Mercedes E200 OM651.925 Coolant Leak Problem

[VicNorth]

Hi all,

I am new here and this is my first post in this forum after trying to find any info on the internet about om651 engines having a coolant leak problem but nothing matches my one.

I own 62 reg prefacelift E200 CDI (om651.925 variant engine) and had to add some coolant in the past, maybe couple of times over a year and a half and very small quantities so I thought it's fine abd may be the cause of evaporation. Recently, which was two days ago, add coolant message came on, so I opened the bonnet and saw that coolant is quite low level (less than a quarter of expansion vessel) so I added to normal again, that's really strange I thought but maybe it evaporated a lot driving in such hot weather over past few weeks here in UK. Biggest surprise was yesterday when I started my car after work and got same 'add coolant' message again, hence I only covered 35 miles in early morning, the level was at bottom of vessel again, topped up. After driving less than ten miles same message, stopped at nearest petrol station, topped up and finished last coolant I had in my boot. Drove off and a after few miles same, stopped again, checked, there's still some coolant left on bottom, barely made back home... While driving engine coolant temperature didn't go above (on the dash) even getting through bit of traffic. Put car into garage to see if I can find any leaks, engine off, first checked around pump and hoses, radiator, seems all fine, when suddenly noticed unusual sound coming from inlet manifold area. Here it is, leak is located, lots of liquid above intake manifold and spilled around it and down the side of engine, puddle under car too. Can't see precisely where coolant is coming from, view is very limited by loom harness and hoses, but definitely above air inlet in between thermostat and fuel filter. Would anyone have a auggestion what may have failed in there? Seem just bellow the glow plugs level... Can it be a head gasket?

Also noticed steam coming from oil filler hole while engine is hot when switched off and cap open. Some thin layer of brown residue/sludge on overhead crankshaft couth my attention as well, knuckles themselves are clean where have contact with tappets. Is this normal to see on 105k mile engine?

Checked engine oil level and looked for anything suspicious secerse times over last few days, everything seems ok, no milky stuff, dark brown oil almost black in colour, although had car cerviced 1.5k miles ago.

Any comments on this please?

Cheers. Vic

 

[Uncle Benz]

You definitely have the common leak from the plastic coolant pipe that includes the fuel filter holder. It leaks where it bolts to the cylinder head. Mercedes have modified the part to a three bolt fixing instead of the two, which are common for leaking. Worryingly though, it sounds like you might have water in the oil now, which might mean you have blown the head gasket. I think you need to seek professional assistance. It's your use of the word "sludge" that concerns me. Some brown, dry staining of the non contact parts of the camshaft is fine, but sludge sounds ominous to me.

 

[VicNorth]

You definitely have the common leak from the plastic coolant pipe that includes the fuel filter holder. It leaks where it bolts to the cylinder head. Mercedes have modified the part to a three bolt fixing instead of the two, which are common for leaking. Worryingly though, it sounds like you might have water in the oil now, which might mean you have blown the head gasket. I think you need to seek professional assistance. It's your use of the word "sludge" that concerns me. Some brown, dry staining of the non contact parts of the camshaft is fine, but sludge sounds ominous to me.

Uncle Benz: thanks for your response, that's very helpful, at least I now know what may be the cause of coolant leaking so badly next to fuel filter and all over top of intake manifold.

Like I mentioned earlier, that brown substance on non contact part of camshaft is very thin layer of what might truly just be a residue of oil or fuel additives settled there from blowby as I can't see any butter like formations on bottom of oil filler cap or around camshaft nor in the oil, just dark brown almost black engine oil. This so called residue when swiped with finger comes off easily leaving shiny camshaft metal. However, there's no sign of it on the aluminium camshafts casing walls or bottom where I can see. That's very strange in my view. And yet, how to explain light steam coming out of oil filler hole while engine is hot, but not running? I don't remember that happening last time I had the cap off in such instance, which isn't that long ago, maybe less than a week back. If I only could remember had the camshaft that pale brown residue on it... I'm coming to a thought that if that steam actually is the water content evaporating from coolant in the oil, so is it possible that what I call residue actually is a layer of rust forming on nonncontact parts of a camshafts? As residue would settle on any type of material, where rust is more specific to iron or steel containing iron, because all aluminium is bright and free from any residue apart some dark oil at bottom around tappets/lifters.

Still hoping for a smaller failure of Uncle Benz's mentioned part, as it really comes very close to what I found so far, back home now, back to my garage, will check everything again, engine cold this time as didn't even think going to work by own car, got a lift instead until I get it sorted.

Can post some photos or videos as well if that's would be of any interest.

P.S. Is there a file size limit to upload a file here?

 

[VicNorth]

And I'm sorry for a word "sludge", I think I've picked a wrong term, nothing that awful what I discovered so far and described above, at least not yet.

 

[Uncle Benz]

I think you'll probably be ok with just swapping the coolant outlet. I have replaced quite literally hundreds of these coolant outlets, and not done a single head gasket replacement yet!

 

[VicNorth]

Here's how the oil looks:



And so called residue on camshaft, it can actually be seen where I swiped a finger couple of times:



Does everything look ok?

