'80 300SD antifreeze leaking; bad hose? And what is THIS thing (novice, go easy)

[WrightSounds]

It's been uncharacteristically cold here in Portland, OR for the last week or so. Temps dropping to the mid-20's F˚ by the time I'm up in the morning. The 'ol diesel has been starting up pretty nice but I thought I'd check the coolant level. It was a bit low so I topped it off. A few days later, after more cold (for here) weather, I checked again and it was low. After some investigating I noticed a pool of coolant collecting under the thing in this picture (what is that? Heater?)



I'm guessing (hoping) that's it's a couple of the hoses that need replacing. I can see where coolant has leaked out where the hoses make connections. Here's a good pic of what I'm seeing:



Two years ago the previous owner had the following work done to the cooling system:
*replaced Fan clutch, water pump, front crank seal, alt belts, p/s belt
*R&R radiator, replaced mounts

Not sure what most of that means but it doesn't look like any hoses were replaced. The car has been heating up fine (I replaced the thermostat a couple months ago) and not running hot but I'd like to nip this problem in the bud before it escalates.

Any ideas or help for a novice? Thanks in advance guys!
-Matt

[Malpaso44]

Hey what you're looking at is called a climate control servo. You have an alluminum updated version. I have the original plastic servo which is leaking now. From the pictures it seems as though it might just be leaking from that lower hose.

[WrightSounds]

Hey what you're looking at is called a climate control servo.

Ok, cool, that's what I thought. Thanks for your input. I'm going to inspect it more as soon as it's not FREEZING outside and daylight (my wife drives the car to work daily). I did see some moisture around the screws from where the aluminum is attached to the plastic top of the servo. Also, in the second pic, you can see some wetness on the curved hose that looks like it came from the hose right above it that goes straight into the servo.

Looks like I'll try my hand at replacing those hoses.

Anybody else have .02¢ for me 

[scraf]

Spray those clips a.s.a.p. with WD40 or something better, and have a 7mm ( think it's a 7mm ) socket ready for action if possible.

[WrightSounds]

Spray those clips a.s.a.p. with WD40 or something better, and have a 7mm ( think it's a 7mm ) socket ready for action if possible.

Yeah, definitely some corrosion on those clamp bolts. Any idea how much antifreeze will pour out of the hoses when they're removed? Or any idea where instructions are for this job in the Library's manual here. I've looked twice and can't find it. Thanks!!!

-Matt

[JasonP]

300SD / '80 / Engine Manual / Section 20 - Engine Cooling

http://handbook.w116.org/engine_78_d.htm

[Hemersam]

Sorry to say, but it's one of your worst nightmares  . Just ask any American W116 owner.
Hemersam

[WrightSounds]

Sorry to say, but it's one of your worst nightmares  . Just ask any American W116 owner.
Hemersam

Uh, can you enlighten me a little 

[oversize]

It seems to be wet well above the hose clamp, which may indicate the servo is leaking.  It seems many US owners have complained about the system to the point where some would prefer the manual system.  Not sure if this is the main problem, or if there's a whole series of problems that can occur.  Sounds like yours has been pretty good until now.

Has anyone rebuilt one of these servo units before?

[WrightSounds]

It seems to be wet well above the hose clamp, which may indicate the servo is leaking. 

Yeah, it's really just where all the hoses connect. Right at the rim of the hoses is green from the antifreeze. Again, I'm guessing (hoping) that the hoses have dried up and cracked where the clamps are. There is some moisture near one of the screws that holds the bottom black half to the top aluminum portion but that may be from the short, 2" hose that's right in front of it, leaking/spraying coolant. There's evidence at the end of that 2" hose that it's leaking.

I've been reading about the servo unit and what seems to be a common problem (like Malpaso44 said earlier in this thread) is the servo cracks, then leaks all over the electronics of the servo, and systems fail. But I've got the aluminum servo instead of the plastic one so hopefully it's fine. From my novice inspection it appears to be intact. The heat/defrost work great. The car runs at normal temp (90˚c).

I'm just trying to have some light shed on the procedure for removing and replacing the hoses.

[scraf]

... um

Possible hiccups for the procedure:

The jubilee clips not wanted to play ball. ( see my earlier post )

The tubes not wanting to separate, patient force might be required, or a knife if a replacement pipe is available.

Finding a replacement piece of pipe. That would be either going down the "try and find the part from a shop" road, or, as in my case, know places where loads of rubber pipes are lying around from previous dismantlement's / repairs.

[WrightSounds]

... um

Possible hiccups for the procedure:

The jubilee clips not wanted to play ball. ( see my earlier post )

The tubes not wanting to separate, patient force might be required, or a knife if a replacement pipe is available.

Finding a replacement piece of pipe. That would be either going down the "try and find the part from a shop" road, or, as in my case, know places where loads of rubber pipes are lying around from previous dismantlement's / repairs.

Thanks Scraf! And I would guess I'll have to drain all the coolant first, or no? Again, pardon my newbie ignorance...I build and repair guitars, not cars 

-Matt Wright
www.WrightSounds.com

[Casey]

Why it's a nightmare is in my mind threefold.

1.  The original plastic-bodied servos will spontaneously crack with age sometimes, at which point you'll lose massive amounts of coolant and notice an overheating engine in short order.

