Heater Core W126 85 300sd - PeachParts Mercedes-Benz Forum

jfarmer64 · #1 11-09-2010, 07:25 PM

Need some help as I know I am close but can't seem to get there from here....

I am replacing the heater core in an 85 300sd. I have the dash out and the heater core is exposed and cannot seem to get the core free. Has anyone done this that can provide some guidance? There is a flap in the way but if I push down I can see down into the well.

The manual I have is close to this car but not quite the same. The heat control is automatic climate control and the pictures in the manual indicate manual controls. Nevertheless, the attached image (I apologize for the quality) from the manual says to remove retainer (50) and lift heat exchanger out. item 50 appears as a bar with 2 screws on the left and the right but do not see this on my auto.

Many thanks for the help!

jfarmer64 · #2 11-13-2010, 07:10 PM

So, the saga continues....

I have taken out the dash and other various pieces of equipment and can see the heater core. Covered in Rust colored dust from the water leak is a strong indication it needs to be replaced. As I go to remove it however there appears to be a bar controlling the flaps obstructing removal. Here are my questions that I hope someone can answer.

Has anyone done this before that can tell me if I need to remove the heater box?

Do I need to drain the AC and open the system.

Do I need to remove the steering wheel?

Diagrams I have indicate that there is a retaining bracket (I think it is hidden in front of the dash and behind the firewall) that has screws that need to be removed. How would I gain access.

Seems like a lot but I have to admit this is frustrating as I can see, touch it but can't seem to figure out how much of the car to disassemble to get to the thing.

Thanks.

PS: It is a plumbers nightmare, the more you work on the drain, the more stopped up it becomes!

kerry · #3 11-13-2010, 07:51 PM

Sorry, I can't help. It sounds like a royal PIA. But if you post pictures of what you've done it might make a good DIY. Did you try running any radiator sealant thru it before disassembling it?

Stevo · #4 11-13-2010, 10:35 PM

A month ago a friend with a 83 euro 300D came by with a leaking heater core, not a bad leak but it wasn't apt to get better. We mixed up a can of 'radiator stop leak" with hot water and circulated it through the heater core with a small pump for about 10 minutes then flushed the core with fresh water and filled the system with coolant...no more leak, thanks to one of our members, thanks Larry

Might be worth a try, heater cores are a real PIA to replace.

kerry · #5 11-13-2010, 10:43 PM

That's exactly what I was thinking. Good to hear it has been successful.

One question: How precisely did you do it? Put the mixture in a bucket, hook the pump to the inlet and feed the outlet back into the bucket?

Junkman · #6 11-14-2010, 08:38 AM

Replace the core if you're going to keep the car. Plan on pulling the dash. It isn't a big deal, only time consuming. Youtube has videos of console & radio removal. There are threads here of dash removal. Steering wheel is easy (10mm Allen Wrench on 3/8 socket). Do the vac pods while you're there. FSM has details on getting to the core. Drain & flush the system - why not? you'll be right there. Take pics. Put everything back clean & tight. You'll have a nice functioning climate control that you won't have to mess with.

Save the suspension for summer.

Stevo · #7 11-14-2010, 07:28 PM

Quote:

Originally Posted by kerry

That's exactly what I was thinking. Good to hear it has been successful.

One question: How precisely did you do it? Put the mixture in a bucket, hook the pump to the inlet and feed the outlet back into the bucket?

sorry for the delay, had a computer malfunction

I disconnected the heater hoses and used a small 12v submersible pump to circulate the HOT "stop leak" and water through the core only.. Pump the mixture through and back to the bucked. Then I swapped ends and pumped it through the other way for another five or ten minutes then pumped hot distilled water through to flush the core. I believe Larry B has been running for a couple years with this "fix" still holding. Ive been wanting too try this ever since i read Larry's post

jfarmer64 · #8 11-17-2010, 06:23 PM

I was supposed to be getting email notifications and post. I just checked back and viola! Many replies. Thanks, I thought no one was interested....

Well, it is out.

After contacting whunter, and rleo, they both set me on the straight and narrow. I was close but had to remove 4 more bolts give a good tug and the heater unit came straight back, giving me access to a forbidden area that had screws. I call this bracket 49 after the diagram in the MB shop manual.

Someone had mentioned this sounds like a real PIA. Understatement. I heard horror stories about the dash. Really that was not as bad as I thought. The heater box however has been areal nightmare. The break through moment was when I lowered the steering wheel. Made things much easier.

Now, If I had it to do over again, here is what I would do differently.

1.) Harbor Freight has a 12 volt dash mounted heater. cost $13.00 Given this is North Carolina and I do not venture often to where it is cold, this would have been a good intermediate plan as I really wanted to go to Pull it yourself Junk place and work on removing one there for practice.

2.) Radiator stop leak through a hand pump. Brilliant idea, Had asked if anyone had waterglassed this and did not get a bite (some forums are not like this forum where people actually respond)

I am quite sure I will be back with a new update and or questions. While I did try to keep everything labeled, I am sure I will have a few "what does this do moments".

Cheers!
J-