Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Heater Core Hoses Replacement
 
Bookmark and Share

Pelican Technical Article:

Heater Core Hoses Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$30 to $100

Talent:

***

Tools:

16mm, 13mm, 10mm socket, E12socket, puller, hose clamp remover, long handled needle nose pliers, trim removal tool

Applicable Models:

Mercedes-Benz C250 (2012-14)
Mercedes-Benz C300 (2008-14)
Mercedes-Benz C350 (2008-14)

Parts Required:

Hoses

Hot Tip:

Watch the hood when working on the arms

Performance Gain:

Working heat

Complementary Modification:

Coolant flush

There are two hoses connected to the heater core where it exits the firewall and between the bulkhead. The supply hose comes off of the rear of the head. This hose supplies the coolant that gets hot the fastest in the motor, which in turn allows you to run the defroster and get moving quicker. The other hose returns the hot coolant back into the system. These hoses are not known to fail often, which is a good thing because they are a pain to get to and change. If you have checked every hose and the connections and are still losing coolant you will need to check and perhaps replace these hoses.

The hoses are at one of the high points in the system, so it is possible to change them out with doing a complete coolant drain, but you will still need to fill and bleed the system when you are done. I highly recommend if you have been chasing a leak to give your coolant system a good and complete flush and bleed the system while performing this work. Please see our article on coolant flushing for additional assistance.

No matter which route you take make sure you do this work while the system is cool, and please be prepared to catch and dispose of the coolant correctly.

The two heater core hoses (red arrow, not shown) are located between the firewall and bulkhead, under the windshield wiper motor and cowl or rain diverter, so you need to remove all of these components to access the hoses.
Figure 1

The two heater core hoses (red arrow, not shown) are located between the firewall and bulkhead, under the windshield wiper motor and cowl or rain diverter, so you need to remove all of these components to access the hoses. It is not difficult, just time consuming.

Before you remove the arms take note of the dot hidden in the silk screen area of the lower windshield (adjacent to lower yellow line).
Figure 2

Before you remove the arms take note of the dot hidden in the silk screen area of the lower windshield (adjacent to lower yellow line). The wipers must be aligned within an inch of this dot (yellow lines) when in the off position.

Remove the plastic cover over the driver side arm (red arrow).
Figure 3

Remove the plastic cover over the driver side arm (red arrow). It just snaps off.

Use a trim removal tool and pry the caps off the two arms for the passenger side (red arrows).
Figure 4

Use a trim removal tool and pry the caps off the two arms for the passenger side (red arrows).

Use a 16mm socket.
Figure 5

Use a 16mm socket. While holding the arm in place loosen the nut (red arrow). Be careful working around the windshield and the hood, as you do not want to damage them. Do the same to the two nuts on the passenger side arms.

Sometimes the arms can be wiggled and pulled off the mechanism.
Figure 6

Sometimes the arms can be wiggled and pulled off the mechanism. On our project car we had to use a puller. If you need to use a puller a simple tie rod separator will do. Leave the nut on the last couple of threads (red arrow) to keep the puller in place, and then pop the arm off.

With the arms free you can remove the wiper and arms on both sides.
Figure 7

With the arms free you can remove the wiper and arms on both sides. Again use caution so as to not damage the windshield or hood.

There are four plastic push/pull clips on the cowl or rain diverter (red arrows).
Figure 8

There are four plastic push/pull clips on the cowl or rain diverter (red arrows).

Use a trim removal tool, and carefully pry the pin out from the base.
Figure 9

Use a trim removal tool, and carefully pry the pin out from the base. Then pull the whole clip out.

You can also use a small Philips head screwdriver to unscrew the clips but they are plastic and tend to strip out the heads pretty quick.
Figure 10

You can also use a small Philips head screwdriver to unscrew the clips but they are plastic and tend to strip out the heads pretty quick.

