White residue - looks like it's coolant related
 

Running a diesel purge at open throttle seems to have surfaced a few issues. First the injector return hoses burst open and had to be replaced. Now I have found this residue in the engine bay (valve cover and pictured hose mainly).

The radiator took a liter of distilled water before it filled to the top of the filler on a warm engine - it had zero oil residue floating on the surface. The engine oil on the dipstick also looked normal. No oil leaks anywhere and zero oil consumption.

The car has its original Behr radiator and severely rusted oil cooler. I plan to have the radiator re-cored. I suspect the pictured hose may be leaking. Diagnosis/ thoughts are welcome. Thanks!

I'd do a Citric Acid flush before letting anyone touch that radiator, few can re assemble them sans leaks these days and that one isn't very rusty .

Remember to have the HEATER ON and drive it a while once the cleaning mix is in ~ you're not just cleaning the radiator, you're cleaning the entire water jacket that's coated with the rust silt .

This might be coolant additive residue (evaporation or rather small droplets flung around by the fan at high revs. Looks there is some on the fan shroud too).
Check for leaks (after pressure build-up, when the engine has reached oper.temperature-the upper hose should be firm to touch) on the radiator and the weep hole of the water pump (engine shut, of course).
Also this could have happened if some coolant(or just vapors) escaped via the overflow tube(on the filler neck of the radiator itself).
I'd also change the rad cap if it's the original one (get a Behr/OEM with the same pressure setting).
When was the last time you had checked the coolant level before the purge operation? It might be just a coincidence.

The radiator was full at cold temperature when I purchased the vehicle 700 miles ago. It's lost 750ml of coolant since then.

At peak operating temperature, the hose (in the 2nd picture) was bubbling with a mild leak where the translucent hose meets the nut. It is likely the fan blew the fluid onto the valve cover as it travelled upwards. What hose is this? Is a leak common?

Were I to re-core, I would do it at Aaron's radiator. They specialist in metal classic car radiators and have a pretty decent reputation here in the UK. They even have another diesel rad in their workshop currently.

Haven't heard of a Citric acid flush done of a W114/5 but am open to try. Anyone documented how to do one on a /8?

Do a coolant system pressure test before you start replacing parts. No need for a fancy-smancy one as the /8's use a plain generic cap. 1 bar/15PSI.


Attachment 153873


No need to spend a ton of money. You can usually get a loaner from auto parts stores.

Thanks for the advice. I'd like to know what's causing this first, so a pressure test may be prudent, followed by a flush. I've filled battery water for now.

A couple pictures that point to the issue and may offer clues. Can anyone share what the translucent hose is called? I suspect the leak is emanating from there the pictured joint

Translucent hose is the vacuum pump exhaust air hose.
It is just a vent for air from the vacuum pump that goes to your air filter.

The dried coolant on the translucent vacuum pump vent hose, radiator hoses,and radiator is most probably from leakage of coolant from the top radiator hose when the system is pressurized.

The MB rubber hoses remain quite pliable for an amazingly long time.
The top radiator hose may be long enough to allow you to trim an inch off the hardened hose end, reattach the trimmed hose to the top radiator nipple, and get a better seal.

My year and model has a different arrangement of hoses. But, when the Hoses were removed the Aluminum casting where the hoses seated had deep pits of corrosion on them.
The pits were causing a seeping leak on one of the hoses.

Not an issue with the citric acid flush in of itself; but in the past some have found that the rust or what ever residue was in the cooling system had actually been plugging up some small holes. And as a result of that people have found their Heater Core leaked, a Core/Freeze Plug leaked or the Radiator leaked.

Although this is problem that happened back when people only put Water in their cooling system. Often when people did a coolant flush it loosened the rust in side of the Engine Block and that rust would keep coming off for Months and Months and Months plugging up the Radiator and causing overheating.

I have owned a car since 1968 and the plugged radiator after a flush has happened to me and also to my Father on one of his Cars.

Citric Acid Cleaning & Flushing
 

That's why it's so important to DRIVE it for a while ~ if the radiator's tubes clog after flushing it means you didn't do the job fully not anything else .

Yes, I had a welch (? SP ?) plug begin to weep after flushing my very fist 300CD, the entire cooling system was ruined because the damnfool I bought it from had filled it with tap water after bypassing the failed & leaking evil Klima I servo from hell .

