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W220 2003 Update S500L, W204 2008 C220 CDI
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Discussion Starter #1 (Edited)
Have just got around to changing the fluid in my NAG 2 {Neues Automatische Getriebe 2} New Automatic Gearbox 2 or 7G-Tronic 7-speed (722.9) 722 901 00 003 799 (Build Code 427 AUTOMATIC TRANSMISSION 7-SPEED).

I spent ages searching the Forum to make sure I had identified the correct parts. I concluded mine is the updated transmission (which started in August 2003) ie the 7G-Tronic or 722.9 NAG2 with updated pan which has a bevelled or sloping aft end with round indentations, a white overflow pipe and uses red 236.14 fluid measured at 45C. I have yet to check the colour of the pipe.

I purchased the filler kit, filter, gasket, screws, overflow pipe, torque converter plug, drain plug washer and 10L of genuine M-B fluid but have been putting off doing the job for months.

Now that I have started I cannot find a drain plug in the torque converter. The access ports on my tranny don't match the one shown in BenzWorld's Elite Member G-AMG and MB World’s Member, johnand (John Anderson) who have published excellent write-ups on the DIY job.

When viewed from the rear I have two access ports
722.9 Transmission Viewed From Rear.jpg
722.9 Transmission Closeup of Rear Ports.JPG
and when viewed from the front I have one large access port on the torque converter housing. See photos.
722.9 Transmission Viewed From Front.JPG
I have rotated the engine according to the DIY instructions but cannot see any drain plug. I can just make out an engraved number on the actual torque converter, MB 112 032 02 47 MB. eBay has this shown as a W220 S-CLASS Starter Flywheel Flexplate, see photo.
W220 S Class Starter Flywheel Flexplate.JPG
So I presume I just go ahead with the rest of the job and ignore draining the torque converter?

Any advice much appreciated.

Regards, Brian
 

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Outstanding Contributor Always Remembered RIP
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I cannot find a 204 with the 722.901 box the full VIN number might help
 

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W220 2003 Update S500L, W204 2008 C220 CDI
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Discussion Starter #3
Hi Malcolm,
Thanks for the quick reply.
My VIN is WDB2201752A387356.
Brian
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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Not having much luck on this,, when it comes to draining the convertor it says "vehicles with a drain screw on convertor" So some do not have one
 

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W220 2003 Update S500L, W204 2008 C220 CDI
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Discussion Starter #5
Thanks for trying Malcolm. I did see a post somewhere where the DIYer had drained the trans fluid by opening one of the lines to the cooler in the radiator. If I remember correctly he had also fitted a trans dip stick so he could refill it through there.
I guess I just have to accept that my brand new, very expensive, M-B fluid will be diluted by the couple of litres of old fluid remaining in the torque converter.
What a stupid design by M-B! Everything else on the car is brilliant first class engineering, but this takes the cake.
Now that I have all the gear I plan to change the fluid regularly anyway so the fluid condition will improve each time.
I am hoping that the fluid change and new filter will improve the shifts as they have got quite noticeable lately. Not surprising with over 200,000Km on the odo and still the OEM oil.
Regards, Brian
 

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Brian from the pictures of your transmission I would say you don't have the drain in the torque converter, when compared to the pictures in the attached pdf. 1 large round for the one with a drain that is not present on yours.

Dean
 

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Discussion Starter #7
Thanks Dean,
That is what I had concluded as well. I had found the WIS article and noted the differences. See attached.
My trans has two smallish rectangular ports instead of the one large round one. I do have a large port on the forward facing surface but no drain plug that I can find.
Brian
 

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Outstanding Contributor
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Just flush it out. This is a picture of what I did with mine.
The red arrow points to the line linking the 2 spray bottles.
The yellow arrow to the gearbox inlet by the banjo bolt.
The green to the return line from the cooler by another banjo bolt.
The only problem with this setup was that the bottle feeding the oil into the gearbox didn't pump as quick as the bottle for the old oil filled. So I had to stop the motor and pinch off the link line and pump the oil in by hand twice, not a real problem as it still allowed me to completly replace all of the oil after the filter was changed.

