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Premium Member
1999 500SL, 1988 SEC
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1,272 Posts
Well really it can only be a couple of things. One is oil based from the crankcase, which I highly doubt. Second would be something to do with antifreeze, which I tend to think. Third is some sort of additive to the coolant. I know antifreeze is either propylene or ethylene based. Most are ethylene. That cant get gooey but I have not seen it like that. If things are not overheating, for a while I would run straight water for a while to see what happens. I say that only since if you add antifreeze now you will loose it when you drain it again. I would however drain it before you need the heat transfer antifreeze provides when it gets colder out. Of course there is another, although slight, possibility something
in the system is dissolving into the coolant馃槩
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #42
Well really it can only be a couple of things. One is oil based from the crankcase, which I highly doubt. Second would be something to do with antifreeze, which I tend to think. Third is some sort of additive to the coolant. I know antifreeze is either propylene or ethylene based. Most are ethylene. That cant get gooey but I have not seen it like that. If things are not overheating, for a while I would run straight water for a while to see what happens. I say that only since if you add antifreeze now you will loose it when you drain it again. I would however drain it before you need the heat transfer antifreeze provides when it gets colder out. Of course there is another, although slight, possibility something
in the system is dissolving into the coolant馃槩
What kinds of things can dissolve into coolant? I鈥檝e not encountered anything like this before.

I estimate it鈥檚 over 90% water right now. I recently grew suspect of the Zerex G-05, even though I鈥檝e seen time and time again that it鈥檚 the recommended formula for our cars.

Also, does the overflow tank have a silica pouch in it like other German cars?
 

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1990 420 SEC
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337 Posts
Could it be that the radiator is blocked or has an insulating layer of whatever it is? The heat from engine is mostly transported to temp sensor by coolant. Also the coolant exiting engine is hot as temp gauge shows so heat is transferred to that ok. Is the lower hose hot too?
 

Outstanding Contributor
350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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3,245 Posts
So this contaminant was not present when I bought the car almost three years ago. It hasn鈥檛 been present for most of the time I鈥檝e owned the thing as well. This is a somewhat recent development that occurred during my ownership of the car.
Well, that really cuts down the list of possibilities...
What鈥榮 this about acetone?
Acetone will disolve most epoxies, paints, etc.
is that safe to run through the cooling system?
I don't know off the top of my head. I was just trying to ID the stuff, but, if, as you said, it happened since you aquired the car, then that should eliminate any sealers.

It stands to reason that if it happened on your watch then it must be something that's water soluble, but, since it isn't water soluble, well, you must be overlooking something.
 

Premium Member
1999 500SL, 1988 SEC
Joined
1,272 Posts
Could it be calcium or salt if you used hard water, or water that was softened by salt. If its hardened calcium not much touches that
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #46
Could it be that the radiator is blocked or has an insulating layer of whatever it is? The heat from engine is mostly transported to temp sensor by coolant. Also the coolant exiting engine is hot as temp gauge shows so heat is transferred to that ok. Is the lower hose hot too?
There's definitely visible crud in the radiator when I look into the coolant inlet. The plan is to replace that and the water pump this month, but I really want to clean the cooling system first so as to prevent the new parts from getting contaminated.

Well, that really cuts down the list of possibilities...
It does, which is why I'm so confused lol. I have only ever put Zerex, water, and MB citric acid flush into my engine before this mess took place.

Acetone will disolve most epoxies, paints, etc.
I do like using it for parts cleaning on occasion.

I don't know off the top of my head. I was just trying to ID the stuff, but, if, as you said, it happened since you aquired the car, then that should eliminate any sealers.
Right. So acetone is probably not a necessary chemical to consider using anyway.

It stands to reason that if it happened on your watch then it must be something that's water soluble, but, since it isn't water soluble, well, you must be overlooking something.
I must be. It's remarkable how mysterious and difficult this contaminant is, given that a cooling system is a fairly simple thing. There are only so many materials present, and unless I got a hose made of some weird and terrible kind of rubber, or a bad batch of Zerex, or some extremely hard water somehow, I can't imagine what this is. I'm considering sending a sample to Blackstone Labs or some such company, if they'd consider analyzing a coolant sample and/or a sample of the white solid from my cooling passages.