2.  The mechanics within the servo stop working to different degrees, making adjusting the temperature partially or completely impossible.  In one of my cars, I can turn the heat up fine, but I attempting to lower the heat has no effect.  I have to turn off the car and let the servo "park" and then start the car again and be careful not to turn it up too high.  In most of my cars with automatic climate control it simply does not function at all and I have to choose between "off" and "defrost" (max heat).  In my first W116, a 1980 300SD, it is not possible to turn off heat at all - the servo is entirely gummed up.  So I switching the system into "off" results in no fan running, but very hot air is constantly trickling in the vents.  I can close the vents, and still feel heat radiating from the dash area and center console.  If I play a cassette in the radio, it gets so hot I can barely touch it upon ejecting it.  This is clearly not ideal for the various components in the dash.  In the cars I have with 100% perfect functioning ACC, the maximum heat setting produces less heat than the maximum heat setting in a car with manual climate control.

3.  It's not just the servo - the system is a complex arrangements of a multitude of vacuum lines that develop leaks over time, the control interface on the center console which can be problematic, and various other parts that are hidden away inside the dash.  The design of the fresh air flap is such that even if it's ridiculously cold outside and you have the heat set on maximum, it will always allow a certain percentage of cold air in from the outside.  The system is very tricky to diagnose and the components are quite expensive - a new servo will run you around $700 to give some idea.  Mercedes did not design this system - I believe Chrysler did (but I could be mistaken) and then licensed it to Mercedes-Benz.

This is *not* at all a US-specific problem, nor does it affect "any American W116 owner" by any means.  Automatic Climate Control (ACC) was standard in all US-delivered 6.9 and 300SD models, but it was not standard in any of the other W116's - manual and automatic systems were available in 280SE(L)'s and 450SE(L)'s, and I think you'd be pretty hard-pressed to find ACC in any US-delivered 280S.  Automatic Climate Control was also an option available in any other market as well - it's a factory option in the euro 6.9 I'm considering purchasing.  It's simply more common in US-spec cars as are sunroofs and various other options.  With exception to the US-spec 6.9 and 300SD (which was ONLY available in the US market), it's simply something that a larger percentage of Americans were willing to pay a premium for versus the rest of the world which tended to be more practical.  I believe this is because in America, new Mercedes are quite expensive compared to other brands of cars and are more exclusive/distinctive, whereas in other parts of the world they are a more common and affordable option compared with other brands in the local markets.  It may also just be a more common aspect within our culture - I rarely buy new things in the interest of saving money, but when I do, I go all out and max out the specs as much as I can.  Both of my US-spec 450SE's have manual climate control for what it's worth.  Remember that the 300SD was a pretty high-end car in it's day, costing almost double the price of a 450.

I'm specifically very interested in all the options that were available for the W116, and try to collect them all.  My garage is full of various rare parts like a column shifter setup (versus the usual floor shifter), rear headrest sets, seat heaters and switches/wiring, French headlights with yellow fog light reflectors, orthopedic front seats, etc. and my primary motivation to buy the 6.9 I'm considering is to get the reclining rear seat option.  I've even got a couple cars that have 100% perfect functioning ACC systems, which is rare, and I've pulled one of those uncommon aluminum-body servos like you have from a junkyard and have it at the ready should one of mine crack.  However, ultimately my goal is to replace the ACC setups with the manual system transplanted from other W116's.  It's one option that I have no interest in - too many issues and too prone to problems.

[Casey]

Thanks Scraf! And I would guess I'll have to drain all the coolant first, or no? Again, pardon my newbie ignorance...I build and repair guitars, not cars 

Your car has incorrect coolant in it anyways - the green stuff is corrosive to the aluminum parts of the system and can cause pretty extensive damage over time.  You can get away with just putting a drip pan under the car and changing the hoses without draining all the coolant, because most of the coolant will stay in the engine and radiator.  If you want to properly drain the system, there is a coolant drain plug on the bottom of the radiator as well as two on the bottom of the engine (actually on a 300SD, there might only be one, I'm not sure, but there are two on the V-8's - one on each side).

What I would do if I were you would be to use the drip pan approach and get the hoses replaced and the system free of leaks, topping the system off with just water as needed to test and ensure that you've got all the leaks addressed.  Then I'd fully drain the system, disconnect the big hose that comes into the top of the radiator and fit a piece of pantyhose over it and reattach (to serve as a filter to catch debris before it enters the radiator that will be coming loose), fill it with water and some coolant flush product, drive it around for a day or two, drain the system again and remove the pantyhose and any debris it may have caught, then fill the system with the proper blue Mercedes antifreeze that you can pick up from your local dealership.

I'd probably proactively replace your thermostat at the same time.  They are inexpensive and often not functioning correctly leading to improper engine temperatures.

[scraf]

Thanks Scraf! And I would guess I'll have to drain all the coolant first, or no? Again, pardon my newbie ignorance...I build and repair guitars, not cars 

There's an old Rock'n'Roll saying from the roadie world "There's those that know, there's those that don't know, and there's those that don't know they don't know". Only the third party of that lot are troublesome.

Draining the coolant is probably the least messy way to do it. That would probably be a 13mm ( maybe a 17mm ) socket on the underside of the radiator.

...  I'm not sure if it's totally necessary to do so though, guess it would depend if the parts you need to change are higher or lower than the radiator and engine tubes.

Sorry I can't be more specific, but my W116 doesn't have one of those things.