If it begins leaking because you flushed it, it was bad and waiting to do you dirt .

My w124 was showing a similar spray pattern as the first pic in your original post. Radiator had a pinhole leak on the driver's side, down low. The cooling fan was picking up the leaked coolant and blowing it all around. The inside of the fan shroud was covered in that same chalky white mist. New radiator cured the problem. YMMV

I agree with the part in red. But, what has happed to at least 2 others in the past they thought that their job was going to be done over the weekend. If you happened to look at past threads where I posted the warning I recommended planning some backup transportation to work if their Mercedes was there only Car.

For myself If my Coolant System is working properly why would I do a flush and risk the chance of precipitating other issues.

I mean if our heater core starts leaking you have a serious job ahead of you.

Since those early days I have only used flushed if I was using some sort of block sealant and then I just used something mild like the Auto Parts store sells.

Anyway that is how deal with it personally.

In the case of the original poster he is in the UK where it is a good deal cooler. I live in Southern CA where today it was 91 degrees F. If I am not overheating in this weather why would I bother with a coolant flush even if there was some residue in my coolant system?

Valid point. Even with what appears to be a very small leak somewhere and our relatively mild summer temperatures, I have hovered around 180-190 degrees and never exceeded this. I appear to have a couple options:

1) Leave things alone and top up with coolant occasionally. Enjoy the benefits of living in a temperate climate for 90% of the year.
2) Perform a citric acid flush prior to the radiator re-core (new radiators are NLA)
3) Re-core the radiator and call it a day

Ignore a problem at your peril .

I too live in So. Cal., it was 109* F in Pasadena before noon to day, at noon 0:clock it was 99* F just South of down town L.A. .

I like to drive in the Desert and never need worry about by cooling system .

I was able to take 3 videos further highlighting these symptoms:

1) This is BEFORE the car is started. Hasn't been driven for 5 days so the radiator is dry.

2) This is AFTER a 70 mile road trip. Car maintained its temperature but you can see the leak. Could be the upper hose as ALEC shared as the coolant does appear to be concentrated in that area.

3) Wetness on the venting hose.

Before a citric acid flush, and radiator replacement (which still may be needed), I would recommend ruling out a leaking top radiator hose.


Clean up the area and the mating surfaces very well:

Warm soapy water and a stiff nylon bristle scrub brush can dissolve and remove most of the crusted coolant residue on the radiator.

The hose clamp may need a soak with penetrant as it looks rusty.
It should be eventually replaced with a Norma style clamp.

The hose may be difficult to remove.
Gripping the hose with sliding jaw pliers and giving it a twist can break the adhesion between the hose and the nipple.

Warm soapy water and a terrycloth rag will remove any internal hose residue.
You need to clean about three inches into the hose, just a bit past the bulge in the hose end (due to the flared part of the nipple).
The hose end may need to be trimmed if it is too hard or has a hidden split.

NEVR DULL wadding polish will clean the hose nipple quite well, without damaging the surface.
Avoid the temptation to use sandpaper or a Scotchbrite pad.
Fine steel wool would probably be okay.


Once everything is cleaned, reassemble and test for leaks.
Hopefully this will cure the leak.
If not, at least it will be easier to track down the leak with clean surfaces.

Weeps & Seeps
 

As Alec said, you need to diagnose this before making any assumptions .

There's a hose loosening tool that's a screwdriver handle with a round spike on it that has a right angle bend just before the pointed tip ~ the better ones have a slight curve to help work it around the hose nipple on the radiator because they're easy to damage ~ I'd nver suggest a DIY'er to use the large water pump pliers here .

Clean well and re attach trimming as necessary then see what's what .

No matter what, clean the cooling system properly before you touch / remove that radiator ! .

Looks like peril was a good adjective to describe this!

Driving within city limits on a cool day (60-70 degrees F), I noticed the temperature gauge fluctuate 25% of the entire range of measurement. Never exceeded the pictured temperature.

The car got me home, which is when I noticed this (video 1) with the car running. And switched the car off immediately to see the car really let off some steam (video 2).

Should I still focus on the upper radiator hose? Seems like a more sinister issue.

? When it heats up like this, have you been running the heater full on ? .

No matter what you need to take the radiator out for service, before you do you really should give it a Citric Acid flush or you're going to be fighting this for a long time to come .