Could it be calcium or salt if you used hard water, or water that was softened by salt. If its hardened calcium not much touches that
Well that's a concerning thought. Has anyone on this forum ever encountered hardened calcium?
 

Outstanding Contributor
350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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Calcium dissolves easily in weak acid, like vinegar or citric acid. Try vinegar and acetone (separately) on one of your samples.

Can you elaborate on why you don't believe it could have been there when you bought the car?
 

Registered
1991 560SEL (M117.968)
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127 Posts
Discussion Starter #50
Pm me, I have a new water pump
PM鈥檈d!

Isn't it distilled water that is supposed to be used with coolant?
Yes, that鈥檚 convention. Mercedes-Benz have issued a document about cooling systems that states that municipal water supplies in the United States are all acceptable for use in cooling systems, provided the appropriate antifreeze is used.

Calcium dissolves easily in weak acid, like vinegar or citric acid. Try vinegar and acetone (separately) on one of your samples.

Can you elaborate on why you don't believe it could have been there when you bought the car?
I tried vinegar on the block when the car was apart. It didn鈥檛 seem to do much.

First thing I did when I bought the car was change the radiator and hoses. Looking inside the water pump, I saw nice bare aluminum.
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #51
Based on the discussion here, it鈥檚 looking like I鈥檒l have to run just gallons of distilled water with perhaps MB citric acid dissolved in it for a while, and also get a new radiator and water pump stat.

Hawaii is rapidly approaching tropical summer temps, and my commute involves two gnarly hill climbs both ways (I got up and over the same mountain range twice). So this needs prompt addressing.
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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So, the only things you've added to the cooling system are antifreeze, distilled water and a radiator? I guess you could contact the radiator manufacturer and ask them what they may have left in the radiator, and the antifreeze manufacturers and ask them if they have any ideas.
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #53
There鈥檚 been a development:
I ran the L-11 (formerly known as Eskimo) degreaser flush through the system, and then flushed it with distilled water.

The heater got more effective, with readings taken at the vents registering about 35掳 C.

The car ran much cooler as well. There was still white crap in my radiator inlet when I looked, despite the positive signs. This leads me to believe that my contaminant has an oil component and a mineral component.

Previously, the flushes I鈥檇 tried were intended to deal with mineral contamination only. Since there was apparently oil mixed in with the white crap, it was impervious to the other flushes.

the car ran cooler on the drive in to work today as well, which was just the best thing ever.

I will follow this up with MB citric acid, and I still intend to go for a new water pump and radiator. Probably also a good idea to do new hoses too; mine are new enough, but they鈥檝e been through a lot!

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After 40 minutes of freeway driving, including going up a mountain range in tropical morning weather.
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #54
Got a new radiator and new water pump today. Decided to dissect my old radiator. What I found inside was nothing short of horrifying. I am at once relieved that I had the good sense to replace this (3-year-old) Nissens unit with another Nissens, and extremely concerned that this chemical terror is still potentially at large in my cooling system.

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Maybe this is where all of the stuff from the block congregated after I hand-cleaned/rebuilt/flushed the system? I don鈥檛 know.

looking at these close-up shots, does anyone have any ideas as to what this could be?
 

Premium Member
1991 560 SEL
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97 Posts
Oh goodness, that is horrific! I have no real world experience with what that is, but it reminds me of the head gasket sealant product I saw SamCrac recently use on a junk Range Rover in one of his videos. Glad you replaced the radiator!

Sent from my moto x4 using Tapatalk
 

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1991 560SEL (M117.968)
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127 Posts
Discussion Starter #56
New water pump, new radiator, distilled water, and Zerex seem to have put this problem to bed! I did a midday shakedown run in the tropical heat, with some hill climbing, freeway driving, red lights, parking lots, etc. Basically, I went grocery shopping at a store on the other side of the eastern region of the island lol. I saw 79掳-83掳 no matter how I drove.

The car has never behaved like this, not even when I had just installed my previous radiator, when it was new.

So while that white crap remains a mystery, perhaps it can also remain a memory.

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