OM651 Mysterious Coolant Leak.

steve gooding

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So Ive had my car now for nearly 2 years, never had to top coolant except a few months back. On Tuesday I get the low coolant warning, so top it up again. But the warning appeared on the way home today, checked it when I got home and it had dropped again, quite a bit, about 1/4 way down the tank. I tried to have a good look to see if I could see anything, but no obvious pools of coolant, or can I smell it. I know about the dreaded fuel filter housing cracking and leaking, but I cannot see any coolant around that area.. thermostat housing looks ok, can’t see any obvious leaks by the water pump.
I’ll try and get underneath it tomorrow, see if I can spot anything. Anyone have any pointers as to where else to check?
It’s a 2012 C220 cdi....

Many thanks
Steve


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Blobcat

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Have you checked the oil? Any "Mayo" in the oil fill cap?
 

Kev555

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Coolant does circulate around the EGR cooler in my Vito, if your EGR is same setup, could there possibly be a chance if theres a leak in there it might find its way to cylinders and burn off as steam in exhaust? wild guess but when you haven't any visible leaks? Maybe leak drying off on outside of hot engine but you would smell the stink as you said you havent
 
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steve gooding

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Coolant does circulate around the EGR cooler in my Vito, if your EGR is same setup, could there possibly be a chance if theres a leak in there it might find its way to cylinders and burn off as steam in exhaust? wild guess but when you haven't any visible leaks? Maybe leak drying off on outside of hot engine but you would smell the stink as you said you havent

Thanks, I’ll have a look. But I guess if there’s no visible leaks, and it’s leaking on the inside the only way I’ll know is to take it off...
Can’t say I’ve seen any steam out the exhaust, only the usual on a cold morning...


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ajlsl600

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have you had the lower covers off ? water can collect in there and may be a while before you notice if leak is small .if nothing seen there top up to normal level and find a cooling press test kit, pump to press NOT exceeding design press(used to be on tank cap) see if that finds yr leak. if nothing seen eng cold repeat the test at normal opp temp with due attn to removing tank top while hot.
 
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steve gooding

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have you had the lower covers off ? water can collect in there and may be a while before you notice if leak is small .if nothing seen there top up to normal level and find a cooling press test kit, pump to press NOT exceeding design press(used to be on tank cap) see if that finds yr leak. if nothing seen eng cold repeat the test at normal opp temp with due attn to removing tank top while hot.

Thanks. Not been underneath the car yet, but I’ll have a look tomorrow if I get a chance in between showers
If I can’t see anything I’ll just top it up and see how it goes.
It may one of those problems that needs to get worse before it can be properly diagnosed.


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Uncle Benz

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In my experience with these they usually leak when hot, and the residual heat in the bay dries the water off pretty quickly. What you’ll usually see is a white crust with a hint of green to it where the residue has dried up. Filter housing and water pump most common by far
 
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steve gooding

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I’ve managed to find a diagram of the entire cooling system, so will try to trace the leak tomorrow.
Thanks for replies guys


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Dean Fletcher

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I had the same on my e class om651 it was a tiny crack in the water pump housing barely noticeable and would only leak when up to temp. New water pump from Grangemouth I thing was around 116 quid. Very cheap.
 

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Water pump,
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Thermostat housing
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And finally heater matrix.
We have seen leaks from all of the above. :(
 

ajlsl600

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Thanks. Not been underneath the car yet, but I’ll have a look tomorrow if I get a chance in between showers
If I can’t see anything I’ll just top it up and see how it goes.
It may one of those problems that needs to get worse before it can be properly diagnosed.


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so long as it dont suddenly get worse halfway down the motorway ! not sure about the most modern temp guages but previously low/zero showing on guage dont always mean lo temp ,can mean no water to indicate reading ?? be alert.
 
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steve gooding

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so long as it dont suddenly get worse halfway down the motorway ! not sure about the most modern temp guages but previously low/zero showing on guage dont always mean lo temp ,can mean no water to indicate reading ?? be alert.

Thanks for the heads up... However.....
I think I may have been left with ‘egg on my face’. Go to top up coolant this morning (it hadn’t actually dropped as much as I thought), and the tank cap wasn’t tight
Would explain why I couldn’t find a leak
Have tightened it properly this time, but will keep an eye on it.
Thanks for replies guys


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Dean Fletcher

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Thanks for the heads up... However.....
I think I may have been left with ‘egg on my face’. Go to top up coolant this morning (it hadn’t actually dropped as much as I thought), and the tank cap wasn’t tight
Would explain why I couldn’t find a leak
Have tightened it properly this time, but will keep an eye on it.
Thanks for replies guys


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Fingers crossed matey
 

ajlsl600

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always good to discover a simple solution.....
 

ajlsl600

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clk3202001,sl6002003 with everything regrettably sold ,A class 170cdi auto. NG/TF1800 ML250
I had the same on my e class om651 it was a tiny crack in the water pump housing barely noticeable and would only leak when up to temp. New water pump from Grangemouth I thing was around 116 quid. Very cheap.

unless thats a fairly complex pump £116 dont seem that cheap to me.. £29.95 for my NG tf 1800 seems far more like it.
 
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steve gooding

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always good to discover a simple solution.....

No such luck, just been out to the boys footy match and back, and the level has definitely dropped.
I’ve had another look and I think I could see it a little wet just below the water pump. I need to get that belt cover off for a closer look but could well be the water pump..


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ajlsl600

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clk3202001,sl6002003 with everything regrettably sold ,A class 170cdi auto. NG/TF1800 ML250
No such luck, just been out to the boys footy match and back, and the level has definitely dropped.
I’ve had another look and I think I could see it a little wet just below the water pump. I need to get that belt cover off for a closer look but could well be the water pump..


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sadly,that does not seen unusual on this engine
 

ajlsl600

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clk3202001,sl6002003 with everything regrettably sold ,A class 170cdi auto. NG/TF1800 ML250
No such luck, just been out to the boys footy match and back, and the level has definitely dropped.
I’ve had another look and I think I could see it a little wet just below the water pump. I need to get that belt cover off for a closer look but could well be the water pump..


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sadly,that does not seen unusual on this engine
 


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