M156 rebuild after bent conrod

[zenman63]

As above I have stripped down a 2011 engine after it bent a conrod jamming the crank solid.
All very good inside and has the revised SLS tappets and head bolts.

New rod from MB parts £154 so not to bad.
I have a couple of questions that I cannot find clear on my Wis.

The bolts in the cam caps, do they need replacing??
The bolts in the cam adjuster again are they stretch bolts or not?

I have all new mains and big end bolts from MB parts.

 

[AMGeed]

Any idea what happened to cause the conrod to bend?
Pretty unusual thing to happen to an AMG engine

 

[zenman63]

Its more common than you think, 28000 miles and had an injector over fuel one cylinder, and bingo one bent rod, I will get some pictures up.

 

[grober]

If you look under engine timing/tightening torques for the M156 engine you should get the info you want. Not sure if this applies to your specific engine but on one M156 example
The camshaft adjuster to camshaft M12 BOLT is given as 45Nm+90 degrees making it a stretch. The camshaft bearing caps M6 bolts settings given as 10Nm would indicate they are non stretch-- but please check for yourself with your specific engine no because they may vary.

 

[AlexM]

Surprised the crank isn't bent too after a hydraulic lock - are you sure it isnt?

Sent from my ONEPLUS A3003 using Tapatalk

 

[zenman63]

No way, have you seen a crank in this engine? the rod is the week link for that reason.
Crank has 5 main bearings its not going anywhere.

 

[AlexM]

No I haven't, but I presume it's forged and is going to be pretty robust running 5 mains..

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[renault12ts]

Robust...sure. But 5 mains is not a big deal...most 4 cylinder engines have that. In fact the engine in a Renault12ts had 5...in the early 70s. The reason being that when Renault first exported to the US the engines only had three...and didn't last on long cross desert journeys.

 

[Flyinspanner]

I'm I would definitely get the crank checked (and balanced) after such a shock loading, for true and crack detection.
Maybe swap out all the shell bearings for the same reason, they may have deformed due to shock loading.

Most MGBs had a 5 bearing engine, it's nothing special, but reduced crank flex (engine failures), pretty standard engineering. (And they were running much less power than yours.

Hope it's all ok, the cost of check will be much cheaper than a second 'incident'.

 

[zenman63]

It's all fine, you can turn it with one hand.
It's not just 5 mains the block is split along the crank centre line, so it's in the middle of the block with 20 stretch bolts holding it in.

 

[Celicasaur]

Ouch man, I had read of this issue in the States, but it's the first time I've read of one on these shores. I hope you get it sorted really soon buddy and it's not too costly.

 

[mounty3279]

Can you put some pics on?
It's a big lump to pull apart is that. Sounds like your well into it though.

 

[Bobby Dazzler]

It's not your engine is it zenman63?

 

[zenman63]

Not out my ML no but it's going in soon.

 

[Bobby Dazzler]

Not out my ML no but it's going in soon.

Ooh, are you tuning it? What's happening with your old engine?

 

[zenman63]

Nothing wrong with my engine but as this if fresh and with the later revisions with the SLS tappets and head bolts, black plastic rocker covers etc its going in and then I will sell my ML engine.
Couple of differences on the lower engine to the 204, the lower crank case and sump along with the oil pump is all unique to the w164 so will swap all that over.
Looking to see if anyone has had the ML engine out the top as Wis says its out the bottom.

 

[ftb]

You're not balancing the crank? Or checking if it's even true?

 

[zenman63]

You're not balancing the crank? Or checking if it's even true?

Its fine, its not that hard to bend a rod, engine bottom end is rebuilt now and like I said you can rotate the crank with just your hand, impossible if the crank had any defects.
Crank is already balanced.

 

[bellers]

Check the crank. I did one and the shock loading when it locked flattened the mains and big ends and threw the crank out of balance. Worth having it spun up and balanced.

 

[zenman63]