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Discussion Starter #1
I can't quite find a definitive YES or NO answer.

There are a ton of complaints, threads & a few YouTube videos showing how the m272 m272 engines suffer from failed Intake Manifold Swirl Flaps (and external linkage).

I did recall a thread or two on a rubber hose MB built into the manifold that can fail with age & requires big fix OR new manifold

What seemed weird was that I only saw that complaint on the R129 forums - thought we shared the V-8 M113 with them ?

Can any if you Benz veterans set the record straight on which Intake Manifold issues are specific to our m112 & m113 powerplants ?

Many thanks- David
 

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2000 ML55 sold? 2013 ML500,? 2015 C250 estate wagon, 1927 Dodge 4 sedan, 1929 Dodge
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There is a linkage inside the intake at the front, that can come apart and will leave only one set of diversion flaps working which leaves only one bank open or closed.
The rubber hose can be replaced or repaired but to replace it you need to take the plenum chamber apart. It’s glued together but does come apart after a good soaking.
If it fails it just means the air will take the long or short path which ever way the flap is positioned when it fails.



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This is the linkage that comes apart.


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Discussion Starter #6
Ok Matt - thanks. Questions:

Is this on both m112 & m113 ?

What are symptoms ?

Is error code set if fault occurs ?

Do we also have the "rubber hose built into intake manufold" that goes rotten & causes vacuum leaks ?

I'm trying to sort this all out.

I see only a modest # of threads describing this but the later m272 / 273 seem to be waaaaay more troubled in this area.

My engines are running nice but trying to be pro-active here.

Thanks for your input so we're the wiser...

David
 

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Ok Matt - thanks. Questions:

Is this on both m112 & m113 ?

What are symptoms ?

Is error code set if fault occurs ?

Do we also have the "rubber hose built into intake manufold" that goes rotten & causes vacuum leaks ?

I'm trying to sort this all out.

I see only a modest # of threads describing this but the later m272 / 273 seem to be waaaaay more troubled in this area.

My engines are running nice but trying to be pro-active here.

Thanks for your input so we're the wiser...

David
It can happen on both engines.
Probably only symptoms are lack of torque and maybe a lagging throttle response but you would really have to know your engine to pick it.
It wouldn’t throw a code because the vacuum solenoid still operates as normal.
Yes we do have the vacuum hose underneath the intake but there is repair kits out there. Witek posted it not long ago. You can do that repair without pulling the manifold apart but it still needs to be removed.


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Discussion Starter #9
It can happen on both engines.
Probably only symptoms are lack of torque and maybe a lagging throttle response but you would really have to know your engine to pick it.
It wouldn’t throw a code because the vacuum solenoid still operates as normal.
Yes we do have the vacuum hose underneath the intake but there is repair kits out there. Witek posted it not long ago. You can do that repair without pulling the manifold apart but it still needs to be removed.


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Excellent info.

So we would do 2 upgrades / repairs on either V-6 or V-8:

1 - the "flap linkage repair"
2 - Re-do leaking rotten (internal to manifold) vacuum hose replacement?

(Either one requires manifold removal.)

But not until loss of performance is evident ?

Here's a DIY I found on ML430 to rebuild the Intake Manifold - Upgrade Vacuum hose. Looks a bit involved but saves $800 vs new manifold.
 

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Discussion Starter #10 (Edited)
Here:

Is that similar to repair Witek referenced ?

Interestingly, the Wiki you referenced lists only these MB engines:

[TECH Q: Anyone else have trouble pasting text or link from Smartphone after you've typed ???]

Next post....
 

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Discussion Starter #11

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Discussion Starter #12
Ok, so I think I've got this figured out. Please correct me if I'm wrong, btw.

Our m112 & m113 engines have a simpler 'internal flap low / high runner' mechanism inside them, and its run by vacuum from the rubber hose that goes up from bottom at front bottom of Intake Manifold.

If this rubber hose deteriorates, which they all eventually will, then you get a vacuum leak, and the flaps get stuck in whatever position they were in upon rubber hose failure - which is more like slow disintegration.