This was the first time this happened - the car got me home which is when I took the videos above. The heat was not on.

I plan to flush the radiator as a precaution though I have never done this procedure on a car before.

Running Too Hot
 

Any time you think your engine is running too hot you should immediately turn the heater (NOT the defroster ! :eek:) on high and open all the windows .

Follow the instructions on the Citric Acid flushing, it's simple and requires few tools, just some time and very minimal effort on your part .

Thanks Nate - what’s the reason why we should turn the heater on?

Was planning on following theses instructions. Not sure when I should turn the heater unit on during this?

https://www.dieselgiant.com/mercedes_citrus_flush.htm

Cooling System Cleaning
 

The heater's core ("matrix") is mounted _below_ the hose connections so rist silt and solder bloom, oily good and so on all settle into it ~ unless you lave the heater on FULL as you're flushing it will trap bad stuff in sde it t, stuff that will come loose and contaminate the clean fresh radiator and coolant you're putting in .

I find that flushing in Summer with the heater on full does the very best job of cleaning out all the crud you want out .

Yes, the method you linked to works well, I agree that it's *very* important to reverse the water flow as your hose flushing, you'll understand when you see brown/red crud flowing out after it was running clean as glass in the other direction .

I don't remove the thermostat unless it's bad and needing replacement .

The little electric coolant pump is simple to connect to the battery and let run as you're flushing, this helps insure every part of the cooling system & water jacket gets fully flushed .

My self, I get the engine full of the citric acid mix and drive it at least 1/2 hour to breakfast, then I drain and flush it , my cooling system is very clean indeed and my heater works tops and my AC blows 60 degree air in Death Valley with the engine at 90 degrees F .

You can buy citric acid off the internet at 1 10th the cost of Mercedes little bottle, it's used in backing and candy making so if you live near a city you might find it locally .


I bought a large box of it and use it on all my vehicles and my brother's old truck and his Mercedes' too....

Many thanks for the advice. I've ordered the citric acid and a new oil cooler. The old one is so rusty, I get tetanus just looking at it.

I plan to check all the hoses. That aside, is there anything that I should renew or replace while I have the radiator and oil cooler out? I've already changed the fan belts and the thermostat worked well enough to warn me about this issue.

Replace the waterpump with a MB rebuilt unit, if it has been a while.

Use a slim counterhold wrench when removing the oil cooler lines from the oil cooler.
Replace the oil cooler lines.

If you have an automatic, replace the transmission cooler lines.

Cheers! Got a link or a part number for the oil cooler lines handy? (Can't locate them on Pelican)

I went ahead and ordered a new oil cooler # 1081800265- got a new one for £150

Also, I suspect I will need the following radiator mount kits? Part# 123-500-00-12-MBZ and Part# 114-500-01-12-MBZ

Have you done the pressure test, which is the first thing you should have done?

While system is under pressure, spray soap solution on suspect areas to pinpoint exactly where the leak is from (this won't work on the heater core since you have no access).

As for the citric acid flush, on an old vehicle like yours there is a possibility that after the flush, new leaks may develop in the radiator or heater core that was not there before. Be prepared to change the heater core if this happens, or bypass the heater core when you do the flush if it is not currently leaking.

What year and model? The oil cooler on my 83 and 85 is aluminum and painted black. Aluminum do not rust! However, it will oxidize if the paint is gone.

For your /8 you need part # 114-500-01-12. This kit has the "doughnuts" required to secure the radiator.

While you have the radiator removed, it would be a good time to replace the short section of hose between the lower hose and thermostat housings. It's a bit of a bugger to replace even with the radiator removed.

It's a 76 240D W115. Pressure test was planned pre-leak but its clear now that the radiator has to come out. The donuts are part of the kits I've linked above.

I'm getting conflicting information on the flush - it's been suggested to citric flush the radiator with the heater on full. Now I'm hearing its best to bypass the heater core?

PAY ATTENTION !
 

No one said not to flush the heater matrix ~

You do the flushing and cleaning first and foremost then you move on to repairs and parts replacements .

If the heater begins to leak, the last step is to add one tube of "Alumaseal", it's a powder that works amazingly well and cannot clog anything .

https://www.goldeagle.com/product/alumaseal-radiator-stop-leak-powder/

Everyone has their own favorite stop leak, this is the only one used by all three American auto manufacturers .

