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Advice needed on Cooliant leak Behind firewall

4K views 37 replies 15 participants last post by  james sharp 
#1 ·
Guys, another day in Paradise. Took car to local indy shop for the cooliant leak.

1997 s600. m120. 110k miles.

Cooliant leak was located back by the firewall, metal heater hoses are corroded and rusted out that need to be replaced.

it looks like you have to remove the dash to get at this.

if i do this myself, what else would you suggest that I replace when I have this open?

anyone else had the pleasure of this job?

They declined to do the work, they said they werent comfortable to do the work,
 
#3 ·
Taking the dash out is basically a herculean effort; the entire interior needs to be disassembled and removed. I believe the official shop manual has it down as 24 hours of labor. I don't really blame your guy for not wanting to tackle it. I know there are some people on here who'll say it's not a big deal to DIY, but seriously unless you're extremely savvy and very comfortable with literally taking half your car apart, I'd find a specialist.

As bk1 above mentioned, there are W140 specialists who know this work in particular, so you'll want to look into one of them. I believe there's a guy in Brooklyn who specializes in that particular job as well. I use an excellent mechanic in Great Neck, but to be honest he's a two-man operation and I'm not sure he'd be able to take something like this on in a timely manner. Where in NY are you?

While you have the dash out, you'll definitely want to replace the evap core whether it needs it or not; an ounce of prevention and so forth. They're not super expensive and since you have the thing apart anyway there's no reason not to. Heater core too, just for good measure, although they're not prone to failure but again, why not. I dont know what else is back there that tends to fail, I'm sure someone will chime in.
 
#4 ·
This is the "oh god no" area of the coolant lines. You need to fix this. Now. It gives no warning when it fully bursts while driving. You are actually extremely lucky to have a slight leak at first to see it.
 
#5 ·
Have you checked if your car has the flap at the Firewall to access those hoses ,unless that flap was deleted on later models ,I don't know .
If you fortunately have it ,it should be an easy fix .:thumbsup:

This is what you see if you have that Flap opening hatch .
 

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#7 ·
gathering all the videos and info I can. I am in texas, not NY. 40 degrees outside today. not starting this job till i have researched it completely. Once, I have the dash completely part, what else do you guys recommend replacing? I am going to do the heater core, ac evap and the metal hoses that are rusted out. is there any other preventative maintenance that i should do once, I have this open? I am sure this is an all weekend job.,
 
#12 ·
There is a several part YouTube video series under "Mercvideo" which was originally recorded around 2001. I found it by searching "w140 evaporator replacement." The repair was done on a 1995 s500 if I recall correctly. Whoever did this job is a mechanical genius.

I have a '97 s420 and found it very helpful when I had to take apart some of the dashboard. However, I have never attempted the evaporator and heater core replacement on this model. It looks like these items are housed together in module along with the blower motor. I would be afraid of getting everything in this module back together properly before reinstalling the rest of the dashboard.

Taking apart any Mercedes dashboard is a bear. I once had a 300 SD that needed its climate control vacuum pods completely replaced several years ago which required disassembly of most of the dashboard. Not a fun job, and this model is simpler than the w140.

I feel your pain. A decade ago, I had a 300E with the evaporator problem. I spent about $4,000 at the Mercedes dealer on this problem.

Good luck.

Brian
 
#15 ·
Ohhhhh you tooooo, On a 1997 :crying

Dam..... I got the same thing on a clients car.... This client does not want a heater core change...

The question for everyone:

Where do bypass the heater core? I would imagine one basically eliminates the heater tee...

Martin
 
#17 ·
In watching car assembly shows on various channels, most newer cars install the complete dash assembly through the front window (not in yet). I wonder if the 140's were built this way. If so, if you find the main attachment points, remove the front window and go from there. It sure sounds simple doesn't it? Would be a lot easier to work on also. And be sure and take a look at the pods and replace them at this time.
And believe me I am no expert but just thought this approach might work.
Anziani
 
#18 ·
project coming along. Luckily i realized that, you need this dash removal kit I found on eBay for this job. 20.00 shipped. it is an 8 tool set. hasn't been too bad so far. trying to get the 1 piece center console wood piece out without breaking it, has been time consuming.
 
#21 ·
Well, just a minute. If James flatbeds his car to and from Victor and saves many thousands, perhaps it would be worth it. My only concern would be that the car sat outside in Brooklyn before Victor got to it. And my experiences in the NY area would give me doubts.
Anziani
 
#22 ·
This thread highlights some of the crap that keeps me up at night. I've fixed every dang thing this car, a 97 s420 w/ 65k, needs with no cost spared. Every time I take her out, I wait for the next shoe to drop... this is no way to live! The expense this eventual failure(s) will require would be the last straw. What next; tranny or motor? The latest; just got done with a full rear end rebuild.

I do love this car but Jesus, another big nut to swallow without the expectation of some serious longevity? The labor to fix as I go has kept me in the driver's seat for five years now. The help from this board is the only psychotherapy that keeps me from flinging my car keys in a river. Well, and a thick wallet....

Is there any kind of inspection to see if these are in my near future?
 
#23 ·
Is there any kind of inspection to see if these are in my near future?
Evaporator core? No real way to tell. One day it'll work, the next it won't. Only advice I've heard to help keep the evap core healthy is to replace your A/C driers every couple of years, but I don't know how much that really does.

Now, your car is a 1997, and I believe the cores on the later cars were less prone to failure, but again that's just anecdotal as well; I've never heard anything concrete on whether the issue was fully solved (like it was with the biodegradable wiring).

