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126 transmission oil/filter change

Started by nathan, 28 June 2008, 09:26 AM


hi all,
so, following in my previous posts of attempting ridiculously simple tasks for anyone else but me, i attempted to change the transmission oil and filter on the 126 500 today...

i bought a replacement mann filter from lintrex for 30 bucks, the gasket was 20 bucks.  i searched the web and figured out the basics. for anyone that doesnt know much about such a task, here is my simple understanding.  there is about 7-8L trans fluid in the unit.  ~ 3L is kept in the torque converter and the rest in the pan which is easily accessed.  there are valves which prevent the torque converter oil simply draining into the pan when the engine is off, so you cant just drain the pan and get all the 7-8L out, you must drain both the torque converter and pan separately.  problem is, access to the TC is a bit of a bitch.  the drain plug is accessible through the 'mesh' but as the TC spins, it isnt visible all the time.  to get it to spin to the mesh to undo it, you must turn the engine over which you can do one of two ways
i)spin the ring gear with a screwdriver where accessible (on the 126 you can see it directly at the bottom, or undo the 2x10mm bolts on the front end of the bell housing and remove the small metal plate and you can see the ring gearvery easily
ii)manually crank the engine by removing the fan, then putting a 27mm socket over the crankpulley bolt and rotating clockwise, checking where the drain is now at, and repeating until you see it (this is time consuming by yourself!!)...this is how i did it as it seemed the most referenced way

draining the pan is simple, simply undo the 6mm allen bolt at the base of the pan and let it all drain out...then undo the 6 13mm bolts around it and drop the pan (prepare to get this crap in yourhair!) prior to cleaning it...then you can see the filter (the rectangular thing) in the trans itself, which has 3 phillips screws retaining it.  my filter had a lot of crap in it, and 'sludge' on the top but i didnt see metal flakes per se.  i cant believe many cars dont have drain plugs on the pans and TCs, this would make the task even messier and harder!

draining the torque converter was hard without the appropriate tools.  in the end i failed...although i have massive biceps (as somalians go), i couldnt undo the thing with a piss weak 10cm long allen key...i think the head of the allen bolt was 5-6mm...TIM OR PB, do either of you have a ratchet attachment i can borrow to try this tomorrow??

i am aware not to use sealant on the gasket/seal for the pan and that absolutely no grime must get into the trans.
not that im there yet, but refilling the 126 trans is supposedly with dextron III 'oel'...i imagine it must take forever to put 8L down that tiny dipstick. 

attached are some pics of the task sure it will get quicker next time!!
you can see the dirty oel, which shuold be red! even a colour blind fool like me knows the current crap must have been in there a while!
regards and please drop me hints
pic 1 pan
pic 2 pan off with filter on right side of pic
pic 3 old filter
pic 4 crank pulley - rotate it clockwise with 27mm socket. you can see the radiator at base of pic
pic 5 the TC drain plug visible between the pan and a cross member support (what is this thing, if i pull it off will the car collapse?! ;))...access is better but still crap once the pan is off

1979 116 6.9 #6436
2018 213 e63
2011 212 e63
2011 463 g55
2007 211 e500 wagen
1995 124 e320 cabriolet
1983 460 300gd
1981 123 280te


Great post Nathan!!

You've just solved a great mystery for me an my mechanic.  Each time we've had the car on the hoist and done the tranny service, we put on the new filter / gasket and then proceed to top up the tranny fluid.  Each time we think we've only put about 3-4L in it says it's well over full.  I had NO idea (and my mechanic/mate doesn't usually service merc's) that you had to drain the TC seperately?!!!  ???

So just to confirm this, it would be the same on a 450 / m117 right?  ???

Did you end up having to turn the crank manually to get the drain plug visible?  And did you remove any other covers to see the drain plug at all?

Cam.  :)


Hi Cam,
interesting about your mechanic mate who doesnt work on mercs not knowing about this. i believe its the same as the 450 m117, but not positive - one of the others would have to confirm this. as i noted, two ways to visualise the TC (does this acronym remind anyone of Magnum PI btw??)...the one i chose which seems to be the appropriate way is to crank the engine manually with a not sure why, but internet writings say only crank it clockwise, never anti clockwise (why??)...i did it in 0 to one quarter circle turns of the ratchet and then checked imder the car to see where the TC drain took about 5 tims to eventually find it. no other covers are necessary to visualise the drain...keep in mind though you need to remove the engine fan (4 x 10mm bolts) to get access to the crank pulley (/harmonic balancer??) to turn it.
ill let you know if i get it out tomorrow but im dead set on changing all oel!
1979 116 6.9 #6436
2018 213 e63
2011 212 e63
2011 463 g55
2007 211 e500 wagen
1995 124 e320 cabriolet
1983 460 300gd
1981 123 280te

TJ 450

Whoa... that is one dirty filter :o.
Awesome pics!
I would expect it to behave a lot better after the change. Unless that muck got through a dodgy seal or the dipstick, it's come from the guts of the transmission somewhere.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


Yes Cam you drain the torque converter on a 116/117/100 auto the same way.

Yes Nathan - I don't like what is on that filter. Is it attracted to a magnet and hence bearing particles or is it sludge from friction material. Either way I would worry about the health of the transmission without a rebuild.

Maybe the source of your surge if it is a bearing gone.




s class

Yep Nathan, that tranny and filter looks more like my W140's than the 116's.  TJ, yes this is the normal procedure for all benz autos - even the 280SE  ;).  Indeed, you will struggle without a allen drive fitting on your ratchet.  You really need to get yourself a set to work on the newer benzes (126 and on) where allen bolts abound.  A basic 3/8" drive set covering 5mm to 12mm is not expensive.  I prefer 3/8" over 1/2" drive for allen sockets, as they are more compact.  Allen head bolts are often used in tight spaces, so compacness of the tools is helpful.  A slightly related comment - my W140 is so cramped in the engine bay, that I basically never use my standard 1/2" drive stuff on the car.  Only 3/8".

There is a third place you should drain oil - from the tranny cooler at the bottom of the radiator.  THis is less critical as it holds only about 500ml. 

I must also voice my concern though about that sludge - likely from wear in clutches or bands.  Sorry. 

[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL