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  #1  
Old 05-29-2012, 03:55 PM
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OM606NA (1996-97) pressure control flap removal

The OM606 normally aspirated engine was used in the 1995 (W124) and 1996-97 (W210) E300D models. The intake air system includes two "resonance" flaps that adjust the effective length of the intake manifold for improved engine torque. These are well described in the 1995 "Introduction to service" manual published by Mercedes.

Also in this engine is a third flap just ahead of the EGR valve. This flap is described as an "intake manifold air pressure control flap" but its purpose is a little hazy. I've finally decided that it's there to lower the air pressure in the intake manifold and thus encourage more exhaust to be sucked through the EGR valve. Since I have temporarily disabled the EGR valve (as an experiment to see if intake manifold cleanliness is improved) the pressure control flap is no longer necessary. I decided to remove it.





The flap is inside the section circled in red. The flap is operated by vacuum and (in the 1995 version) there is a mechanical link to the accelerator mechanism to open the flap at high accelerator position. This reminds me of the choke pull-off linkages that carburetors used to have (still do?).





With the section removed and on the bench, the flap can be seen. It is secured by two Phillips screws. I had expected the flap to be riveted on or secured in some other non-reversible way but the simple screws are not even peened. I removed the screws and then wiggled the flap out of its slot in the rod.




With the flap removed, I put the assembly back together. Everything connects just as it did before and the engine looks completely untouched. For those who wish, the entire assembly, EGR valve, and vacuum plumbing nightmare (under the air cleaner) could also be removed. You'll have to fabricate a piece of pipe to replace the pressure control flap assembly.

The flap and screws will be put away in a safe place while I determine the changes, if any, to the engine. In one short drive I've noticed no difference good or bad. Note: if you ever put the flap back, be sure to use a little blue Loc-Tite on each screw. These is a place where a loose screw could do a lot of damage.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #2  
Old 05-29-2012, 04:37 PM
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I've done similar, since disabling my EGR, but locked the flap in the fully open position with a cable tie. Like you, I'm not sure it makes a whole lot of difference (if any) but I figure it can't hurt to have a bit more airflow.
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1993 320TE M104
---------------------------------------------------
past:

1983 230E W123 M102
1994 E300D S124 OM606 (x2)
1967 250SE W108 M129
1972 280se 3.5 W108 M116
1980 280SE W116 M110
1980 350SE W116 M116
1992 300E W124 M103
1994 E280 W124 M104
----------------------------------------------
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  #3  
Old 05-29-2012, 06:16 PM
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Thanks for the new project. Now has anyone removed the cat ? (Or particle filter )
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Old 05-29-2012, 07:26 PM
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Quote:
Originally Posted by ottomatic View Post
Thanks for the new project. Now has anyone removed the cat ? (Or particle filter )
That is my next project, I imagine with almost 200k mine is good and plugged, even though my car has only really resided on the interstate for 20+ miles (usually more) at a time. I believe, last time I was under my car, that it has two inlets from the split pipes on the exhaust headers, should make installing a couple of bypass pipes a little more of a challenge. I know there is at least one guy on benzworld that has done it on his 95, said it made a nice power improvement and picked up a few MPG's, plus he only had maybe 70k on his cat.
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  #5  
Old 05-30-2012, 12:33 AM
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Not much of a challange. MagnaFlow/2 1/2 in. dual inlet x 2 1/2 in. single outlet x 10 in. overall universal stainless steel Y pipe transition (10758) | Exhaust Pipe and Adapter | AutoZone.com
+ now it has me thinking of a full flow muffler. Maybe even straight pipe it.
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  #6  
Old 05-30-2012, 12:41 AM
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Originally Posted by ottomatic View Post
That will make it easier for sure, I'm thinking maybe adding some kind of resonator, or like you are mentioning, another full flow muffler in place of the cat to keep it nice and quiet while still increasing flow over what I bet is a nicely sooted up cat at this point. I don't need a lot of power to be happy, but a little extra power and mileage certainly would be nice.
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  #7  
Old 05-30-2012, 12:50 AM
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Quote:
Originally Posted by ottomatic View Post
Thanks for the new project. Now has anyone removed the cat ? (Or particle filter )
I think it would depend on the local laws and whether the pipe gets sniff tested annually for registration.
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Old 05-30-2012, 01:53 AM
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Originally Posted by benedict View Post
I think it would depend on the local laws and whether the pipe gets sniff tested annually for registration.
A lot of states here have snap testing, I may, or may not, have removed the cat on my 7.3 Powerstroke. It had over 200k on it at the time and I gained about 2mpg highway, plenty of power, and oddly enough, identical opacity (what the snap test measures) to when I had the cat installed. It was all sludged up in there at that point, even though the truck runs great and never really spent any time in town, just like my Benz.
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  #9  
Old 05-30-2012, 07:25 AM
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Jeremy,

That isn't green coolant I see in there is it?
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  #10  
Old 05-30-2012, 09:43 AM
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Jeremy,

Is your accelerator pedal a bit on the heavy side?

