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  #1  
Old 09-09-2017, 02:33 PM
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W124 mystery coolant leak

Hi folks,

Since the head replacement there has been a small coolant leak which eludes me, the obvious sources given the work have been checked and ruled out.

Both under trays have been removed as the drips appear at the bottom of each wing (fender) towards the front, my thoughts were heater core but can find no trace of water inside the cabin anywhere - on some models there is ab expansion tank inside one of the fenders, not sure if mine has this but no visible pipe work heading in there.

All engine bay pipework is good, no leaks, new water pump and thermostat also fitted same time as head but again, no leaks easy to see too.

I do have an endoscope but not sure where to start, any tips?

Cheers

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-09-2017, 03:05 PM
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The easiest option maybe to remove the fender liner and have a look, might also give an access point for endoscope.
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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-09-2017, 03:14 PM
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On US cars a hose from the pressure cap fitting disappears into the fender/wing to an overflow bottle. I think it can overflow further to the ground. If your pressure cap fitting has such a hose, temporarily route it to a bottle in the engine bay to see if it fills during everyday driving. More scientifically, get a cooling system pressure tester to find the leak. Or the ou might have a creative way to pump the cooling system to 1.6 bar.

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98 E320s sedan and wagon
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Old 09-09-2017, 03:26 PM
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Cheers sixto, will take a look tomorrow to see if tank is fitted - the system is not pressurizing so i do suspect a leak somewhere, just can't place where it might be given the pipe routing.

Forgot to mention, no a/c fitted.

Ref thread for research:

300SDL leaking cooling from expansion tank

Courtesy of above thread, wonder if this is it?

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-09-2017, 03:36 PM
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https://www.harborfreight.com/radiator-pressure-tester-kit-63862.html

I have this one. It works fine but I haven't had issues others posted. Mine has been working for a couple of years but I don't test every day. It does come in a carrying case.
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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. Probably up for sale in the fall 2020 still have it. 85TD beginning to repair to DD status. Waiting on shop to do minor but more than I can do rust.
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Old 09-09-2017, 08:31 PM
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How about where the hose to the heater core connects to the cylinder head?

Sixto
98 E320s sedan and wagon
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Old 09-10-2017, 12:13 AM
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The Bottle filled with Green-ish Coolant

in your picture is the overflow.

(Bonus locator is the Vacuum Storage Canister
[Twin Black Plastico Balls , Joined at the Equators] )

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'Going with Sixto's suggestion...
If the Heater Core to Block connection is like the Earlier OM60X.XXX
engines (Which uses an O-ring fitting secured by a Circlip type device)
It COULD be slowly leaking THERE and being evap-ed by engine Heat ?

('As I've admitted Earlier, here, I can sure "Prevaricate Up" some
Wunnerful potential explanations for the Unknown.)
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Old 09-10-2017, 07:44 AM
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Quote:
Originally Posted by sixto View Post
How about where the hose to the heater core connects to the cylinder head?

Sixto
98 E320s sedan and wagon
First place I looked as O ring used was for something else, usual parts guy was away so popped that on just to get going - no sign of leak from that side (washer bottle now removed, RHD car)

Compress, cant see any pipes going into the fender, the overflow on mine is basic clear tube hanging on inner side.

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-10-2017, 07:52 AM
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I lifted the drivers carpet (RHD), there's a very small amount of water there but this could be normal car usage with heavy rains here, nothing in passenger well at all.

Removed instrument binnacle, as usual not much help as everything is so tightly wedge in can't get my hand in - waiting for lap top battery to charge, will have a poke around with endoscope when done.

Although I can see one pipe coming out of the duo valve disappearing into bulk head, there appears to be two more tightly wrapped underneath - got a feeling it's one of these - any idea what they do, also appear on other side of bay exiting?

Main pipe with two smaller underneath



Pipe exiting otherside of engine bat, lower of two

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-10-2017, 08:05 AM
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Found a diagram courtesy of bayhas.com - thanks

There are two cold pipes (in blue) exiting the heater core, top right looks as though it has to travel across the inside of bulk head to terminate in A31y2

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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Old 09-10-2017, 09:09 AM
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Thinking out aloud, if I isolate those three pipes with hose clamps it should in theory cut of da leak?
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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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  #12  
Old 09-10-2017, 12:09 PM
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Jeremy noted a defect in the LHD '95 E300 monovalve or at least factory replacements. The plastic case cracks and leaks. Maybe the same defect found it's way to RHD duovalves. It's strange that the diagram doesn't show an auxiliary pump between the duovalve and the thermostat housing. I see a branch from the heater supply line to the windshield/windscreen washer bottle. The coils in the bottle are known to leak causing coolant to overfill the bottle.

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98 E320s sedan and wagon
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Old 09-10-2017, 12:21 PM
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Yep, I read that also and had a good look this afternoon, slight error on my part as the pipe which i clamped was the on eon right of picture, A31y1, however this made no difference at all, drip, drip and more drips..

Reached in to the two alloy pipes behind binnicle, both dry so not tracking down, it has to be where those two pipes meet the rubber coming from under the duo valve - my set-up looks slightly different to the diagram (doesn't have heated washer tank) .

Tried to get some pics of the connections but cannot see any after several searches, probably need to go in from the foot well - do you know which side of the fir wall the joins are?


edit: two alloy pipes



Thanks,
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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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  #14  
Old 09-10-2017, 03:11 PM
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Checked on EPC, hoping it's one (or both) of the connections between 35/6 at bulk head or fire wall.

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1996 Mercedes S124 E300TD - 129k - rolling restoration project -

1998 Mercedes W210 300TD - 118k (assimilated into above vehicle)
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  #15  
Old 09-10-2017, 03:15 PM
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Ah, so there is an auxiliary pump.

Sixto
98 E320s sedan and wagon

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