 

[Uncle Benz]

Just change the coolant outlet pipe, I think you'll be fine.

 

[VicNorth]

So I got under the bonnet this evening again to check if I can see part number of that coolant outlet, took fuel filter out from its position, looked in there - nope, undone some hoses to have a better view of what I'm dealing with, looked around everywhere and found it at the back of fuel filter housing. Part number for coolant (water) outlet - fuel filter housing is A6512001056. Searched for it online and came up with some results, plenty of used ones but skipped those right away and only ones matching this OE number are aftermarket parts, same look, same two bolts to cylinder head... Then came across a suggested OEM part number A6512003900 which is exactly what Uncle Benz mentioned earlier, original part, comes with all bolts included, three holes for bolts to go into cylinder head, straight from MB dealers on eBay for mere £30-35, sweet. Only thing that my engine's head has only two holes for them three bolts but they claim that this part fits ALL OM651 engines.

Presumably one hole will not get used and other two are aligned exactly same as on a superseeded part which on my engine. Probably later variants of this engine incorporate that extra hole for a third bolt until OM651 got/gets replaced by OM654. I might be wrong, don't know much of MB engines history.

Back to the point, got couple of questions: should I go for an upgraded three hole part (A6512003900) with no worries it wouldn't fit and what size star socket I need (Exx?) to be able to take it out and fix new one in? Also, do I need a precise torque on these, especially ones which go into cylinder head? If so, how much of torque?

Thanks for letting me know in advance!

Below here's a photo of an area of my leak problem:



And one more:



Want to take it out tomorrow, just need to get that star socket to fit my socket set.

Will post an update how it goes!

Cheers

 

[mrmb]

Hey. Did you manage to change the housing? Did it take you long to do it?

 

[VicNorth]

Hey. Did you manage to change the housing? Did it take you long to do it?

Hi mrmb, should get it delivered today along with 1/4" drive deep star socket set (recon it's E8 or E10 size). Will post again as soon as I'll get on in. Vic

 

[Uncle Benz]

Are you sure you don't have the third hole ready to go on your cylinder head? 2013, I'd expect it to be there, just not used at present.

 

[VicNorth]

Are you sure you don't have the third hole ready to go on your cylinder head? 2013, I'd expect it to be there, just not used at present.

Surely no third hole in cylinder head (end 2012 manufacture, 2013 reg, pre-facelift model). Took that bastard out this evening and you were absolutely right about the fault.



It can be seen clearly that bottom of the outlet has some damage and seal is deformed, too. Damaged plastic is actually a chipped away inner flange of the seal bed. Half of the chipping was still there when I took it out, the other half, I'm concerned, has gone into the cooling system. I now think of draining whole coolant system prior filling it up again.

 

[mrmb]

Did you have to take out EGR cooling and drain the coolant or you have somehow manage without taking out EGR Cooler. I thought I had a small leak but after filling the system a bit I did not notice anymore that coolant was missing a bit. Water pump is fine, all hoses are fine, EGR cooler was clean is well so the only think I am thinking of is to check the fuel filter holder However when I have taken a look at my engine I do not think I will be able to take out this holder without removing the EGR cooler as there is not enough place to get to the 2 screw which is on the right side.

 

[VicNorth]

Did you have to take out EGR cooling and drain the coolant or you have somehow manage without taking out EGR Cooler. I thought I had a small leak but after filling the system a bit I did not notice anymore that coolant was missing a bit. Water pump is fine, all hoses are fine, EGR cooler was clean is well so the only think I am thinking of is to check the fuel filter holder However when I have taken a look at my engine I do not think I will be able to take out this holder without removing the EGR cooler as there is not enough place to get to the 2 screw which is on the right side.

Yes, EGR cooler has to be removed in order to be able to get out the coolant outlet and new EGR cooler gasket is included in coolant outlet package. I didn't drain the system yet as coolant level was just below this outlet as it leaked thru the bottom of it. However, even after draining cooling system completely there will still be coolant in EGR cooler due to placement of hoses (feed and return on the top of EGR cooler). V

 

[mrmb]

I have heard that coolant system on OM651 is a bit hard to bleed the air from. Do you think the standart method of just opening the cap and let the engine to warm up with High Cabin Temp set will do the trick?

 

[VicNorth]

I have heard that coolant system on OM651 is a bit hard to bleed the air from. Do you think the standart method of just opening the cap and let the engine to warm up with High Cabin Temp set will do the trick?

Personally I'm not aware of this, going to find out soon for sure.

 

[VicNorth]

As I've got EGR cooler out, would it be worth cleaning all the soot from it I wonder? And what cleaner would get rid of that soot best, is carburettor cleaner good enough for doing that? I have couple of cans of diesel intake cleaner sitting on the shelf as well.

 

[mrmb]

I think carburator cleaner will do a good job

 

[VicNorth]

That's exactly what I got on me way home, plus a 3in1 heavy duty foaming cleaner / degreaser.

 

[Steve@Avantgarde]

Personally I'm not aware of this, going to find out soon for sure.

They can air lock quite badly. Now I always fill them with the front end jacked up, seems to make a difference.