I would recommend when you do maintenance for your car then perform maintenance services for intake manifold as well: cleaning oil and dust, check rubber seal and replace it if necessary, re-sealant area around flap and entire intake manifold cover to avoid vacuum leak as well as bushing flap (white pieces plastic on the photo) drop off into combustion chamber.

 

Ah YES=== another 'OEM impossible to replicate' silicone sealant job. The surfaces needing sealing must be COMPLETELY OIL FREE--dry, no remaining oil film at all. This REQUIRES chemical cleaning with a chlorinated solvent such as 'brake cleaner' that is not hydrocarbon based. The new silicon MUST moleculary BOND TO both surfaces, not simply be there and be squeezed to make a seal. Once you think all is clean, wipe with laquer thinner and clean none linting cloth. Even a tiny amount of oil or old sealant will prevent the new sealant from bonding to the metal/plastic surface. Without the sealant to metal BOND, oil WILL wick through and leak. Engine oils contain an 'oiliness additive' to improve lubrication propensity and ensure all the surfaces are 'oil wet' and not just oil splashed.

One must also watch the 'skinning time' and be sure the two surfaces are well connected before the sealant begins to form a 'skin.' The skin usually will not bond to the other surface. Be sure and use the MBZ official REPAIR sealant for this job. At the factory , robots apply the sealant and place the new, chemically clean parts together---much faster than humans can so we need longer 'skin' times.

 

I wonder, how did the world work before this new type of "impossible to replicate" gaskets were invented?

 

The 'old days' 0f all mechanical devices using internal lubrication are limited, Petroleum lubricants are less than 100 years old. Earlier lubricants were beeswax and various animal fats. Early 'gaskets' were animal skinns. The internal combustion engines gradually becames more highly developed and used newly invented materials to better contain the lubricants and coolants. Sheets of ground up and glued together cork particles were and are popular. Automobile engines are one of the more difficult sealing services.
Prior to accurrate industrial robot applicators, engine were sealed with sheet gaskets of various synthetic materials and laminated 'copper/asbestos' laminates. The first 'liquid' sealants were developed for the radial aircraft engines of WWII. It was made from insect shellac, and is still in wide use today. It adheres well to oily surfaces and remains flexible and resistant to gasoline. Aluminum alloy parts expand and contract much more than cast iron and sealants must be able to flex much more to maintain sealing.
German engines seem to be much more prone to oil leakage from poor sealing designs than others. They would be leak-tight for a while until the sealants would lose adhesion to the parts and allow oil leakage. One can argue the root cause of the failures was poor application or poor sealant. However closer attention will find the only joints subject toleakage were those where more than 2 surfaces were meeting. The computer design tools did not leave enough 'clearance' between the precision manufactured components for an adequately thick sealanf layer. The resultant extremely thin seal has to absorb too much differential movement across that ultra-thin seal, tearing it loose from the surfaces to be sealed. The early V-12's had 'certain to leak' joints where five (5) precision machined surfaces meet with very tiny contact surfaces (for sealant adhesion)and very tight 'clearances' resulting is very very thin sealant layers. With continual heat/cool cycles and slow hardening(ageing) of the sealant, eventual failure ( usually between 15-30 000 miles, and leakage, starting with a little seepage, would result. It was(is) a costly repair to replace the leaking seals.
GM has experienced a few major screw-ups as well--a 'world class instance' was the head gaskets for the basic VEGA engine. That engine wsa developed with an aluminum alloy head and was 'bullet proof'' in lengthy testing by Oldsmobile in automotive and marine powerplant services. When GM decided Chevrolet was to use the engine, Chevrolet 'Cost Engineers' decided to use an idle Cast Iron cylinder head manufacturing line instead of building a modern aluminum alloy manufacturing facility. Then they decided to use a low cost non metallic head gasket rather than the more expensive full copper jacked design used by Oldsmobile (which never failed). The different expansion rates of cast iron head and the aluminum alloy 'floating' cylinders would rip the gasket apart, allowing coolant to leak into the combustion chamber. The antifreeze containing coolant would displace oil from the cylinder surface and cause lubrication failure and destruction of the engine.









The exquisitely precise 'formed in place' seals used in recent years enabled much more complex shapes of single parts, reducing assembly time and parts inventory costs. However, the newer sealing materials
are not as 'forgiving' as previous generation ones.

 

Once again, I bow to wisdom...

 

1960s: A cast iron 4.7l engine produces 200 to 270 HP and weighed 475+ pounds. Under normal conditions you're doing well to get 100K miles before it needs rebuilding.
2010s: An aluminum 4.6l engine produces 400 to over 500 HP, and weighs about the same...

Time and technology march on.

 

Hi @saskloppers any progress or update on this?

 

Hi Minh.

Don't laugh.

I've not touched the car as yet. Really been too busy with other work and it's been gathering dust. I spoke about this yesterday and must get my backside in gear. Will probably have to wait another two months.

Sorry. Will keep you posted.

Regards

 

Hi Minh.

