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1986 SEC 560
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164 Posts
Discussion Starter #1
Hi All,

Hes the thing my 560's collant light came on and I added coolant. 2 days later, empty again. Not a drip under the car , no wet hoses nothing not even under pressure and running conditions. Brought it in, my guy is stumped. Its not in the oil pan, its not leaking into the washer fluid tank (heated fluid) its not leaking out of anywhere and I notice no performance change, exhaust gas change, rpm change or anything else abnormal. WHERE THE HELL IS IT GOING!!?

any help will be much appreciated.

Thanks,

- Dan
 

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1998 S500
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90 Posts
Also check that the radiator is not leaking. I've had it leak slow enough that it would just evaporate on the hot radiator. It did leave a green stain, though.
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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7,035 Posts
I'd say water pump too..

I'd say a good underside check of the water pump... a mechanic might see "seepage" marks and assume they are OK because they look "old" and some pump seepage is normal for 100K..., but the aluminum block runs hot and recent added seepage would not necessarily show like freah/wet....

Water pumps show very little advance signs of failure, but coolant loss is a real good clue... the pump increases seepage...then will either show coolant loss, slight added temp gain... then blewey... a 10oK plus would seem about spot on from my past experience...

You're worried about head gasket seepage - but water pump failure is a lot-lot more common....

A Lot of OE style water pumps out there, India not good, Spain OK-so so, Italy OK so-so, then German...
 

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Mercedes 420 SEL
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617 Posts
1. Check/ replace radiator cap.

2.) Check oil, is it frothy, milk chocolate color, etc.

3.) Check water pump ( as mentioned above).

4.) Check carpet interior for dampness (passenger side)...again, as mentioned above.

5.) I don't know if possible, haven't tried it, but can you put a tracer dye in the coolant (like they do with air conditioners?)

6.) Re-check overflow and hoses to and from overflow.

Good luck with it. Lots of good advice mentioned above.

My guess is going to be radiator cap or water pump.
 

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1985 500 SEC, 2005 E320
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1,294 Posts
my money is on the heater core. one of the few places it can leak without leaving puddles on the ground. at least, at first. it will eventually.
With the amount claimed, he lost in a short time, that sorta negates the water pump and radiator. Otherwise, you'd see puddles which he's not seeing. Therefore, the heater core is the only logical conclusion based on the info given. Good luck. Let me know if I win the bet.
 

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'86 E300 Diesel '82 300 SD '87 560 SEL
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432 Posts
DarkOneSK said:
my money is on the heater core. one of the few places it can leak without leaving puddles on the ground. at least, at first. it will eventually.
With the amount claimed, he lost in a short time, that sorta negates the water pump and radiator. Otherwise, you'd see puddles which he's not seeing. Therefore, the heater core is the only logical conclusion based on the info given. Good luck. Let me know if I win the bet.

Sorry, man! I called it, allready!:)
But, I hope I'm wrong...
 

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1984 500 SEL euro, 1989 560 SEL, 1980 450 SL, 1981 DeLorean, 2013 F10 BMW
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1,253 Posts
Are you not smelling the "sweet" smell of antifreeze? Pressure test the system and take a wiff after a drive to tell if it is burning off the motor.

Check the hoses to see if any buldges or swelling is noticed. The hoses can leak from the inner cores as well.

Regards,
 

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1986 SEC 560
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164 Posts
Discussion Starter #11
Update

Just got he car back from my mechanic, he is as perplexed as I am:

1. The carpet on the passenger side is bone dry
2. the water pump is not seeping
3. the oil is nice and black and was changed, no milky residue, no frothiness
4. No green stains or "sweet" smell underhood or in exhaust fumes
5. No bulging hoses
6. no leakage near head/block or near valve cover.

So here's where I'm at. The light comes on after a few minutews of driving every time, the tank refills itself immediately after the car is shut off, although a little less every time, the compartment with the senor fills up the slowest and last. I happens quicker when at idle rather than cruising around (stoplights and such). It was recommended that I switch the radiator cap to a 7 lb unit instead of the high pressure stock MB one. Any othetr ideas or things I'm overlooking?
 

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Depends on the day!
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13,337 Posts
I'd bring it to my guy Peter in Mineola.

Did your guy pressure test the system? Best way to find the leak is to crank up the pressure to 1 bar and look everywhere.

Worst case it's a head/intake manifold leak and it's collecting in the valley under the CIS plenum then cooking/blowing out while you drive.

Jonathan
 

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86 560sec-168K -Ext. Light Ivory/Int. Black/01 E320 4Matic Wagon Brl Silver/Black/ Mad '95 Q45
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852 Posts
jhodg5ck said:
I'd bring it to my guy Peter in Mineola.

Did your guy pressure test the system? Best way to find the leak is to crank up the pressure to 1 bar and look everywhere.

Worst case it's a head/intake manifold leak and it's collecting in the valley under the CIS plenum then cooking/blowing out while you drive.

Jonathan
Is peter a MB Guru - i live 40min from Mineola - Please post info:bowdown:
 

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Depends on the day!
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Yes he is very much, shoot me an email...I don't put his info out there as I think he basically runs @ capacity as it is.

[email protected]

Jonathan
 

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1986 SEC 560
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164 Posts
Discussion Starter #15
I changed the pressure cap to a lighter 7lb one. It seemed to help a little, the level still dropped by not as much as usual. It just seems like no fluid is returning to the tank and being cycled through the system. It returns once the engine is shut off. I just don't get it.

I did smell it burning today and the exhaust smoke was slightly white but only on initial startup while idling, it went away and being driven for a little bit
 
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