Mercedes ML270 - possible broken crankshaft question

[LostKiwi]

A turbocharger has nothing to do with any chains other than sharing oil for lubrication.
I struggle to see how a seized turbo can damage the timing chain.
I can see that loss of lubricant or oil pressure can cause a seized turbo or seize camshafts destroying the chain etc and yes that would cause massive damage. If it were the turbo oil feed line that failed then perhaps that set the chain of events in motion but that's not the turbo itself being the cause.
I guess diesel runaway could have been the cause where if the oil seal on the inlet side of the turbo failed the engine will run uncontrollably on the engine oil, however that would be very obvious to any person driving it!
The only thing that makes any sense at all is oil starvation. Low oil level, major oil leak or oil pump failure.

 

[Blobcat]

My thanks for the continued ideas and advice all!

Based on the reports here we did have the car moved to another garage, however whilst their inspection has yielded a more detailed understanding, its sounding like its still a write off. They've reported that there's a fully seized up turbocharger which they think might have caused damage the chain which then damaged the rest of the engine to the point where it no longer holds compression. From their view the engine is very likely dead and a replacement, plus fitting, would be far more than the car is worth

My father has been wondering if the car had had the gear stick moved whilst it was being driven which resulted in it being over-revved and thus setting things up for things to get broken.

In neutral or Park Mercedes won't over rev, they limit to ~4,000 in N or P

 

[robin.large]

The respective garages just reaffirm my overall suspicion of so called commercial garages. Not all - but sufficient that I shall continue to avoid them all.
A sized turbo, as said, is a result of some failure, not a cause.
What caused it to sieze? Almost certainly oil failure either seal on turbo ( but you'd see the smoke for miles), oil pump failure, but you'd get an oil pressure warning and nothing reported on that.
I'm just not feeling the full story here.

So.... water pump failure or loss of coolant. More difficult to spot and would light up warning but...initially less catastrophic until if course the engine cooks, partial or full seizure which rips the rings off, jumps or breaks timing chain, plus at this point everything would be so hot that the turbo would weld itself up as the whole lot shut down.

I just love a who/what dunnit!

End result is the same. Skip.

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[oigle]

Seized turbo would have nothing to do with your issues. A broken chain would has caused large amounts of damage and created the scene you have described. Bent valves, damaged pistons etc etc. Yep, probably a writeoff.
Overrevving would be unlikely. Diesels don't rev fast enough to hurt themselves. Chains do break - not often but they can.

Ian.

 

[DREAMER NO2]

Yes but if the valves were damaged [bent] i dont think the engine would turn over to get a compresion reading it would not turn over .Someone explain to me if thats wrong

 

[LostKiwi]

Yes but if the valves were damaged [bent] i dont think the engine would turn over to get a compresion reading it would not turn over .Someone explain to me if thats wrong

If the valves are bent out of the way it will turn.

 

[DREAMER NO2]

LostKiwi i also had a crank go on a 1965 Sunbeam Rapier with a Holbay engine .It broke just after the main bearing on 4 cylinder .Engine would run but no drive , it was just stationery I wasted that engine my self .It would refuse to start. But it had seen better days oil leaking out every place you could think of, and when it did start i just put my foot on it to the floor,, i over did it i .And ha ha i just had this bang and then no drive . After that i fitted an Hillman Super Minx 1600 engine in , and married it up to the overdrive .She was a dream to drive once sorted out .

 

[ernieh]

LostKiwi i also had a crank go on a 1965 Sunbeam Rapier with a Holbay engine .It broke just after the main bearing on 4 cylinder .Engine would run but no drive , it was just stationery I wasted that engine my self .It would refuse to start. But it had seen better days oil leaking out every place you could think of, and when it did start i just put my foot on it to the floor,, i over did it i .And ha ha i just had this bang and then no drive . After that i fitted an Hillman Super Minx 1600 engine in , and married it up to the overdrive .She was a dream to drive once sorted out .

One Sunday night in the early 70s, my FIL, in his 60s, broke a crank in his Anglia 1200 Super. He never drove above 40 but had a problem with clutch control. Hence I think it probably saw some over-revving in its day.

Nice and simple engine change in these days...

Ernie

 

[oigle]

Yes but if the valves were damaged [bent] i dont think the engine would turn over to get a compresion reading it would not turn over .Someone explain to me if thats wrong

OP said tested and got NO compression readings. Who says motor even turned over? "tested" could mean anything.

 

[DREAMER NO2]

oigle your right its was i was getting at .

 

[stumo]

The only way you can overrev these is on overrun down a long steep hill. The trans wont downshift if it would exceed redline, and the engine torque drops like a stone at 4000rpm, and fuel cuts at 4400rpm. So thats not the cause.

There is no oil pressure warning on om612, only oil level. So it could have lost oil pressure. That would explain the turbo siezing.

I dont trust your drivers version of events. There would have been a hell of a racket.

Both garages are rubbish at diagnosis. But it seems the engine has self destructed internally. You xould maybe get a wrecker engine swap. The om612 is pretty bulletproof when maintained properly. Mine are still running strong at 300k and 450k.

 

[robin.large]

I'd still go for loss of coolant over loss of oil. But it's one of the two I'm sure. It would be a quieter end to the engine

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[DREAMER NO2]

Will we ever find out just what the problem was in the end .

 

[Overread]

Sadly pulling everything apart to find out the exact cause and then likely having to replace the engine or major works - its just not economical to attempt. By the time we'd be finished we'd have spent more than an equivalent car would cost to replace it. We aren't happy, but at this stage we've not really got another option and don't want to throw more money down the drain than we already have.

 

[DREAMER NO2]

Did you think about just replacing the engine .If the car is nice and in good condition it is worth thinking about it.

 

[Overread]

Aye we considered it, but by the time we've paid for a new engine and the man hours for it to be fitted we'd be more than half way to the cost of replacing the car for a like condition "new secondhand" working car. Plus that might only resolve the engine issue, we've no idea if there might be other damage or other issues that could rear their heads soon after - not to mention the trick of finding a good quality secondhand engine with no issues of its own.

 

[DREAMER NO2]

Overread So you going to cut and run . May be someone would be interested in it on the forum .But if you get one the same keep it for parts in the future .

 

[ajlsl600]

That what i did with my A class bought another for £100 ran it for three months to understand any issues,then broke it and racked all the parts,been well worth it...