Total cost for the setup was about $45.

Dean
 

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Thank you. I will be trying it again soon, but this time I think I'll try a 1 way valve in the line for the old oil. Then I can pump a bit of presssure into the bottles before I start. This may have it work the way I intended it to, may mean I only have to stop the motor once too.

Dean
 

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Discussion Starter #11
Ideas for a DIY 722.9 Transmission Flushing System

My 722.9 transmission torque converter holds 4L of fluid which is nearly 50% of the total capacity. Thus just draining the old fluid from the pan and not the torque converter will severely contaminate any new fluid that is added.
I have discovered that the torque converter drain plug was removed from the 722.6 in mid 1999 and that first generation 722.9 transmissions did not have one. It was reintroduced later.
Thus since my torque converter does not have a drain plug, flushing via the coolant lines seems to be the best option in conjunction with a pan drop, filter change and refill via the overflow tube, and finally setting the correct fluid level using STAR and the overflow method.
I have spent all day trying to design a flush system similar to that suggested by BenzWorld Member, pinkster (Dean) to suit my application. Apologies for the cut and paste cartoons but I like to see diagrams.
I would appreciate your comment and feedback on the next few posts before I start manufacturing this baby.
I am particularly interested in;
  • Question A. Can anyone please confirm the direction of fluid flow in the trans cooler lines?
  • Question B. To ensure virtually 100% of the vehicle's ATF is exchanged will require using 50 – 100% more new fluid than a simple drain and replace service. Therefore, is it a good idea to use cheaper fluid for the first the flush and then redo with genuine M-B fluid. This will mean changing the methodology below.
  • Question C. Dean can you confirm how much new trans fluid you used for a complete flush?
  • Question D. Is it a good idea to put a bypass valve in the flush system which can be quickly operated if the new fluid runs low or worse still, runs out?
  • Question E. Does anyone know what causes the solenoid valve ‘AD’ to operate? See Diagram below. When open, solenoid valve ‘AD’ bypasses fluid from the valve body and cooler to the pan.
TIA, Brian
 

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W220 2003 Update S500L, W204 2008 C220 CDI
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Discussion Starter #12 (Edited)
Understanding the 722.9 Transmission Cooling System

This is what I have discovered about the transmission cooling lines.
722.9 Transmission Cooling System Schematic.jpg
My observations so far.
All trans fluid pumped from the pan goes through the filter first.
All the trans fluid flows through the cooler unless the solenoid valve ‘AD’ operates and bypasses fluid to the pan. What causes AD to operate is TBD. The diagram shows it as a normally open valve. This means there are two paths for fluid to return to the trans pan; 1. via the AD solenoid and 2. via the trans cooler in the radiator. Because of this, installing a flush system in the trans coolant return line will replace some dirty fluid but not necessarily all of it. If the solenoid valve AD is open during the flushing process, some fluid will bypass the flushing system. Unfortunately this doesn’t seem to be avoidable.
 

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Discussion Starter #13 (Edited)
Physical Locations of 722.9 Transmission Cooling Lines

Now to the physical locations of my transmission cooling lines.
Later Note: I deleted the first image as it was wrong.
This new diagram is correct for my W220 2003 (Update) S500L 722.9 NAG2 7G-Tronic Transmission.
722.9 NAG2 7G-Tronic Transmission Location of Cooling Lines.jpg
Later Note: I have edited the following to make it correct for my vehicle.
My observations so far.
I have now confirmed the Trans to Cooler Line which is connected to the Transmission Housing on the right side and enters the Radiator at the bottom right corner is the Trans Cooler RETURN Line. I have now confirmed that the Trans to Cooler Line which is connected to the Transmission Housing on the left side and leaves the Radiator at the top right corner is the Trans Cooler SUPPLY Line.
On my W220 2003 (Update) 722.9 Transmission the Trans to Cooler SUPPLY Line is in two separate parts and has a connector installed, see Blue Star in diagram. My plan is to utilise this convenient and easily accessible connection to install the flushing system.
 

