tray removed you will see radiator drain plug on the lower left front of the car. Place a catch bucket or tray under the plug and use a large flat head screw driver to open the drain plug (yellow arrow).

The fluid will come out slowly at first so open the tank cap to break the vacuum and help speed things up.
Figure 7

The fluid will come out slowly at first so open the tank cap to break the vacuum and help speed things up. The fluid drains out a small spigot (yellow arrow) facing rearward and not through the red plug.

Remove the upper radiator to coolant pump hose.
Figure 8

Remove the upper radiator to coolant pump hose. Mercedes-Benz uses quick disconnect attaching points, but sometimes the wire clip (red arrow) you need to pull out is facing something that does not allow it to be pulled straight out. If this is the case just unclip it from the radiator and then pull the hose out. You must reinstall it before reattaching the hose.

The other end of the hose is attached to the thermostat by a traditional hose clamp (red arrow).
Figure 9

The other end of the hose is attached to the thermostat by a traditional hose clamp (red arrow). Use a flat head screw driver, loosen the clamp and remove the hose. In the middle of this hose there is a smaller overflow hose (yellow arrow) that attaches and branches off to the reservoir.

Use a flathead screwdriver and remove the clamp and hose from the reservoir (yellow arrow).
Figure 10

Use a flathead screwdriver and remove the clamp and hose from the reservoir (yellow arrow). Underneath the overflow hose is the auxiliary coolant pump. There is a hose that runs from the auxiliary coolant pump to the coolant pump on the engine (red arrow).

Use a set of pliers and disconnect this hose from the auxiliary pump.
Figure 11

Use a set of pliers and disconnect this hose from the auxiliary pump.

On the lower right part of the radiator remove the quick disconnect coolant hose (red arrow), this hose is lower than the radiator drain plug so fluid will come out of it when you remove it, be prepared to catch and dispose of the fluid properly.
Figure 12

On the lower right part of the radiator remove the quick disconnect coolant hose (red arrow), this hose is lower than the radiator drain plug so fluid will come out of it when you remove it, be prepared to catch and dispose of the fluid properly. This is also a quick disconnect fitting that is at an odd angle, I just unclipped it and separated the hose from the radiator. Remember to reinstall it before install the new hose.

There are two hoses that connect to the lower part of the coolant pump on the engine: one from the auxiliary coolant pump (red arrow) and one from the lower right radiator (yellow arrow).
Figure 13

There are two hoses that connect to the lower part of the coolant pump on the engine: one from the auxiliary coolant pump (red arrow) and one from the lower right radiator (yellow arrow). Both are held on by traditional hose clamps, use a flat head screw driver and remove both clamps and hoses. You may have to run a small screw driver between the hose and pump to break the seal or if you are replacing them any way just cut them off.

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Comments and Suggestions:
Rayman Comments: Well done Nick, but my wife's C320 Wagon has a three way hose which I have identified, late chassis number. Will the removal of the engine tray give me clear access to the engine and lower radiator connection? Looks tight.
April 15, 2016
  Followup from the Pelican Staff: Yes, it should. With the splash shield removed, you will have better access. - Nick at Pelican Parts  
Yoreiza Comments: On the figure 13,

Can you give me the proper parts number for the hose pointed by yellow arrow?

Thank You
September 26, 2015
  Followup from the Pelican Staff:
I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need. - Nick at Pelican Parts
 
Bob Comments: Great write up!
November 20, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
TT Comments: Excellent
July 31, 2014
  Followup from the Pelican Staff: Thanks. - Nick at Pelican Parts  

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