Engine Failure on Mercedes C220 2.1l diesel OM651

stringer

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Hiya i am a new bee? i am after some technical help. i have a 2012 c220 2.1diesel om651 witch had an engine fault i removed the engine and striped it down no inspection found the big end bearings seized to the crankshaft so the engine was sent to my local machine shop were they polished the cranck shaft supplied all new standard bearings new fal oil pump cleaned the pistons and fitted new rings and small end bearings they all so put the engine block and other engine parts through there hot wash machine so when i got the parts back every thing was nice and clean for reassembled i made sure all oil ways were clear and proceeded with the rebuild every thing went back nice with no problem all new gaskets and seals and all so replaced the hydraulic directional valve as well i refitted the engine with no problems and cranked the engine to build up oil pressure before the start up so the car started up fine and sounded fine after all the checks done i.e. levels and made sure the fan comes on i booked it in for the mot all good so far its only when i was on my way back home in traffic the engine developed a knocking noises i was stuck in traffic i got the car round the corner and had it recovered home i then drained the oil and there was what looks like debris from the bearings so again i remover and striped the engine and found the big end bearings have worn out worse then before i spoke to the machine shop and dropped all the engine parts to them to check out they sent the oil pump away for test and come back all ok they all so went through the engine to try and find what caused the engine to fail but with no joy as every thing seams ok they say so i am in a fix were the cranck is scrap and two rods all so scrap but i would like to find out if anyone else has had a problem with oil pressure on these engines tsk
 

alexanderfoti

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Did you measure the oil pressure at all after the rebuild?

You could have swart and bits of metal blocking the oil cooler which would give very reduced flow.
 

umblecumbuz

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... and how rigorously were the crank journals measured before reassembly?
 

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Did you fit new con rods, the big end could have been oval. ? simetimes it’s easier and more cost effective to fit another engine, especially if you didn’t know the cause of the engine failure.
 

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It's also crucial the big end caps don't get fitted to any other rod other than the one came from and even they must be fitted same way round.
 

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It's also crucial the big end caps don't get fitted to any other rod other than the one came from and even they must be fitted same way round.

we used to mark the caps with a centre dab 1-4 etc.
 
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stringer

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we used to mark the caps with a centre dab 1-4 etc.
Did you measure the oil pressure at all after the rebuild?

You could have swart and bits of metal blocking the oil cooler which would give very reduced flow.
Hi mate tks for the reply the oil cooler was cleaned & no I didn’t check the oil pressure after the rebuild
 
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stringer

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Did you fit new con rods, the big end could have been oval. ? simetimes it’s easier and more cost effective to fit another engine, especially if you didn’t know the cause of the engine failure.
No con rods fitted as the bearings were not worn out it was semi seized on the the bearing to the Cranck
 
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stringer

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... and how rigorously were the crank journals measured before reassembly?
All the journals were measured by the machine shop and polished the cranck
 
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Problem with this engine is oil cooler, coolant passages in it are very small and get clogged. Because of this the cooling of oil is reduced. Oil becomes too thin to lubricate and this is the reason for bearing failure. Get a new cooler and oil pump and you are golden for a long time,
 

ajlsl600

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This why I never allow a start till oil light out and pressure seen on manual guage
However I think there is a build error here. Something like a bearing span shortly after start.or an oilway plugged after start. Sad story. I prob spend three days looking at bits before I assemble an eng or tranny. And I use the folded newspaper method of checking bearing clearances 40 yr.no failure. Hope you locate cause .always doubts if u dont see cause .good luck
 
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In my experience bearings that have not yet been broken in create extra heat and with no oil coolers and 2 turbos it is more than enough for bearings to seize. Have seen a car with third engine om651, first 2 had spun rod bearings with old oil cooler.( They inspected the oil cooler by blowing air through and the costomer was told it was fine) but as it came out the cooler wasnt effective enough to cool the oil) with new cooler it has done 50k km and the engine is fine.
 

Uncle Benz

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Many many years ago I got caught with one like this. Turned out to be a crack in the engine block across an oil way, therefore losing oil pressure through the crack. I learned a lesson from that. Never rely on a rebuild unless you have established the reason for the original failure and resolved it. I'm sorry for the topic poster, but unless you can positively identify the reason for the failure don't waste time and money doing it again.
 

ajlsl600

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In my experience bearings that have not yet been broken in create extra heat and with no oil coolers and 2 turbos it is more than enough for bearings to seize. Have seen a car with third engine om651, first 2 had spun rod bearings with old oil cooler.( They inspected the oil cooler by blowing air through and the costomer was told it was fine) but as it came out the cooler wasnt effective enough to cool the
oil) with new cooler it has done 50k km and the engine is fine.

Useful info that.. stored for future ref.
 

Gazwould

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Not to mention a dpf regeneration sees diesel fuel stripping the lubrication from cylinder liners and entering the engine oil to have fun with .
 

ajlsl600

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You can use diesel as eng oil.I have spent yrs startin new builds on 50/50 eng oil n diesel.I start em see oil press run for a min or two.max Drain, open filter look rubbish .no issues new filter fill 100% oil. Away u go.
I have found it beneficial to take option to flush system after a build ,especially one I have had limited involvement in building , remember near all high press fuel pumps are lubed by the fuel passing thru it. I never had an issue doing this
Not advising anyone to do this , but statement above accurate for me
 
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