W109 heater core removal

[alabbasi]

I have to do this job as mine is leaking pretty badly. How ugly is it?

[berfinroy]

just looked at my Mercedes "Service Manual" covering 1966-1973, and while the last section #83 is labeled "Heating, Ventilation and Air-Conditioning", it's ALL about Air Conditioning! Not a word about Heating or Ventilation. Curious.

[rumb]

Not too bad. It's under the glove box. Be careful removing the valves. You can thread the threaded end of a spark plug where the lever screw is to assist in wiggling the valve out.
Check the cables that go to the levers while there. I cant remember if you remove the glove box you can see in there better.
A good radiator shop should be able to repair.

*the heater fan is the BI!! that's a 20 hr job!

[alabbasi]

Originally Posted by rumb

Not too bad. It's under the glove box. Be careful removing the valves. You can thread the threaded end of a spark plug where the lever screw is to assist in wiggling the valve out.
Check the cables that go to the levers while there. I cant remember if you remove the glove box you can see in there better.
A good radiator shop should be able to repair.

*the heater fan is the BI!! that's a 20 hr job!

Thank you, i heard that the fan was a pita, i thought that the core would be the same.

[TZ_280SEL]

Actually, the AC evap is under the glove box. The heater core is under the center of the dash. You can service the heater core in place but if you are removing it, it’s a good two days in and out. Yes, it is a PITA

[alabbasi]

Yeah it's leaking pretty bad. I'm assuming it needs to come out.

[rumb]

my bad, did it a long time ago....

here are some good instructions

[Idle]

I did a removal in about three hours. It seems like I had to remove everything from under the dash.

Disconnection of everything was just a time consuming chore. The tricky part is removing the unit since the clearance is measured in mm. And not a lot of mms.

I have heard it said that the way the car was produced was the heater box was built first and the car was assembled around it. After doing it you will likely see where this saying is coming from.

But all in all, for you.... This will not be that big of a deal. Just go slow and take it easy. And don't get frustrated.

It's like eating an elephant. You just take one bite at a time.

[twinockchef]

This is the procedure to remove the heater core. If you you do remove the heater box then take the heater core to a radiator shop and have them preform a leak test. Make sure it is prefect. Better safe than sorry.


I just did this last week. It only took me five hours. You will need to take your time with the process of removal and installation. Many of the parts may break. First order a new heater blower fan(replace it now instead of later) and rubber seals for the heater core valves.
1. remove the vent on the dash - two screws
2. remove the left and right covers, which cover the frame between the windshield and door - just pull them out
3. remove the wood dash bow - two screws in the middle under the vent on the dash (be careful not to break it.
4. remove the dash cap - four screws which are close to the defroster vents and then pull the cap off ( it is attached at the front with clips.
5. remove the main a/c vent - unplug the electrical connection on the right side. There are about six screw on the underside it. It should pull right off from the clips which attach it to the dash.
6. remove the a/c blower - two screws on each side
7. remove the evaporator - three bolts, one on the left side against the firewall. The other two are on the inside of the compartment behind the right wheel were the antenna is. Unscrew the a/c lines under the hood. it takes a lot of effort too get it out.
*The lower heater vents will need to come out. To get to them the center carpet has to come out.
8. Remove the center consul - three screws, two in the middle and one at the front also disconnect the window switches.
9.remove the center carpet and the carpet on the left and right side.
10. unscrew the vents which are of the floor - two screws each.
11. remove the vents which connect to the bottom of the heater box - one screw each.
12. remove the glove box door.
13. remove the glove box interior - two screws and about seven clips. Unclip the light and then pull out the interior box.
14. remove the ash tray front
15. unscrew the four screws which hold the ash tray holder. One of which is the switch four the glove box light.
16. remove the radio
17. pull out the instrument cluster - there is a plastic nut which holds the cluster in. To get to it you will need to reach up from under the dash (this is easier said than done). With the nut off carefully pull the cluster out. Disconnect the speedometer cable, oil pressure line, electrical plug and the shifter indicator (this disconnects close to the steering column under the dash. Move the shifter and you should see the linkage move back and forth). the temperature cable cannot be disconnected. I just rotated the cluster and taped it to the left side of the dash. *be careful not to scratch the wood on the dash with the back of the cluster.*
18. remove the heater controls (this is a pain in the ass). There are two 10mm nuts on each side which hold the heater control face plate on. Unclip each cable connection (label them), two of which require a screw drive from the top (through the controls) and the bottom. Don't lose the clips. They like to pop out and vanish into the black hole of the dash. There are also two electrical plugs on each side of the controls.
19. remove the a/c hose - this hose runs from the far left vent down to the left side of the main a/c vent. It is the hose which right behind the instrument cluster. Be careful it likes to break.
20. remove the three defroster vents - the left and right ones are secured with clips which are on top of the dash. Unscrew from the dash and then remove clips from the vent. The right vent will fall out but the left vent will just moved to the side (watch for the small hose at the left of it.). The center vent is removed by a single screw at the center of the dash under the dash vent.
21. drain the cooling fluid from the radiator.
22. disconnect the heater core hose connections - inside of the engine compartment on each side of engine.
23. unscrew the heater box - two 10mm nuts on each of the box at the fire wall.
24. disconnect the electrical plug from the heater box - it is right next to the valves on the right side.
25. there is a bolt which attaches the box to the dash - it is on top at the front of the box. There may also be a connection at the lower front of the box.
Now you can remove the heater box. First pull the box back to get the heater core pipes out of the holes in the firewall. Then slide the box to the right. It takes a lot of finesse. Rotating the right side up while at the same time pushing to the right (this will help in getting the heater blower fan to clear the top of the dash. Go slow and be patient. It will come out.
This list may appear overwhelming but it works. The order od operations works well too.
If I missed something let me know.
Good Luck
Twinoakchef

[rumb]

You can make a bit more room to get the box out by using a big rubber hammer to pound down the right side of the trans tunnel about 1/2".

I figure that the heater box was the first thing put into the chassis from the left side. but you would have to remove the entire steering column to get it out that way now.

[alabbasi]

Thank you all, and yes this is the era when Mercedes Benz started their production line by hanging a heater off a string and building the rest of the car around it. It's still better than working on any British luxury car.

[Idle]

Originally Posted by alabbasi

Thank you all, and yes this is the era when Mercedes Benz started their production line by hanging a heater off a string and building the rest of the car around it. It's still better than working on any British luxury car.

Yup. And that goes all the way back to those monsters from the late 50s. If you like working in tight and inaccessible places then you will love owning a Jag.