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After 26 years, it is time.

7K views 81 replies 21 participants last post by  281lxm 
#1 ·
Well I got in the C126 and the Texas heat was coming but the airflow inside the car was hot. From perfect the day before to nada! Removed and replaced Klima relay, no change. Hooked up a can and I was EMPTY, no refrigerant. 1 can in and compressor came on, 1/2 can and aux fan kicked in. Cold air back from auto-part store. Few hours later, fire up car and cool but not cold, I backup and breath the band-aid smell of 134a. Stop the car midway down the drive and there it is, worst nightmare! Dinner plate size gob of green fluid smelling like a case of bandaids. Go back and look at transmission and its dripping green condensate. So I either have O ring failure at the evaporator or failure in the core itself, not possible to get refrigerant out the drains, those items are sealed deep in the bowels of the airbox.

Dash removal, and replacement of Orings, expansion valve and new evaporator. While I am in there, replacing vacuum pods that I did not replace in 2012.
 
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#7 ·
Thanks Dan! I didn't state that I used a similar product but the results after 10 mins of refill were the same[emoji25][emoji25][emoji25]

This will be a one and done for all things under the dash, and will review heater core as well.
 
#8 ·
I don't EEVEN wanna think about what you have to look forward to, tearing out the dash to get to what needs to be taken care of but like you said Louis, do it all while you're in there and it's apart
 
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#9 ·
Go back and look at transmission and its dripping green condensate. So I either have O ring failure at the evaporator or failure in the core itself, not possible to get refrigerant out the drains, those items are sealed deep in the bowels of the airbox.
Oh man, what a job you have in store..

I agree with you that the evaporator core is bad now.. As the High & Low side connections to the Evaporator [o-rings] are external to the HVAC box.. that green mess would be all over your right foot and into the carpets were they leaking.. Yuck!

In addition to the previous advice and consolation, I'd recommend getting the HVAC door & linkage kit from MB [#23] in the pic.. 0008301233

https://www.ecstuning.com/b-genuine-mercedes-benz-parts/lever/0008301233/

As you can see, its got a whole bunch of tiny bell cranks & HVAC gizmatrons that I see get brittle over time, snap.. then render some vital little thing inside the box inoperative.... For example, I've read it many times that the drivers side: no heat... = broken linkage to the left 'floor door'. You might consider those flap doors, numbers 35 & 38 on the picture..

An idea anyways.

MBL
 

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#10 ·
I verified availability of such things while running thru the parts list.
 
#11 ·
Eesh, wouldn't wish that job on anyone.

I've been wondering if it seems to be in hot places more, perhaps where the coolant isn't circulating so much through the heater box. Only cos I've not heard of this problem over here.
 
#12 · (Edited)
Hey ian,

He's got green in the condensate drip...

That's the Evaporator fail..

Has to be.

To YOUR point: Many years ago, I'm talkin' Volvo 240 days, the last century now, there were a spate of heater core failures with that model.. LOTS of 'em.... in they south western states here in USA. Especially Arizona.

It turns out, the heater was not needing usage there, sometimes for years....

The heater cores corroded from the inside out, as you allude to... due to the coolant [in the heater matrix/core] losing its anti-corrosion due to non use.

During that time span, nowhere else here [in USA] was this an issue.

MBL
 
#13 ·
I use the ac daily but certainly run the heater when I change any of the fluids. Sadly I cannot tell what has blown until you tear open the box. So at that point there isn't any way in hell I am not replacing all of it, even if it is a 25 cent O ring. Seems more plausible that the O ring blew rather than the core, but the fix requires same ugly prep. I will snap pics as I get to the box.
 
#14 · (Edited)
Sadly I cannot tell what has blown until you tear open the box. So at that point there isn't any way in hell I am not replacing all of it, even if it is a 25 cent O ring. Seems more plausible that the O ring blew rather than the core, but the fix requires same ugly prep. I will snap pics as I get to the box.
For the sake of clarity, I did the TEV [Thermal Expansion Valve] on my SEC last Summer. Evap connections to & from the TEV are external of the HVAC box. I referred to this for reference:

Removal and Replacement of Expansion Valve

Here's one of my pics just above the accel pedal on my 560SEC.

I don't wish this on anyone..

That said, you are goin' in...........

Malc
 

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#15 ·
I had also torn open the side and floor carpets and we are dry as a desert. The origination of the leak is inside the box.
 
#16 ·
Is really not that bad, is just a lot of work. I did it on my Suburban few years ago, I worked every day for an average of 2 hours. The job is very similar with the W126, the dash has to come off and the climate box is not simple on the Suburban either. After two weeks I had it back and running with new evaporator and heater core, AC charged and new antifreeze. I wrote every step I took, every screw I took off. At the end I had 4 pages of steps. I always think of these ugly jobs as just a "matter of inconvenience".

The exact same job I am planning of doing this summer on my SEL because I have a new heater core, a new condenser and a new expansion valve, so you are not alone. The difference is that I do not have to do it, I am doing it proactively, and because is easier to do it now when I have the engine out which means no antifreeze and no A/C Freon. We can exchange notes through the process, but I am in no rush to do mine which means it will be a while to finish it.
 
#17 ·
Well yes this is true. Poor pitiful me, I have to drive the E500 for a month more than usual....

I am more bummed that I have to do it, and we had an extremely nice Spring here in South Texas. Only this week are we seasonably 85-90 with 80-90% humidity but if this had happened back in April-May, it would have been so nice to do a job like this. My first project when I bought the car was dash removal, I did it solo and had no parts left over. I have secured access to a complete replacement box if needed, so It is just a do over.

I figured I will give the sealant one last try but I am not optimistic. I wont even have a chance to begin earnestly working on this for the week, and my parts are not even due to arrive anytime this week. So a different brand of sealant as suggested. Will post results later in the week.
 
#19 ·
Well thanks Ed. Car sat for 24 hours over cardboard, no pressure left and still more evidence of more refrigerant out the evap drains. Parts have shipped....
 
#20 ·
Sitting here thinking (yeah, a "dangerous sport" here sometimes) I feel your pain on the dash removal as I had to replace both the heater core and radiator in my S10 from the dreaded and notorious "Dex-cool mud" plugging both. A PITA for sure but like Ed said, you DO have the 126 dash removal merit badge already and I too if closer would lend a hand
 
#21 ·
Humidity tolerable today, may spend lunch beginning the unbolt process.
 
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#22 ·
So had a chance today to do just about all of the removals. A pillars and
Steering wheel left to do and the Dash is out. Fcp euro delivered the new BehrHella unit today, their warehouse is local, I paid for next week, got it next day.
 
#23 ·
Progress



And I saw this:
 
#25 ·
Didn't get anything done on this today - had collision work to do on my sons truck.
 
#26 · (Edited)
Well the excitement begins today

And let me say, if you remove the crash bar a 18mm wrench removed one line and the 22mm took care of the other. Easy work removing the crash bar. Will work on box tear down this week.



 
#27 ·
Well the excitement begins today

D-D-D-DAYUUMMM :eek :eek :eek

THAT is one job I hope I never have to do, did it on my S10 already so's I know what's involved
 
#28 ·
Also plan to to delete after market wiring, and better route things under console and under the dash.
 
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