Two things to keep in mind for your car; age and mileage. On the one hand, your car is twenty years old and I'm assuming you're not the original owner. It's entirely possible the car has had the core replaced already. On the other hand your car has very low mileage, which means the problem could still be lurking, as it may not have been driven enough yet to induce the issue.

My father bought a brand new 1995 W140 which needed the evap core done in 1999 -- less than five years old -- with like 50,000 miles on it. The car was still under warranty when it happened so didn't cost anything, but it would have been a $5500 job otherwise.

So depending on whether you go by age or mileage, your evaporator may be fine, or right on the verge of breaking.
 
#24 ·
Thanks Thom.
Second owner at 54k. Have prior records and no such luck. Superficial stuff and even some scams by the dealer. She sits a lot used mainly for long trips (4-500 miles). Long list of repairs and maintenance I've done but lots more to do such as shocks, water pump, belt, related wear items under the hood. Are they broke? No, just preventative measures.

With purchase price and repairs, I've got $16k into her and realize there is no coming back from that. But that's why I just keep keepin on (as the saying goes). I've had several older cars as projects but this one impedes me from moving on to another one. A time will come when I need to just cut her loose but I just hold out hope she'll get a second wind. There's no beating on this one. Gets treated like a garage queen. Just hope someone treats me half as well when shit starts breaking and falling off me.

Going to flush the cooling system again as minor prevent.
 

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#27 ·
Doesn't one figure $2-3K a year in maintenance? After 5 MB's that is about what I have spent. But then look at the alternative. One buys a new car and takes a huge hit the first 2-3 years in depreciation. That is never mentioned because one doesn't realize it until he trades in said car. My neighbor was typical. If he had to spend more than $1K in repairs, he ran down to the dealer and bought a new one. Never mind he was losing over $20K every two years. Personally, I would never buy a new car (unless I was loaded!)
Yes I am driving a 20 year old car and so far it is perfect (after spending the maintenance money). You are damned if you do and damned if you don't!
Anziani
 
#28 ·
I figure about $1500 a year in maintenance for my car. You have a 600, so you're going to be on the high side but yeah, you're right about the economics of it.

There are upsides and downsides to driving an older car. Frankly most people buy new cars because they simply don't know any better. A friend of my mom's gets a new Audi every couple of years. We were having dinner at one point and she started going on about how she needed to get to the dealership soon to buy a new car because her current one had 40,000 miles and she was starting to get nervous driving it. She genuinely believed that it was going to fall apart and leave her stranded on the side of the road if she put any more miles on it. I tried to explain to her that these cars are good for 100k miles and then some but she just gave me a blank look, like I was a conspiracy theorist explaining that jet fuel can't melt steel beams. On no level did she believe anything I was saying. In her mind, you take your life in your hands driving a car with more than 50k miles. I had to drop the subject because it was driving me nuts.

Personally I prefer the aesthetic of older cars to almost anything being produced today; it's not really economics. Even if I won the lottery tomorrow the only new car I'd buy is maybe a McLaren or the new Maybach 600. But otherwise all the other cars I'm interested in are vintage.
 
#29 ·
There are certainly older vehicles where you may end up in a financial "win" by keeping them around, such as certain ones from certain Japanese makes, but not with older German cars from perhaps the 1970's onward. I have owned about a dozen older Mercedes during the past few decades. I generally like them for two reasons: styling and safety. Even with the youngest w140's approaching 20 years old, I still feel much safer with my family riding around in that model versus many newer vehicles. If you compare the crash test video of a w140 versus some current mid-size sedans, tell me which one you feel more comfortable if ever faced with that situation?

Pretty much every Mercedes car dating back to the 1970's seems to have at least one fatal flaw in their design from the following categories: rustproofing, electrics, engines or other mechanicals. I say "fatal" because the prowess of German engineering requires that a car be put together like a jigsaw puzzle. As such, these flaws are often in obscure places and very expensive or time consuming to correct, sometimes requiring extensive disassembly of the engine (e.g., M117 timing chain issues) or body (e.g., evaporator replacement). Sometimes these flaws combine together to create a true nightmare (I am thinking about an early 2000's S-Class or maybe an early w210 with the straight six which is known for head gasket issues and structural rust). I cannot think of a single Mercedes model from the 1970's onward that did not come with some huge flaw in its design. The vaulted w123's had horrible rust and vacuum issues--their engines would last for 300K or more miles, but their bodies would literally crumble away (as did many cars from that era). Their vacuum problems meant that they often wouldn't shift right or shut off. Even with the venerable 300SD, the early ones (w116) had a horrible Chrysler designed air conditioning system (mine did not work) while I remember tearing apart the dashboard in my w126 300SD because the climate control vacuum elements both deteriorated and were put in impossible locations to access. With the newer models, I still hear about significant engine problems as recently as several years ago with the whole balance shaft issue that spanned multiple engines and model lines owing to a basic gear tucked far away in these engines made from bad steel. Seems like most of these problems originate when Mercedes decides to become innovative with how they make their parts, such as making internal engine parts from plastic and their wiring harness insulation from the same stuff you put in a salad (i.e., soybeans). And while parts availability with older Mercedes is very good, I often find myself hunting around on the internet to place a parts order that will not cost the entire value of the car. The factory may provide support in parts availability but certainly not in their pricing.

This is not just Mercedes. Germans seem to have a problem with making basic systems function properly, and later owners outside of warranty are often left holding the bag to sort out the mess. In my opinion, Audi may be just as bad. How many years did Audi struggle with its bread and butter engines consuming excessive amounts of oil? I am not even sure if this issue has ever been solved.
 
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