When this occurs, one either buys a new replacement manifold (seem to be $600 for V-6, $700 for V-8, PIerburg OE brand) OR they figure out a somewhat intricate Rubber hose upgrade which involves taking apart the manifold that Mercedes didn't design to be disassembled, but can be done, and one upgrade using a kit like this:

Kit Illustration (picture posted)

Do I have that right ?

What is confusing is that I don't see a lot of threads - some few - but not tons of them - talking about this, but not as many as might be assumed.

Is this a RARE failure ? How many of you have had this happen - (I know some of you are 2x my 160k miles) ?

What were the symptoms & how did you fix ?

Thanks for any input you veterans can offer !

David in Texas

PS: I also learned it is the later m272 / m273 engines that have the far more complex plastic external linkages on their Intake Manifold, that nearly always fail and cause owners grief - bummer for them....
w163 manifold rubber line upgrade kit.JPG
 

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Your not really going to notice the flap failure in any way.
If the vacuum hose fails the diaphragm solenoid will cease to work causing the flap to stay in the open or closed position, (I’m not sure without going back over notes. )
You can check the flap operation by giving the throttle a quick hit and you should see the diaphragm pull in. If it doesn’t you most likely have a cracked vacuum line.
The internal arm that operates the opposing flap can come off making only one side operational. You can’t check this unless you remove the manifold or get a really good camera and stick it up it’s ass. Lol.
I hope I’ve explained that well enough, witek may be able to add some better info on it all.


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Discussion Starter #14
Ok Matt that makes sense.

From your take, it appears: Our m112 / m113 engines don't suffer MASSIVE power loss or run so POORLY that the failure is obvious or debilitating, yes ?

I bet the resulting Vacuum leak is probably the worst part of it.

What was the condition of your Intake Vacuum hose on any of the manifolds you had it on ?
Any deterioration or cracks ?

That kit I listed the link & picture for is supposed to fix the issue.

Yet, the page showing it is short on details - it looks like just a new hose, but there MUST be something more to it than just that, like a special procedure to install, or that it restores function, perhaps ?

If one cannot tell the failure, why not just dab RTV sealant over the "broken" hose as it exits the lower front mainfold, fixing the Vacuum leak and be DONE with it ?

I'd appreciate it if Witek could comment on the nuances of this issue - has he, for example, used that kit that he had linked to - that I posted too above.

Cheers - David
 

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Ok Matt that makes sense.

From your take, it appears: Our m112 / m113 engines don't suffer MASSIVE power loss or run so POORLY that the failure is obvious or debilitating, yes ?

I bet the resulting Vacuum leak is probably the worst part of it.

What was the condition of your Intake Vacuum hose on any of the manifolds you had it on ?
Any deterioration or cracks ?

That kit I listed the link & picture for is supposed to fix the issue.

Yet, the page showing it is short on details - it looks like just a new hose, but there MUST be something more to it than just that, like a special procedure to install, or that it restores function, perhaps ?

If one cannot tell the failure, why not just dab RTV sealant over the "broken" hose as it exits the lower front mainfold, fixing the Vacuum leak and be DONE with it ?

I'd appreciate it if Witek could comment on the nuances of this issue - has he, for example, used that kit that he had linked to - that I posted too above.

Cheers - David
When the problem or flaps are repaired you notice the difference in performance is better. As I said earlier you would really need to know your engine to feel it straight away as it failed. It’s not one of those type of things like a cylinder dropping out of something like that.
When I repaired mine I basically polished the full inside of the manifold and got rid of every little lip and bump out of it.
The difference in performance after doing that was quite amazing.


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Failure of that vacuum hose is not that common. Most failures are by DIY as in Damage It Yourself. Severe oil leak from oil plug in the engine V valley will damage that hose. It is not oil resistant.

My advice is if it is not broken don't look at it and don't play with it.

In case of failure manifold flaps will stay in open position. Vacuum element that works them is spring loaded. Vacuum closed, no vacuum spring force open.
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Discussion Starter #17
Matt, Witek:

That's great to hear.
No need to worry over it then.
That explains why there is some mention over it but not too much.

From my research it's the later series m272 / 273s that are unable to ignore their Intake Maifold breakage issues !

Another reason to prefer our w163's, right !?


Cheers - David
 
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