Just noticed you have an extra spring added ontop of the accelerator cable linkage. If you grease up the ball joint sockets on the link going between the IP and your cruise control, you can probably do away with the extra [ return] spring. Need to take crossover pipe off: FSM recommends transmission fluid as lube but I've had no success with that so I used a waterproof Teflon grease.
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  #11  
Old 05-30-2012, 09:53 AM
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Quote:
Originally Posted by Bio300TDTdriver View Post
Jeremy,

That isn't green coolant I see in there is it?
Bio300tdt, I had the pink zerex stuff in mine until my recent fluid change. I ordered the factory stuff from MB and it was green. I did question the parts guy so he printed off a piece of paper showing the correct spec for my car, which matched the spec on the bottle. Apparently Mercedes green coolant is different in chemistry to the run of the mill green.

I hope it's right as it's pumping through the veins of my e300d right now.
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Old 05-30-2012, 09:59 AM
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Quote:
Originally Posted by thatguy View Post
That is my next project, I imagine with almost 200k mine is good and plugged, even though my car has only really resided on the interstate for 20+ miles (usually more) at a time. I believe, last time I was under my car, that it has two inlets from the split pipes on the exhaust headers, should make installing a couple of bypass pipes a little more of a challenge. I know there is at least one guy on benzworld that has done it on his 95, said it made a nice power improvement and picked up a few MPG's, plus he only had maybe 70k on his cat.
I have the same car and have driven around with the cat removed and a Y pipe in place - it droned like crazy enough to make me mad on a 10 mile trip, I also lost some low rpm pull power, not that the NA 606 has a lot but it could be felt. I put on a generic magnaflow diesel CAT and everything is quieter now and the low rpm pulling power is back. to fit the diesel cat you need this Y pipe as the cat only has 1 inlet.

anyway on the same topic I need someone with experience in exhausts to fix a problem Im facing, ever since I bought the car I have a strange leaky exhaust noise right at 2500 - 2800 rpm and it only increases with accelerator position when the car is moving and the engine is under load. I have had it checked at a number of exhaust places and there is no leak anywhere.

I read about it and I think its called header tick usually caused by aftermarket installations, its more like the exhaust pipes are ringing with the firing pulses of the engine - the firing pulses can be heard at the tail pipe too, One shop said that it maybe that the mufflers are bad internally causing this noise - but did not take on the job because he was not sure. btw my exhaust has the original front pipes mid and rear mufflers and new ones for this model are very expensive because the older turbo diesel rear muffler is smaller than the one used on this NA engine car, so Im a little hesitant in spending a bunch of money and not fix the problem.
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  #13  
Old 05-30-2012, 02:01 PM
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Green stuff

Quote:
Originally Posted by Bio300TDTdriver View Post
Jeremy,

That isn't green coolant I see in there is it?
Good eyes! Old picture! Came with the car! The engine now has MB coolant and distilled water plus a bottle of Redline "Water Wetter" as an experiment. I've noticed no change in cooling due to the Water Wetter but at least the coolant hasn't turned to sludge, as some nay-sayers have claimed.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #14  
Old 05-30-2012, 02:03 PM
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Return spring

Quote:
Originally Posted by benedict View Post
Jeremy,

Is your accelerator pedal a bit on the heavy side?

Just noticed you have an extra spring added ontop of the accelerator cable linkage. If you grease up the ball joint sockets on the link going between the IP and your cruise control, you can probably do away with the extra [ return] spring. Need to take crossover pipe off: FSM recommends transmission fluid as lube but I've had no success with that so I used a waterproof Teflon grease.
Like, "a lot" heavy! I wondered about the extra spring -- the linkage seems to work even without it. I'll clean all of the links and try without the extra spring. Thanks for the suggestion.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #15  
Old 05-30-2012, 02:19 PM
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the spring looks like a cover up fix for the sticky accelerator due to the cruise control arm ball sockets shrinking in cold weather. Grease works good like mentioned, if it still sticks its best to renew that little arm.

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1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)
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