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Bad heater core?

34K views 133 replies 14 participants last post by  Clarkz71 
#1 ·
Just replaced Mono valve for hot air issue problem ,but now leaking coolant at drains below heater core location,I can see the drips when I crawl under there,weird how it just started last week leaking while I was testing old MV for voltage and cleaning the inside of it,guess I'm committed to pull the dash now, what fun.:frown I have a feeling this w124 my son bought on eBay is haunted!
 

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#33 ·
WooHoo!!!!! its out! unbelievable how much stuff I had to disconnect! managed not to break anything,total time about 4,5 hrs but I spread it out over 4 days ,now I can test all the vacuum pods,split the case and start making a parts list, so........ if you find a really good deal on a spotless,perfect running W124 but the AD says a/c or heater not working,take a long look at this!
 

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#34 ·
great the easy part is done. now put it back together with every thing working thats the fun:grin

one tip test every thing as you put it back together you dont want to put dash back in and find out the flap wont work:smile
 
#36 · (Edited)
I think the heater core p/n# might be A0028356401, but verify with your local dealer by running your vin# to ensure a good match.

The part# above is what my local MB dealer sent me, but mine is a E250 with the semi-automatic dual temp wheel style HVAC controls that uses a duo valve vs the monovalve setup used in the full automatic HVAC controls.

But there is a chance the heater core is shared between the 2 systems.
 
#39 ·
While researching this issue ,I found tons of posts on w124 evaporator replacements but hardly any for heater core replacements? must not be a common issue on Mercedes???
This is funny,in the drivers ventilation duct located at floor board,I found 8 pencils,2 tubes of crazy glue.5 tootsie roll mini's,and part of a broken glass jar??? how did that get there? PO was a fat ass chick.:eek
 
#41 ·
The magic box is apart! tons of fasteners,looking at heater core looks fairly clean,but the bottom of it is made out of some sort of plastic,thought it would have signs of coolant residue there but don't see any? maybe the leak is higher up on core and just sprayed the evaporator eventually finding its way down to the drains. I took lots of pictures so I can remember how this beast came apart.
next will test all pods for the heck of it!
 

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#44 ·
Your welcome! figure it will help someone one day,lots of info out there,a little more never hurts!
Now I need help!!!!!! found all pods for replacement at Autohauz except the center nozzle that's inside the unit,its black,it does test good but need to replace it, its the one behind top red line,anyone have a source????? or part number,can not read yellow sticker on it,only thing I can make out is 91,its #40 on diagram.
thanks!
 

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#45 ·
Your welcome! figure it will help someone one day,lots of info out there,a little more never hurts!
Now I need help!!!!!! found all pods for replacement at Autohauz except the center nozzle that's inside the unit,its black,it does test good but need to replace it, its the one behind top red line,anyone have a source????? or part number,can not read yellow sticker on it,only thing I can make out is 91,its #40 on diagram.
thanks!
...it might be a good time to hit up that local mercedes dealer that put temecula on the map!
 
#46 ·
Yea? I can do that,also just remembered one of my buddies at SD MB,he's the parts manager and can get it at cost,will look into that.

Now here's some pic's of heater core,took the pipes out,they are on there pretty tight so spray some lubricant at the seals and gingerly start moving them,be careful! they are aluminum and can bend easily! there is reminants of oil from blown HG in there.
also I have a r134a retrofit seal kit I bought 2 years ago and never used it,I need a few seals for the evaporator and maybe receiver drier, keeping system R12, OK to use these??? or is there a big difference between R12 and r134a seals? my a/c guy says use them.
 

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#47 ·
You have a R12 factory equipped car. You have spare R12 gas.

What's with this retrofit crap??? Nothing works as good as R12.

Make sure you replace that drier, and I would highly suggest you do all the sensor, washer/seals that attach to the dryer as well.
 
#48 ·
I'm keeping it r12,have a new RD from AH AZ, filling out my parts list,will need a seal kit for a few parts ,just O rings,I'm just wondering if I can use the O rings from the kit in previous picture? are O rings for r12/R134a made differently? different freon .

here's the kit AH AZ sells


Santech
A/C O-Ring Kit; Rapid Seal Kit
1992 Mercedes 300E
 

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#53 ·
the ones today at AH AZ are green,so it should be R12 OK, am I reading this right?

Many of the
air conditioning
o
-
rings are the same size but are manufactured in multiple colors. There are
many different materials used but HNBR will work in all applications. Santech has chosen to supply
Green HNBR for al
l U.S. applications of automotive air conditioning o
-
rings. Santech
HNBR is a high
temperature material and is compatible with R12, R134a, Mineral Oil, PAG Oil, and Ester. Green was
the most widely used color for HNBR and was chosen as the standard
Sant
ech
color. Almost all
aftermarket companies have followed Santech’s lead and have standardized to this system. Santech also
has most of the other colors available for the European market and for special order requirements.
 
#56 ·
No,it was leaking big time via the evaporator drains with a/c off ,enough for low coolant light to come on, coolant tank would empty in 5 minutes of car running, heater hoses(3) entering firewall showed no signs of leakage,go figure? has to be heater core,what else is there in the box? again, not condensate from evap.
 
#57 ·
So I call Fletcher Jones Temecula,no answer,get on their site and shoot them a email for part I need,checked my inbox and get this? what the hell?lol


Thank you for your interest in employment with Fletcher Jones Motorcars. We will review your request with our current employment opportunities and may contact you for additional information. We wish you much success!
 
#59 ·
You want mineral oil, and the specs should be in the FSM.

Since we're on the general topic, does anyone know when/if MB chose a different means of securing the climate box to the body? When I dismantled and parted out an '87 300TD, I had to use what I thought was excessive force to pry out the box, and really couldn't of imagined doing it in a car I wanted to save. If I remember right, it used a combination of glue infused foam and butyl rope as the securing agents. I'm preparing to pull the dash and pull the box on my '90, and desperately hope it comes out much easier.



 
#60 ·
All 124's use that seal Casey. And they all feel stuck because they are.

The trick to removing the case without damage is to sit as close to the middle
of the car as possible on the pass seat, grasp the case by each side in a solid
location (I use the side vent outlets) and work it side to side with a moderate amount of pull.

Some come out easier then others, but you'll feel it start to move.
Just keep up the side to side pulling.


.
 
#62 ·
Ok, I was hoping it was like the difference between early and late 123 front fenders...you know, the early ones with the thick glue that virtually ensures that they don't come off intact, vs the late ones which lift right off. I just remember applying really intense leverage that felt like I was going to bust off the tabs or break free and crack the windshield. Other than freeing the box, it's not that bad of a job.
 
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