123/240D Heater Core

[jseries]

Hi all, I'm going to travel to pick up a 77 123/240D and it may(haven't seen it) have a heater core leak. I've heard that the cores are a nightmare to R&R? I'm generally not intimidated by heater cores but rumor has it these are tough. Any advice would be appreciated. Thank you.

You've been told correct, THEY ARE TOUGH!

I will tell you what I did on my 240D some years ago that has put off this repair. This was probably about ten years ago, and it still does not leak after I went through this process. It was a "what do I have to lose?" approach.

I disconnected the heater hoses to the heater core at the firewall. I connected two hoses in their place. These hoses were long enough to reach to a table that I had next to the fender. I connected one hose to the outlet of a pump. The inlet hose to the pump I put in a pot to suck the contents of the pot. The other hose from the heater core was also placed in the pot to return the solution. The pot was sitting over a can of sterno. I dissolved a can of "Bars Leaks" in about a gallon and a half of water and let it heat. I then turned on the pump and begin to circulate this concoction through the heater core while it was heating. I circulated it for about fifteen minutes during which time the concoction came to a boil several times at which time I would pull out the sterno for a minute or so to cool it below a boiling point for a little bit.

I then removed all this contraption and reconnected the heater hoses. While I was circulating the concoction, I had removed the radiator and block cooling system plugs and let everything drain. After the hoses were reconnected, I began filling the cooling system with 50% antifreeze.

I have drained and refilled the cooling system several times since then and the heater core remains leak free. In the course of this process a tube or two of the heater core may have been plugged up, but the heater still makes plenty of heat. It makes enough that I doubt that I would not have enough heat even if I were in Alaska.

It worked for me, I hope it may be of assistance to you.

Good luck,

[jseries]

Thank you Larry for the reply and the tip!

Larry--

What kind of pump did you use that could handle boiling liquid being run through it?

mike

I forgot to ask--

Would a person have to romove the entire dash to take out the old core?

mike

I used an auxilliary water pump from a 300D. Connected it to the battery with jumpers. It worked great.

Have a great day,

[Ridge]

Boat trash,

To answer your first question about how to remove the heater core, you have to remove the entire dash and then you can get to the heater core. very often the cores are the aluminum ones with the crimped-on tanks and all one needs to do to seal the leak which is often along the seal is to take the unit to your local radiator shop and have the seal crimp recrimped. Then have the shop pressure test the core and if everything is ok, reinstall. At that point, you should be good for a lot more years use.

Obviously, the job will take the better part of a day.
Ben