Use the correct G5 coolant mixed properly : 60% distilled water and 40 % coolant .

Never, EVER use tap water ! .

If, after all is said and done, you can by pass the heater but be aware that leaving it dry will make it worse as it just sits there empty .

Anything that begins weeping or leaking after the Citric Acid flush was BAD ALREADY and was just waiting to fail and strand you with no warning .

I'd suggest a NEW M-B water pump if available, find the correct part # and search for it, the rebuilt will be the same P/N with an ' X ' added to the end .

As mentioned, NOW is the time to replace every single coolant hose you can, get them from M-B if at all possible, once you have the correct P/N's you can search E-Bay.de etc. for them .

That by pass hose is indeed a bugger to replace, I'd have a large square bit of flat glass and some 1,500 grit or finer wet/dry abrasive paper of valve paste to polish up the meeting faces of the various alloy coolant parts you're about to take apart, trust me they'll be corroded and will want to leak when you re assemble them .

Some years of OM616 use rubber O-Rings between these alloy pieces, again you'll be wanting to get the best ones possible, M-B if available and yes, it makes a difference .

Do the pressure testing after the entire system is clean and don't be surprised when the hoses weep on their nipples, just take apart and wire brush until perfectly clean and bright metal is visible, chip away the built up whitish corrosion .

I've been through this in all my N/A Diesels, once done I've had no furture cooling system weeps, leaks, over heating, coolant use and so on .

It's German so you have to take it back to 'As - New' condition before you'll be done with it ~ mostly time and effort, why the DIY'er has better results than most shops .

Your radiator and heater core is 43 years old! They don't last forever and deteriorate faster if the coolant maintenance was not kept up, which looks to be the case by your pics.

If you are going to citric acid flush the heater core, there is a possibility you will get a leak afterwards because the acid will etch away sediments and corrosion that could cause a new leak.

I would not trust these stop leak products. They may work on very small leaks but not on bigger ones.

Outside of the upper and lower coolant hoses, do you recommend replacing any others hoses specifically? Names or part numbers will do. The water pump is surprisingly inexpensive, so I may replace it preemptively as well.

Appreciate all the guidance here.

The Bolts that hold the Water Pump on are exposed to the coolant on the other end and they apparently rust in place. It is not unusual to have one of more bolt heads snap off and there is not a lot of room to drill them out without removing the radiator and so on.

When one guy on another forum had some of the bolts break of I recommended removing the other aluminum housing that the water pump mounts on so that he could drill out the broken off water pump bolts. It turned out in this case to be bad advice because he also broke some bolts off removing the housing.

I will leave it to you to read up on if there is ways of reducing the chance of the bolt heads breaking off.

Yes, prepared to deal with that with the radiator out. I've purchased Kent Bergma's stainless steel bolts to replace them with, which should solve this issue permanently.

Here's the video I used to learn about this:

https://www.youtube.com/watch?time_continue=416&v=AEHD_OT9gAU

Also, found another hose that I may have missed. Worth changing?

https://www.pelicanparts.com/More_Info/1158311094M22.htm?pn=115-831-10-94-M22&bt=Y&fs=0&SVSVSI=3196

Citric acid flush complete, using dieselgiant's instructions. Even left the solution in the system overnight for a thorough clean. The result was positive (so far!). Smelly, lightly discolored solution was drained out. Nothing quite as drastic as described in earlier posts. Definitely not dark orange colored.

We haven't pressurized the system yet (waiting on the re-cored radiator) but my mechanic and I don't believe this cooling system to be corroded or in poor condition. Once the radiator is restored, we will install the new dealer sourced thermostat and housing gasket, water pump, hoses (X4) and new oil cooler.

Blue color coolant mix will be the last to go back in. My old-timer mechanic swears by its anti-corrosive properties. Hopefully, this will be the last time we need to touch the cooling system for years to come!

Pictures
 

Was able to get some pictures today.

Pictures 1 & 2 show the thermostat pulled from the housing. We found this black severely degraded and disintegrated rubber hose stuck inside the housing (pictured as it was found). It's clearly perished but we have no idea where it came from or how the system managed to cool with so much coolant flow restricted. Any thoughts?

Picture 3 shows you how clean the inside of the water pump housing is. (We haven't touched it)

Picture 4 and 5 show the factory installed water pump. I find it amazing that a piece of machinery can last 43 years and still run without any leaks. Simply amazing! How did Mercedes loose its way?