The cowl or rain diverter clips into a metal channel (red arrow) on the bottom of the windshield.
Figure 11

The cowl or rain diverter clips into a metal channel (red arrow) on the bottom of the windshield. Start at one side and carefully lift the plastic cowl up and out from the windshield (yellow arrow).

Flip the cowl over and pull the nearest washer nozzle out.
Figure 12

Flip the cowl over and pull the nearest washer nozzle out. Separate the fluid hose from the washer fluid tank by pulling it back and off (red arrow).

There is a brace (yellow arrow) from the top of the left wheel well that mounts on two studs under the windshield (green arrows).
Figure 13

There is a brace (yellow arrow) from the top of the left wheel well that mounts on two studs under the windshield (green arrows). Use an E12 and remove the single bolt (red arrow). This will allow you to lift the brace up. From there it simply pulls straight off the studs under the windshield.

Disconnect the electrical connection from the wiper motor by squeezing in the tab and pulling it off (red arrow).
Figure 14

Disconnect the electrical connection from the wiper motor by squeezing in the tab and pulling it off (red arrow).

Use a 13mm socket, and remove the two nuts on the base of each arm (red arrow).
Figure 15

Use a 13mm socket, and remove the two nuts on the base of each arm (red arrow).

Use a 13mm socket, and remove the long bolt that sits in the rubber isolator by the motor (red arrow).
Figure 16

Use a 13mm socket, and remove the long bolt that sits in the rubber isolator by the motor (red arrow).

You can now lift the unit out.
Figure 17

You can now lift the unit out. Again use care so as to not damage the windshield or hood.

With the wiper motor removed you can see and access the upper supply hose (red arrow).
Figure 18

With the wiper motor removed you can see and access the upper supply hose (red arrow). Unfortunately, the return hose clamp is hidden (yellow arrow). You need to remove the right side molding to get at it.

Use a set of long needle nose pliers, and turn the wiper arm mount counter clockwise to remove it (red arrow).
Figure 19

Use a set of long needle nose pliers, and turn the wiper arm mount counter clockwise to remove it (red arrow).

Next, use a 10mm socket.
Figure 20

Next, use a 10mm socket. Remove the four nuts holding the plastic molding in place (red arrows).

Unclip the molding from the rain diverter on the right side by the A-pillar, and lift it out of the engine bay.
Figure 21

Unclip the molding from the rain diverter on the right side by the A-pillar, and lift it out of the engine bay. This will now give you access to the return hose clamp.

You are going to be working in a tight space, and if the hoses have not been replaced before they will have the factory clamps on them.
Figure 22

You are going to be working in a tight space, and if the hoses have not been replaced before they will have the factory clamps on them. While you can compress these clamps with channel locks or vice grips, if you have ever thought about investing in a good set of hose clamp removal tools, now would be a good time. Both the upper supply hose and lower return hose can be removed from the heater core by compressing them and sliding the hose off (red arrows).

When you remove the hoses even if you have drained the system, be prepared for some additional coolant to escape from the core (yellow arrows) and hoses.
Figure 23

When you remove the hoses even if you have drained the system, be prepared for some additional coolant to escape from the core (yellow arrows) and hoses. Be prepared to catch it and dispose of it correctly. The hose out from the head is a factory clamp as well (red arrow). You just compress it and slide it off.

The return hose to metal pipe clamp (red arrow) is a tight fit.
Figure 24

The return hose to metal pipe clamp (red arrow) is a tight fit. Compress the clamp, slide the hose off and replace it. Installation is the reverse of removal. Do not forget to refill or top up and bleed the system.

Bookmark and Share
Comments and Suggestions:
Kate Comments: I bypassed the heater core on a 1997 E300D, but coolant is still leaking into the passenger compartment. Why is that? And is it ok to bypass the heater core and still run the car? Thanks for your help.
November 18, 2016
  Followup from the Pelican Staff: Probably left over coolant in the heater core. - Nick at Pelican Parts  

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Fri 12/2/2016 02:54:32 AM