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Pelican Technical Article:

Heater Hose Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$100 to $150

Talent:

***

Tools:

Flathead screwdriver, pliers

Applicable Models:

Mercedes-Benz C350 (2008-14)
Mercedes-Benz GLK350 (2010-14)

Parts Required:

Heater hose

Hot Tip:

Work on a cold car

Performance Gain:

Working heat

Complementary Modification:

Flush cooling system

There are two heater hoses hoses on the Mercedes-Benz C350 and both can fail over time. 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.

One hose is located on the front right side of the engine bay, while the other is at the left rear of the engine. Due to the level of the hoses I recommend draining the fluid before you replace the hose. If the coolant is still good drain it into a clean container and reuse it. If the coolant is old now is a good time to give the system a complete flush. Please see our article on draining and flushing your coolant.

You will need to remove the engine covers (red and yellow arrows) and air intake ducts (green arrows) to perform this work.
Figure 1

You will need to remove the engine covers (red and yellow arrows) and air intake ducts (green arrows) to perform this work. Please see our article on engine cover removal for additional assistance.

If you are draining the coolant you will need to remove the under body trays to access the radiator drain plug (red arrow).
Figure 2

If you are draining the coolant you will need to remove the under body trays to access the radiator drain plug (red arrow). Please see our article on coolant drain and flush for additional information.

One hose is located on the front right side of the engine bay, while the other is at the left rear of the engine (red arrows).
Figure 3

One hose is located on the front right side of the engine bay, while the other is at the left rear of the engine (red arrows).

The left hose is located between the MAF and the left cylinder head below the main wiring harness (red arrow, not visible).
Figure 4

The left hose is located between the MAF and the left cylinder head below the main wiring harness (red arrow, not visible). If you have small hands you may be able to replace the hose without removing the MAF but it only takes a minute to remove it and makes the job so much easier.

You next need to remove the MAF (red arrow) and vacuum line (yellow arrow).
Figure 5

You next need to remove the MAF (red arrow) and vacuum line (yellow arrow). Please see our article on MAF sensor replacement for additional information.

Disconnect the breather hose from the rear of the right cylinder head (red arrow).
Figure 6

Disconnect the breather hose from the rear of the right cylinder head (red arrow).

Unclip the two plastic clips on the elbow piece between the MAF and throttle body (red arrow) and remove the elbow and attached hose.
Figure 7

Unclip the two plastic clips on the elbow piece between the MAF and throttle body (red arrow) and remove the elbow and attached hose.

You now have room to remove the hose.
Figure 8

You now have room to remove the hose. Use a flathead screwdriver and pry up the quick release clip on the heater hose (red arrow).

Use care when separating the hose form the valve (red arrow).
Figure 9

Use care when separating the hose form the valve (red arrow). The hose and valves ends are plastic. You do not want to damage it, or you will end up replacing the valve as well.

Use the flathead screwdriver and release the clip on the hose where it meets the firewall (red arrow).
Figure 10

Use the flathead screwdriver and release the clip on the hose where it meets the firewall (red arrow).

Depending on the brand of hose you get you may need to transfer this quick disconnect to the new hose (red arrow).
Figure 11

Depending on the brand of hose you get you may need to transfer this quick disconnect to the new hose (red arrow). This is much easier and safer to do with the hose out of the car.

The heater hose on the front connects the hard line (red arrow) to the rubber line (yellow arrow).
Figure 12

The heater hose on the front connects the hard line (red arrow) to the rubber line (yellow arrow).

The hose is connected to the hose on the bottom of the water pump and can be removed from both the rubber hose and hard line with pliers (red arrow).
Figure 13

The hose is connected to the hose on the bottom of the water pump and can be removed from both the rubber hose and hard line with pliers (red arrow). Installation is the reverse of removal. Do not forget to refill and bleed the coolant.


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