-the thermostat is broken (look for Behr or Wahler with the same setting). "Boil" before install.
-somebody had put the rubber cutouts under the thermostat to (try to) block the smaller circuit(I think one can see the imprints).This might have resulted in the breakage. Or this "modification" was done as a remedy for the already broken thermostat.
-#3 is actually the water pump housing.The vent metal line tends to block. Was available from Febi with the hollow bolts ,reasonably priced.
-Scredriva,while you're there can you check the water pump housing for a logo or brand name? It would be interesting to know who the OEM was.

The proper coolant is G05 (available by Comma- https://www.commaoil.com/passenger-vehicles/products/view/354 ) ,yellow.
Or G48 (blue) . Both are HOAT, G05 lacking 2-EHA salts. Both MB 325.0 certified.

Will do Vox.

Thermostat and seals on their way from Stuttgart. Do I still need to "boil" the thermostat, whatever that means?

Can't imagine why they would try to block the smaller circuit. I can check the vent metal line to see if its blocked. Or should I just replace it preemptively?

Cheers!

It's advisable to boil the t-stat in water to verify its proper operation (a dvom with thermocouple will do).Try to keep the t-stat raised so it is not in contact with the pot bottom(use a hook or wire)..might be an overkill though.

Kinda difficult to check the metal line while still in place. Hope the hollow screws don't break. The part number - just google 1152000058 co.uk . MB wanted an arm and a leg for the stupid line alone. And yeah,check the new line too for blockage :-)

Who knows what made the guy put the rubber in the housing...people get extraordinarily creative at times :D .Or very cheap...

Water Jacket
 

Well ;

It's certainly clean now ! .

I'm still getting reddish crud in my coolant, maybe I should use a stronger citric acid solution .

You're on the road to wellness, remember : this needs doing periodically, not just by miles .

My 60 year old mechanic swears that the lack of any orange/ reddish crud in my cooling system is because the previous owner kept a strong mix of G48 (Blue) coolant (glysantin) in the cooling system.

In his words "In the ol' days, 'em cars only had one colour other than tap water..Blue...and it worked really well"

Coolant Color
 

...That's interesting .

I'm past 60 Y.O. and have never seen blue coolant .

Maybe it's an up market thing .

Green and yellow yes, blue, never .

Coolant Color

In 1987 I got a '50 Chevy that was my wife's grandfather's. He died in 1953 and the car sat untouched in the garage for 34 years. I figured the block would be cracked from freezing (alcohol antifreeze). Pulled the dipstick and oil level was full & clean.

That's when I noticed a paper tag on the radiator "Prestone Permanent Antifreeze" installed 1953. It was blue and still good!
Prestone was originally blue!

To keep this Mercedes related I'll mention in the '70's when I was 16 my parents would not loan me $300 to buy a cherry '53 W187 coupe, "too old" they said. I still think about that car...

Interesting you say that. My W115 sat in a garage for 10 years with the glysantin coolant. Not a spec of rust!

Cruddy Coolant
 

You guys are lucky ~ I'm still finding opaque stuff in my distilled water.....

It's lighter colored now though, orange instead or red so maybe I'm getting there .

Good thing I found .80 cent gallons of distilled water at wallymart .

Thought I'd circle back to this thread to share that the car is back, leak free and running at a constant steady temperature regardless of traffic or speed. Fan belt squeal is also gone, probably due to the new MB water pump.

We really went to town on preventative maintenance. The final list includes:

1) New MB short hose
2) New MB Water pump
3) New MB Thermostat
4) New MB Fan Belts
5) New Monark pencil glow plugs
6) New Monark injector nozzles (Rebuilt by Diesel Injector Guru Greazzer)
7) New OFV (from Diesel Injector Guru Greazzer)
8) New MB Oil Cooler Hoses (New Old Stock)
9) New fuel filters and hoses
10) Citric Acid flush then rebuilt Radiator and steam cleaned and painted oil cooler
11) Sanded down all pitting/ corrosion from aluminum housings

Interestingly and unexpectedly, the car's heating system has REALLY improved. Heats up very noticeably in <5 mins and get's really toasty in < 10 mins. And that's without the fan on!

Blue coolant is back in the system she's sealed up for another decade (hopefully!)

When Prestone said "Permanent Anti-Freeze", they really meant it!