5.5L 2009 Merc a273 - Can you repair a piston problem?

[dvb247]

Hi guys,
I thought I would throw this out in to the MB tinterworld to see if my rather poorly engine can be fixed.

Quick history, bought a CL500 that the last owner ran through a puddle, a large one, one that pushed the water up through the grill and down the engine.

The engine turns over and starts but only 7 pistons are moving up and down as they should, 1 is resting at the top of the cylinder when the crank is turned with a torque wrench.

So my question is can this engine be repaired by a V8 specialist? I would think this type of problem is bread and butter to them, new cylinder sleeve, new piston, or would that be me painting a to simplistic picture?

Any advice welcome?

 

[GordonTarling]

If one piston isn't moving, either the piston has broken in half, or the con rod has snapped. Apart from that, if it ingested water, there's likely to be lots of other damage. A replacement engine would probably be your best bet. Hope you got the car cheap!

 

[camerafodder]

Ahh piston broke, so am I mate!

Seriously though, any engine repair specialist worth his salt should be able to asses that problem for you and you can make a decision from there. As Gordon has already said though, proceed with caution as water ingress damaged engines are usually damaged quite badly.

 

[corned]

Lots of caution required here.

You may be lucky and it is just a 'hydraulic'ed cylinder, and that only the one has borne the brunt of the problem. Certainly sounds more like a broken conrod than anything else. The problem with that is that the forces imposed on a conrod in order to break it are staggering, so you will have to consider the possible (likely?) knock-on effects of where and how all that energy was dissipated - bearings, main journals, crankshaft, and so on.

You say the engine still runs. Is it making any untoward noises (apart from the off-beat nature of only firing on seven)?

Personally, I would not start it to find out, as sooner or later that broken conrod/piston is going to pick up on something and then you're in real trouble.

My advice would be to get a specialist to come to the car and thoroughly endoscope the engine. There's no point guessing at any of this.

Then you will know where you stand.

If you're a really lucky blighter, it may just be the piston crown which had broken off the piston body, but I think your luck would have to be really well in for it to be only that.

Good luck - I hope it is worth repairing.

 

[dvb247]

Yes got the car cheap as a salvage car.
No water evident in the engine at all so thats a mystery?
Endoscope sounds like a great idea many thanks for that.
Con rod is a definite we think.
When it started it sounds like the snapped rod was wacking the bottom of the piston so we immediately turned off the engine!
I have need told that no engines these days are "over engineered" they are all built now to work very close to their operating parameters to save costs (F1 springs to mind!) so the thoughts are that it would not take much to snap a con rod, but I do need a recommended V8 specialist in the North West to talk to!

 

[nick mercedes]

Yes got the car cheap as a salvage car.
No water evident in the engine at all so thats a mystery?
Endoscope sounds like a great idea many thanks for that.
Con rod is a definite we think.
When it started it sounds like the snapped rod was wacking the bottom of the piston so we immediately turned off the engine!
I have need told that no engines these days are "over engineered" they are all built now to work very close to their operating parameters to save costs (F1 springs to mind!) so the thoughts are that it would not take much to snap a con rod, but I do need a recommended V8 specialist in the North West to talk to!

It's Hydrolocked, there's no point messing around with an endoscope, the engine is going to have to come apart in anycase.

Perhaps you'll just get away with a rod?

But it depends on the state of the crank and the bore.

Looking at the EPC the rods are shared with M272 V6s (of which I have a Hydrolocked one), so second hand parts should not be too much of a problem to keep the rebuild viable.

 

[dvb247]

Thanks Nick, what does hydrolocked mean?
I think I am going to sell the car as is, I was going to keep it and sell my AMG K2 but I don't have the time to sort this out, also don't have anyone willing to have a look a the engine either!
Shame really but once running that car will be an awesome car for the next owner!

 

[corned]

There's every point in endoscoping the engine.

There is no point going to the expense of dismantling an engine which a quick look with a 'scope tells you is completely fooked!

 

[Howard]

Hydrolocked is where the cylinders fill up with water , as we all know , water doesn't compress , so bits of engine fall apart.

 

[nick mercedes]

There's every point in endoscoping the engine.

There is no point going to the expense of dismantling an engine which a quick look with a 'scope tells you is completely fooked!

It's goint be a waste of time, either the rod is bent or has snapped, best course of action is to take the sump off and see what's let go.

 

[nick mercedes]

Thanks Nick, what does hydrolocked mean?
I think I am going to sell the car as is, I was going to keep it and sell my AMG K2 but I don't have the time to sort this out, also don't have anyone willing to have a look a the engine either!
Shame really but once running that car will be an awesome car for the next owner!

As Howard says, it's sucked in water and bent something.

Is there nobody willing to look at the engine??

It might not be terminal.

 

[grober]

Rebuilding the moving bits pistons, rods valves etc is fine. You major headache will be any problem with block damage which may make the engine beyond economic repair.
Some background :- Are Mercedes Benz and Porsche engines rebuildable?