I think you might have been “goosed” by that dealership.

W210s are notorious for having leaky evaporators.

The right way to fix it is pull the dash and change the evaporator.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

There is a Pelican parts Wiki paper showing how to changed the evaporator:

PeachPartsWiki: Replacing the A/C Evaporator Coil

There are also YouTube videos. It's a big job, requiring lots of patience.

I agree with JB about the evaporator but before jumping to that diagnosis get a UV light kit with some dye and do leak detection. If nothing is found in the engine bay or by any of the lines then, well, you have an EVAP leak. They aren't fun to do!

I run some sealant in mine, sometimes it works sometimes it doesn't. Until it doesn't fix the leak and I'm adding it every week, I won't pull my dash.

__________________
Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

jay bob, LOL!!! "goosed!" if that is the case, i'm ok with it, i got for an amazing price. i'm not 100% on the workings of the W210 heater core(s) with dual climate control. maybe someone can post a link for a diagram for that?

what i do know, is the duo valve has a good bit of "smack marks" on the top of it where people other than myself have used tough love to get the system to blow cold. when i did the same, the drivers side started blowing cold right away. i drove it to work yesterday, and sat in the parking lot with it at idle for over an hour at lunch, and everything worked perfectly. it actually blew so cold i had to keep lowering the fan speed.

i will start with pulling the duo valve apart and checking it for gunk and reassembling and go from there.

it may have nothing to do with the heat blowing out of the floor vents, but as i said earlier, maybe someone can show me how that would be possible?

thanks again for all of the help!!!

__________________
'92 300D 2.5
'99 E300TD

100% the fault is the duo valve sticking.

While some people have had marginal success whacking the duovalve with a mallet, disassembling and cleaning, etc., these are often short lived solutions. Best just to replace with new part and be done with it.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 156k miles
06 E320 CDI "Rutherford", Black on Tan, 173k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 143k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 67k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I might have been a little premature on a full evap job needed. However if you end up having to keep topping it up then that’s probably what you’ll need. Like Jake says check with a UV light around the engine bay. If it’s clear, then slide underneath and shine the light around the transmission. The evaporator drains dump out on top of the transmission so if there’s a leak it will show up there.

The dashboard is not as intimidating as it looks.

My thread on the issue, complete with links to a guy in Taiwan doing it and then an official MB video that shows the process for dash removal.

W210 compressor seized

I did this 2 years ago now and it still works perfectly even in the insane 95 degrees/80% rh Columbia summers. I have not had to touch it since.

And another tip on the dual valve, there are getting to be a ton of gas W210s and other late 90s MB in the junk yards now. The gas model uses a similar dual valve that only has 3 ports. Turbo Diesels have a 4 port valve so the coolant circulates back to the system when the valve is closed, instead of just being blocked off like it is in the gas models. I didn’t realize this until I got it home. Fortunately the difference is another piece in the sandwich and longer screws and longer valve poppets. The part that fails is the sealing surface, which can be replaced without pulling the whole valve or draining the system. I was able to clean up the tips of the valve poppets using a little Brasso and put the whole thing back together.

I was getting half hot half cold because one of the valve ports was sticking. I was able to confirm it was the heat because the parameter 03 or 04 on the display (L/R heat core temps) was shooting up into the mid-100s.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

jay bob, thanks for the description on the inner workings of the duo valve! i had no idea the turbo diesel ones had 4 ports and gassers 3. you just saved me a trip to the junk yard.



however, i think i found the problem....(see pic) one of them, the closest to the fender, was flipped completely upside down (pointy side up) inside the bottom half of the valve.



3 questions:


1. are the pintles replaceable?


2. are they repairable ie. adhesive or solder


3. is it possible to temporarily bypass the duovalve so that the vents only blow cold, but do not disrupt engine cooling operation.

Attached Thumbnails

 

__________________
'92 300D 2.5
'99 E300TD