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Discussion Starter #14 (Edited)
Design Proposal For The DIY Transmission Flushing System

Later Note: I have edited the following to correct the direction of flow as my original assumption was incorrect and was misleading. It was confirmed for my vehicle after building and testing the DIY Transmission Flushing System. It cost me two litres of new fluid which was contaminated by the old dirty fluid flowing into the wrong container. The attached diagram is now correct for my car, a W220 2003 (Update) S500L with 722.9 NAG2 7G-Tronic Transmission.
Now to the design of the flushing system. It is based on the system suggested by BenzWorld Member, pinkster (Dean) and my searching the Internet
Most professional transmission fluid exchange machines use a bladder type system to hold the new fluid (usually about 16L). In operation the old fluid flowing from the pump to the transmission cooler is interrupted and the equipment inserted into the loop. The old fluid supplies the hydraulic force to exchange the old fluid for the new. Sometimes they supplement the pressure with a low pressure pump. The new fluid is returned to the pan, where it flows through the filter first, then into the pump, valve body, torque converter etc.
My proposal (now built and tested) is to open the trans to cooler SUPPLY line (left side) and using appropriate brass couplings and reinforced vinyl hoses to connect in the home made flush system as shown. The new fluid container is preloaded with say 4L of new trans fluid.
722.9 NAG2 7G-Tronic Transmission DIY Flushing System Connection Diagram.jpg
When the engine is started the trans pump will push the fluid from the trans pan through the valve body of the transmission including the torque converter through the SUPPLY line to the intermediate in-line connector, then into the Dirty/Old Fluid Container (BROWN ARROWS). The displaced air (WHITE ARROWS) transfers to the New Fluid Container thus pushing the new fluid into the Flushing System In-line Filter, then into the intermediate in-line connector, and to the trans cooler (PINK ARROWS) and from the trans cooler back into the trans pan through the RETURN line (GREEN ARROWS).
Theoretically no fluid should be lost in the process. (Confirmed)
The flushing should be stopped when the preloaded new fluid is expended or the colour of the dirty/old fluid looks clean, hopefully the latter.
Here is a picture of the DIY Flushing System showing the mating connectors.
DIY Transmission Flushing System with 722.9 NAG2 7G-Tronic Connectors.jpg
Here is a picture of the DIY Flushing System in use.
DIY Transmission Flushing System In Use.JPG
 

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Discussion Starter #15
Proposal For Methodology For Using The DIY Transmission Flushing System

This is what I have in mind for the methodology for using the proposed DIY Transmission Flushing System.
NOTE THESE STEPS ARE A PROPOSAL ONLY AND ARE FOR COMMENT.
  1. Get the car raised with the trans pan level.
  2. Place trans selector in Neutral with ignition off.
  3. Remove the engine splash panel.
  4. Remove the trans to cooler return line in-line connector and catch the fluid.
  5. Install the flushing system in the trans to cooler return line. Have about 4L of new fluid in the return/new fluid pressure container.
  6. Remove the trans drain plug and catch the fluid.
  7. Dislodge the trans overflow tube and catch the fluid.
  8. Finish removing the pan and catch the extra fluid.
  9. Replace the filter and clean pan, magnets and gasket seat.
  10. Install new overflow tube and pan gasket.
  11. Reinstall pan using new screws torqued to spec. Tighten screws 180 degrees more as per spec.
  12. Measure the quantity of oil removed so far. Will be about 3.5 – 4L.
  13. Install filling adapter and add 1L more new fluid than what was removed.
  14. Start the vehicle engine and observe the discharge of old fluid into the flushing system old/dirty fluid pressure container. The discharge rate will be approximately 1L per 15 secs.
  15. With foot on brake, shift through "P-R-N-D" several times.
  16. When the colour of the discharge fluid appears clean or when the 4L of new fluid is nearly all consumed, stop the vehicle engine. It may be necessary to add more clean fluid and repeat until the discharged fluid is clean.
  17. Remove the flushing system.
  18. Connect battery charger to car battery
  19. Connect STAR Diagnosis Assistance System to OBDII connector.
  20. Using STAR, monitor trans fluid temperature.
  21. Restart car engine and allow to idle in Park.
  22. When the fluid temperature is exactly 45C stop the engine.
  23. Remove the adapter filler.
  24. Observe the quality of the fluid discharging from the drain plug aperture.
  25. When only a small quantity of fluid dribbles out, reinstall the pan drain plug with a new crush washer.
  26. If no fluid was discharged when the trans fluid temp reached the 45C mark, then add more fluid and repeat the last few steps.
  27. Clean any excess fluid off of pan and drain plug and reinstall underskirts etc.
NOTE THESE STEPS ARE A PROPOSAL ONLY AND ARE FOR COMMENT.
 