I finally took my car apart on Friday and it's running again since yesterday.

Here's what I found

A flap broke and lodged itself between the inlet valve on #1 cylinder and the seat. This obviously caused the loss of compression. After turning the engine to have both valves on the intake open, I took a long nose pliers and pulled the piece out. (Note the "J" shape remnant in the attached photograps)

Next I stripped the intake and found chaos. The primary flaps near the injector ports and it's actuator is in 100% working condition, but the secondary flaps used to control the length of the intake runner broke. As I understand how this system is supposed to function I removed the remaining flaps and their shafts, and whatever debris I could find. What bugs me, is the fact that not a single bush was anywhere in sight! These all came out and was blown out through the cylinders! (WTF were Mercedes Benz THINKING when designing something THIS horrible??)

I also used expanded foam, closed all ports and vacuum cleaned all the grit and debris, then washed with gasoline, and used air to dry. I also proceeded to clean inside every cylinder to ensure that no grit remained inside.

After that I cleaned the intake. It was really terribly dirty with a lot of residual grease and gunk. Not even being able to clean it properly with an extremely good degreaser, I then submerged the whole thing in a tank and cleaned with paraffin. Then washed with degreaser and water after to let it dry properly.

I assembled the intake using the original flap guides but minus the tumble flaps, in order to experiment with the thing. I want to determine if the car would show any loss of power, rough running and CEL errors. I also used the old worn out shaft to blank the actuating lever rod hole in the intake with silicone.

Well, I have to say the car actually feels awesome. The engine is a whole lot more responsive for some reason. However...

At idle the car has a slight misfire. Now this can be caused by three things.

1. The ECU is not happy with the short intake tract at low speeds. (Long runners are designed for bottom end function, to increase velocity and torque.
2. I re-used the old intake metal plate gaskets with no sealer whatsoever. Perhaps there is a vacuum issue with some air being sucked in at idle, and this will be evident when car is at idling speed as the throttle valve is virtually shut, causing a faulty mass airflow signal to trip the CEL, which my Autocom interprets as a "permanent intake error"
3. Upon re-assembly I broke the vacuum tube off of the vacuum actuator solenoid. Being weekend with no part shops open, I did a cyano-acrylate repair. It is possible that the vacuum line is now blocked.

So considering how minimal the actual damage is, I am going to do the following.

1. Tomorrow I will remove the intake and replace the vacuum actuator solenoid with a new module. Also I will use copper spray on the old metal plate intake gasket to ensure a better/proper seal.
2. Reassemble, do all adaptations after clearing fault codes and test the car again. If it runs good, I will leave it at that. If not, I plan on the following:

I will remove and strip the intake again. This time I will blank off the secondary flap apertures and re-assemble, to test again.

All that could possibly happen is that the car might lose a little top RPM power. However, even so, I will not be bothered as the car has enough power as it is. But this might be a solution in a worst case scenario.

Anyway, once I know the result, I will post this with photographs of how I aim to blank off the secondaries, forcing air through the long runners.

After establishing that, I will install a new manifold. So it will be a good guide of what is a possible solution to these intake issues.

I include some random photos:


Cylinder #1 with broken tumble flap stuck in intake, preventing valve from fully closing

Tumble flaps removed. Note the bottom RH item. This is the tumble flap remnant that was removed from cylinder #1

Bare intake housing, cleaned

Intake housing with tumble flap guides installed, no tumble flaps

 

mutually assured destruction - nice

 

I don't really understand what you are inferring here?

Do you care to elaborate please?

 

An update......

I've no direct need for this car and has parked it for two years as I worked on my engineering projects for clients. Been tremendously busy though I'm retired!

Interesting thing is I removed the flaps from mine and have driven it a few days now. I do get a CEL as I've invariably broken the plastic vacuum control valve tube when I installed the manifold after the mod. Ordered a new one and will collect tomorrow morning. Established with the Autocom CDP + that this is definitely the reason for the CEL.

Also had a slight misfire at idling which I traced and cured to a dirty injector. Some good injector cleaner solved that issue. The engine's running as smooth as silk now.

Now I am considering engineering a replacement set of flaps using a solid metal actuator bar inside the manifold and water-jetting new metal flaps. (Considering inconel but I might opt for brass or aluminium.) I want to see if it is possible to use the car without flaps first as I've removed many from BMW manifolds in the past with no setbacks or gremlins afterwards.

What I found particularly surprising is that the engine response at present has not been diminished in any way, on the contrary. The car is actually terrific and engine response under acceleration is really awesome! (Who cares about a little increased fuel consumption and smog anyways, right?)

The other thing I'm looking into is working on the flaps by removing the manifold top cover without removing the the entire manifold. This is doable in my opinion and I am about to start with the thing in a few minutes.

It's been an interesting ride fiddling with this manifold thus far. I think it's eventually going to end with an engine that breathes and combusts better when I'm done.

So why replace when there are other solutions?

I will keep contributing to this thread advising my findings.

Have a lovely day, y'all!