7G gearbox fluid change

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stevieno12000

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Joined
Sep 28, 2011
Messages
50
Location
Glasgow
Car
W211 E280cdi, BMW 118d
I know this has been covered a few times but I really can't find a definitive answer.
I have a W211 E280 cdi pre-facelift (SBC model) but with the new engine and gearbox (OM642 and 7G box). I know it's a fairly rare combination and Mercedes were still using the "sealed for life" philosophy for the auto box.
I had everything prepared to change the transmission fluid but I could not find the torque converter drain plug. I rotated the engine several times and then resorted to taking a slow motion video of the torque converter when the engine was running. I can confirm with absolute certainty that my car does not have a torque converter drain plug.
My question is this. How can I remove all of the fluid from the system, including the TC (as Merc now advise).
Is anyone aware if Mercedes issued a bulletin instructing their technicians how to fully drain the fluid without a TC drain plug?
My car has reached 199k miles and has a massive main dealer and specialist service history but sadly has no confirmed gearbox fluid change. This is why I'm very keen to make sure I drain the full amount.
Any help would be greatly appreciated.

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My first thought would be to do as Olly describes for the 5G box, drain the torque converter by removing the banjo bolt connection to the oil cooler lines and spin the engine to drive out the atf

Unfortunately the images have gone but you should get the idea from his text

How to change the automatic gerbox oil and flush on a 722.6 'box
 
As far as I am aware there's a universal method that involved disconnecting the oil pipes from the oil cooler (located near the radiator) then with the engine idling feeding the transmission fresh fluid into one pipe while collecting the old fluid from the other. I'll see if I can find it online... there may also be a proper MB WIS document for this. Alternatively.... two ATF replacement in quick succession with a short drive in between will rid the box of most of the old ATF.
 
Something along these lines:

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As far as I am aware there's a universal method that involved disconnecting the oil pipes from the oil cooler (located near the radiator) then with the engine idling feeding the transmission fresh fluid into one pipe while collecting the old fluid from the other. I'll see if I can find it online... there may also be a proper MB WIS document for this. Alternatively.... two ATF replacement in quick succession with a short drive in between will rid the box of most of the old ATF.
My very first thought was to do a further change in quick succession. I already have 10 litres of fluid so all I'd need is another filter, alu screws and gasket. Not the end of the world.
The only thing I'd worry about if I were to flush through the cooler is introducing too much air into the system.
Even if I had a TC drain plug that wouldn't drain everything from the cooling system.
Maybe I'll drop the pan and see what condition the fluid is in before deciding what route to go down.
Thanks for your help.

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My very first thought was to do a further change in quick succession. I already have 10 litres of fluid so all I'd need is another filter, alu screws and gasket. Not the end of the world.
The only thing I'd worry about if I were to flush through the cooler is introducing too much air into the system.
Even if I had a TC drain plug that wouldn't drain everything from the cooling system.
Maybe I'll drop the pan and see what condition the fluid is in before deciding what route to go down.
Thanks for your help.
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Two flushes with a good run in between is definitely an option, not much of the old ATF will remain in the system.
 
Two flushes with a good run in between is definitely an option, not much of the old ATF will remain in the system.
Funny timing in your reply. This is exactly what I am doing this evening and tomorrow. I assume 1 day worth of driving (50ish miles) will suffice? I have my 2 sets of fluid, filters, screws etc.
I'll post how it goes.

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After 2 nights of changing the gearbox fluid I can report a few of my findings and tips. I completed the job within 2hrs each time. I managed this at the height of my drive on car ramps, this was too low imho. Without a TC drain plug I managed to drain and refill approx 5.5 litres.
1. Get the car as high and as level as you possibly can. Spend time doing this.
2. Large drain pans are recommended, this is a very messy job.
3. You absolutely need a torque wrench that can measure the 4NM required to tighten the aluminium sump bolts. Do not guess!
4. It's important to pump in more fluid than was drained. The sump will not take this full amount until the engine is started.
5. You also need a way to check the fluid temp. It must be 45 deg C for the level to be correct. It can take quite some time to get there.
6. Don't be scared to tackle this job. If you've got a fair mechanical understanding and ability and the correct tools it's easily acheivable.
Next up my oil cooler seals. Joy.

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