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A. No i cannot comfirm the flow of your trans but on the 722.6 the return is on the drivers side.
B. 2 thoughts on this one, first change the filter and the refill and flush with an extra 1l over normal amount so if it holds 9L total 4l in the torque converter about 4l in the tranny and 1l in the cooler and lines. Use 4l with the filter change then 6l to flush. Second thought do filter change then flush till clean fluid flows out the return pipe.
C. I used about 10.5l total used second method above.
D. have a second person to start and stop the motor as you watch the system while flushing is a better option IMHO.
E. I'll have to look into that one for you.

Dean
 

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Brian just a note for you the setup I used didn't work as planned. I will be adding a 1 way check valve to it so I can pressurize the bottles before starting the motor next time I use it. I think the air was compressed in the process last time.

Remember the fluid needs to remain at 40C when you are adding it to the tranny. see attached.

Dean
 

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Discussion Starter #18
A. No i cannot comfirm the flow of your trans but on the 722.6 the return is on the drivers side.
Hi Dean, so seeing as you are in Brisbane the driver's side is on the right which is opposite to my assumption.
Looks like I will have to do a test when I have opened up the line. I could start the engine with the flush lines attached and directed into a container and then just see which one spits fluid.

Re Question B. I have purchased 10L of genuine M-B automatic transmission fluid ATF134 sheet 236.14 which costs the earth. I got 1L extra as a spare.
I still think it would be a good idea to start the flush process with something cheaper and when it runs clear add my 10L of M-B Fluid. With your neat system you can see when 10L has been pushed out.

Re Question D. about putting a bypass valve in the flush system. I was worried about my limited quantity of genuine fluid running out before it came clean. With the bypass valve opened it would not let the transmission run low. This wouldn't be a problem if I started with some cheaper fluid.

Thanks again, Brian
 

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Discussion Starter #19
the setup I used didn't work as planned. I will be adding a 1 way check valve to it so I can pressurize the bottles before starting the motor next time I use it. I think the air was compressed in the process last time.
Dean,
Some professional flush systems use a 12V pump to assist the flow through the cooler. I would have thought that considering that pressures as high as 220psi are possible inside the valve body that the existing trans pump wouldn't have any trouble at all in pushing the fluid through the cooler and the two flushing canisters.
If you pressurise the two canisters at the start, won't that make it harder for the trans pump?
Brian
 

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Fuchs oil in mine costs $48 for 4.2L bottle. MB 236.14 - Automatic transmission fluids (ATF, Specification 236.14) - Mercedes-Benz Specifications for Operating Fluids

Yes drivers side is the right.

The bypass valve would allow the old oil to flow through to the transmission pan and continue to go through the system again as well as the filter. If you wish to used cheaper oil I would get 2 filters, even then you will need to flush the cheaper fluid out after you used it to flush the system. Turning the key off is a better option to me, stops the flow straight away.

Dean
 
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