nlinesk8s

I found a lot of threads regarding replacing the evaporator core, but nothing on the heater core. I guess it's a rare failure (lucky me). Looking at WIS, it doesn't look like the dash has to come out, though the center console, instrument cluster, and the lower panel on the left side does.

The smell is pretty bad with the heater going, so I think I'm going to have to tackle this project. For those who have done this, any advice?

One thing I am going to do is have the AC checked . If the evap has to come out too, I doubt I want to do this twice.

nlinesk8s

Wow. No one has done this? My car is unique?

I have the WIS, so my only real question is whether the steering wheel really needs to come off. I watched a video of an evaporator core removal, and they just dropped the wheel down on the floor.

slammer111

The steering column needs to be dropped, as the cross brace needs to be removed. It requires the removal of the cross brace and upper dash. I imagine the box can then be wiggled out.

The heater core and evaporator core are both inside that heater box, so the steps should be identical.

Donald McPherso

A lot a lot of work.

nlinesk8s

I just got done with replacing the heater core, so I'll make some notes while things are still fresh in my mind:

First off, you do NOT need to remove the entire dash, or crossmembers. That's for the evaporator (a/c) core. You do however, have to take out the lower dash under the steering wheel, and that involves:
steering wheel and multifunction switch removal
center console removal
center stack radio, vents, etc removal
dropping the steering column
loosening one of the "shock absorber" pieces nearest the core.

There are multiple steps inside each of those major steps, and this is one job, unless you're already experienced, or have a lot of time, to use the WIS. Even then you'll be scratching your head from time to time. This job is long and requires a lot of patience. Relax and take your time. Also, if you have a bad back, this is not the job for you, as you'll be doing the "dashboard limbo" a lot.

You will need some special tools, aside from the normal torx set that uses bits and a magnetic handle:
1) Dent Fix or similar antizap tool. IMHO, if you work on a Mercedes without one of these connected, you're taking a big risk.
2) EIS ring removal tool. Amazon or Ebay
3) 10mm hex for the steering wheel, and an extension. And a torque wrench for reinstall.
4) Nice piece of like 1.5" plastic tubing to hold said wheel against rotating, during removal and reinstall. I used an axe handle.
5) Set of fold out torx. You'll need the t30 to remove the airbag, and socket is too short,and a torx with handle is too long. I think you also need this to reach the screw holding the multifunction switch to the column too.
6) T40 (IIRC) hex socket, to unlock the half turn that holds the center console to the dash
7) plastic panel tools ($12 at Autozone) You'll use these frequently elsewhere, so I recommend a set
8) Mirror on a stick. The retaining clips for the tubes to the heater core like to not engage correctly, and you need to be able to see around the back side
9) A good strong headlight, as you're going to be upside down with your head under the dash a lot.

Parts:
heater core (obviously)
inlet/outlet tube o-rings (buy spares, as it's easy to pinch the o-ring during retainer ring install)
antifreeze (obviously)

This job is very doable, but it's multi step, you need to bag and label parts, and you need a lot of patience. Not a good job, if you're not experienced, when you need the car on Monday for work.
Be careful, as you're torquing a lot of small screws into plastic, and they will strip.

Two things I would do different:

1) Refill the system as soon as you've installed the heater core, but before you put anything else back together. If you've missed the o-ring seating correctly, you'll find it then, rather than after the car is reassembled.

2) I'm not sure the steering lock needs to be removed as per the WIS, or the whole multifunction stack disassembled. I don't know why the WIS says this. To remove the steering lock you have to reconnect the battery, and to reinstall it, reconnect the battery. The WIS doesn't mention this, but it's true.

There ya go.

slammer111

Thanks for posting this. Makes the job look quite doable actually. Good to hear that the heater core is way more accessible than the evaporator.

Just wondering, which part turned out to be was leaking? Got any photos?

Occasionally I smell coolant when I start the car, which then goes away after a few seconds. The leakage seems to be minimal. Might be losing a few drops a day. I don't think I'm even losing 0.5mm of coolant a month based on the expansion tank level. Wondering if I should be looking more at the O rings.

Lastly, can you please post a copy of the WIS? Pretty sure some fellow members can benefit from this.

nlinesk8s

Here's the whole story on this: I also smell anti freeze at startup, but not so much after it runs. Also, I never lost enough coolant to notice. So same situation. But after I tore all this out (and damaged the clock spring because the WIS just says "pry it out" and like an idiot I didn't watch a video on removing it) I found an absolutely clean heater core and heater core box. No sign of leaks at all. No sign of leaks from the tubes coming into the footwell.

I have to think I should have bought one of those usb cameras with a long cord, and shoved it down the duct behind the battery to see if there was anything going on there. Also, it's worth checking under the hood for anti freeze smell before starting the car, as for some reason the system sucks air from under the hood.
At this point the cause of the smell in my car remains a mystery.

I've also soured on the WIS. It tells you to disassemble the clock spring and switches, when you didn't need to touch them. It tells you to disassemble the column lock, which you probably don't need to do, and when you get it all back together with a new clockspring, you still can't clear the SRS errors (I have an MBII).
Bottom-line, unless this is gassing you out of the car in the winter and fogging up the windows, let it lie. The trouble isn't worth the gain.

Rather than the WIS, you can find videos on about all the steps, which come down to
0) put the car on ramps, and drain the coolant
1) disconnect the battery ground
2) remove center console
3) remove center stack and vents
4) remove instrument cluster (good time to replace that dim lcd display)
5) remove steering wheel and clock spring assembly (use a taped-in bolt in the proper hole to avoid the clockspring turning before removing it.)
6) remove bottom panel in drivers footwell
7) peel back carpet and remove the duct to the back seat
8) remove the bottom section of dash under steering wheel
9) undo three bolts holding steering column and move down and to the side
10) loosen the crash shock absorber piece nearest the center (it's difficult to reach the bolt head)
11) loosen clamps on heater core tubes and pull out (a square drywall mud tray from Home Depot is good for catching the anti freeze that comes out)
12) remove the clamp on the heater core and remove the heater core.

Good luck!