Mercedes ML270 - possible broken crankshaft question

[Overread]

Greetings, hope I can get an answer to this question regarding a Mercedes ML270 engine. The other day the car was being driven and whilst overtaking lost all power with the engine fully dead. I was not in the car at the time, but the driver reported that there was no loud banging or other loud sounds, simply an engine struggling sound for a moment and then totally dead.

We've had the car towed to a garage and they've reported that they tested is and didn't get any compression from the engine. They are suggesting that the issue is a broken crank shaft. However with no loud sounds reported and the rarity (I presume) of crank shafts breaking I'm wondering if there is anything else that might have happened which would be more affordable to repair and which would make it worth having the car inspected by another mechanic.

I've had some thoughts that it could be the timing chain being stretched/bent/damaged, but I wonder if there are any other issues (or common issues) that might cause a similar result and might give a false impression of the crankshaft being broken.

 

[joderest]

You might like to consider a snapped timing chain, the fact that there is no compression would indicate that at the very least valves are open when they should not be. The garage registered no compression and said crank shaft snapped, how did they spin the engine ?.

 

[LostKiwi]

Simplest way to check for broken crank is turn the engine over by hand and look for movement of the torque converter

 

[robin.large]

It's a very odd conclusion.

Surely they would say no compression on cylinders X,y, z.... But compression on cylinder a,b ,c.

If no compression on any cylinder then the crank isn't turning at all... Which would be pretty much unheard of... Unless hydrolocked through deep water?

I have personally blown 8 pistons on a supercharged V8. Which gave ' no compression' but that was an 800 bhp fuel issue!

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[joderest]

I suppose if engine turns on the starter and aux belt moving would confirm crankshaft in one bit.
You need more tests/information

 

[LostKiwi]

I suppose if engine turns on the starter and aux belt moving would confirm crankshaft in one bit.
You need more tests/information

Not necessarily. Depending how it's broken there can be drive between the broken sections. You need to check relative movement end to end. There should be zero.
This is the clutch mounting plate off a Smart. It was still able to drive the vehicle.

 

[Overread]

My thanks all, we were concerned at the mechanics initial report and we've decided to have it moved to another site for an assessment by a different firm since it sounds like its possible that its not the crankshaft.

Further my father is curious if there's an exploded diagram for the engine that one can access (either online or in book form). He used to work on cars many years ago and wants a better understanding of how the engine is put together and works so he can better understand what might/is/has happened.

 

[LostKiwi]

Probably best looking at the parts manual.
http://mb-teilekatalog.info/view_Gr...yp=M&catalog=21T&model=612966&spmno=0&group=0

Note this may not be exactly yours but is the same family.

The 270 engine is generally held to be a strong reliable lump with no real issues other than leaking injector seals.
They certainly aren't known for crankshaft failure or timing chain issues. If you had either of these you'd be very unlucky.

 

[Blobcat]

Probably best looking at the parts manual.
http://mb-teilekatalog.info/view_Gr...yp=M&catalog=21T&model=612966&spmno=0&group=0

Note this may not be exactly yours but is the same family.

The 270 engine is generally held to be a strong reliable lump with no real issues other than leaking injector seals.
They certainly aren't known for crankshaft failure or timing chain issues. If you had either of these you'd be very unlucky.

Lots of “Black death” but pretty much only in the ML or Sprinter versions

 

[mersum1es]

Lots of “Black death” but pretty much only in the ML or Sprinter versions

I think its because relaitevy higher miles than passenger cars...

 

[Blobcat]

I think its because relaitevy higher miles than passenger cars...

Not the ML, sprinters I can understand

 

[robin.large]

I'd just go for straight fuel issue. Anything 'engine' would make unmistakeable noises. Given the inertia of a crank and pistons the sound of a breaking crankshaft would be impossible!
Fuel pump failure would be my best guess

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[gassed up]

I've been fooling around with internal combustion engines for 50+ years and I can't say that I've ever seen a crankshaft that has snapped in normal service. It certainly wouldn't be anything I would ever consider in a diagnosis. To do a compression test you would need a rotating crankshaft? Diagnostic oxymoron

 

[LostKiwi]

I've been fooling around with internal combustion engines for 50+ years and I can't say that I've ever seen a crankshaft that has snapped in normal service.

948 and 1098cc A series engines were known for it.
The big end journals and main bearing journals had no overlap and as a result the crankshaft would break through the web.

 

[Taffy7hfa]

I once had an 11 month old Nissan Navara that decided to let one of its big end caps break free at 90mph on the motorway, Rodney decided to make a break for it via the sump, that was an interesting experience. Kinetic energy is a powerful force, I can only imagine the chaos that would result from a snapped crank, unless the engine was idling I'm pretty sure it would be quite savage and probably unmistakable.

 

[joderest]

We will all have to wait to see what the end result of this fault is, as mentioned could be one of many things and that makes it difficult to offer advice.

 

[ajlsl600]

When these modern,higher rpm engines let go there is often bits everywhere
No compression.1cly or all? Determined by?
Remove top cover.get spanner turn engine see whats moving. Do not use starter...

 

[LostKiwi]

When these modern,higher rpm engines let go there is often bits everywhere
No compression.1cly or all? Determined by?
Remove top cover.get spanner turn engine see whats moving. Do not use starter...

And while turning crank from front see if TC moves with no slop in the movement.
i.e if one moves the other should move immediately.

If not then you might be lucky and have a broken flex plate.

 

[ajlsl600]

In older days you could hear if link plate tinny grating sound
Find a place,starter hole?jam ring gear if can tutn front pulley left right,at all you have prob.
As asked .motor just stopped dead?no noise? Money wud be on chain.but if so I wonder how comp test carried out?

 

[Overread]

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.