Having recently just purchased my first R230 a ’03 SL500, I have now finished one of my last maintenance tasks of flushing the transmission fluid. Having already accomplished replacing spark plugs, air filters, oil and filter change, diff fluid change, serpentine belt, idler pulley, belt tensioner, wiper blades, DS lumbar support, antenna mast, ABC fluid flush, steering rack flush, cabin filters and pulsation damper. (Still left to do are all three Motor Mounts but I will wait until spring).
I really had not planned to do the flush until spring. I had canceled the insurance, moved the car into a spot in my garage, put a float charger on the rear battery and covered it. It sat for two weeks when I decided to move it to the very rear of the garage so that if I had to work on my W220 I would have room, (my garage is “L” shaped with two car space in the back, two car space in the front and a work space in between). So when I fired it up to move it, there was a small puddle of Trans fluid under it.
I moved it to the back, jacked it up and placed it onto jack stands. I crawled under it and removed the belly cover. Right away I saw that the Trans adapter plug was leaking and the source of my puddle. There was no apparent leak before parking it. I guess every leak starts with the first drip, (old Chinese proverb)?
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I went to my local MB dealership and purchased the Adapter Plug along with a gasket and filter kit for the Trans. If I had more time, I could have saved some money and ordered my parts but the dealer had what I needed in stock so it was worth it not to wait this time.
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I changed out the Adapter plug fairly easily as I had done this before on my W220. You have to remember to lube the “o” rings and keep pushing the plug into the bore firmly until the center screw finally can get a few threads started. At that point, you can draw it in slowly and carefully with your socket on the screw watching your progress and finally just barely tightening it (2.5nm) at the end when it is fully seated.
I have to add, before reassembling the plug, clean up the wires leading up to the TCM. I sprayed them off with cleaner and used compressed air to dry them. There was some oil on them but hopefully the oil has not wicked its way too far up the harness. The car was shifting fine before so any change I will know where to begin troubleshooting.
When it came time to remove the Trans drain plug to drain the fluid and drop the pan, the drain plug torx striped. (Poor design, 20nm seems a lot for such a small torx. (Perhaps the filled for life theory and rarely if ever having to be removed?) I had to drop the pan with it full of oil. One can tilt it to get some of the oil out but needless to say still very messy.
The oil was pretty dirty and the magnet was coated. I was especially amazed at the amount of sludge and gunk on the bottom of the pan. (My W220 was not nearly as bad as this one was). I cleaned the pan and magnet then drilled a hole in the drain plug and used an easyout to remove it.
![Image]()
The new plug design has a much smaller head area with far less surface but still spec says to be tightened to 20nm.
I installed the new filter, new pan gasket and lifted the pan into place then reinstalled the clamps (sprags) and torqued the screws to 8nm.
Next, pull the air cleaner/engine cover off to gain access to the Transmission filler tube. As you can see, mine had never been tampered with……..
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Break the red tab off and push the lock out the bottom then remove the tube cap. Be careful to look for and remove the o-ring which may still be in the tube. Mine turned sideways and if I had not noticed it, I may have pushed it down into the tube with the funnel.
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Next, install a funnel to pour the fluid into the Trans. In my case, I did not have one large funnel with a small spout on it to go into the fill tube so I used one small funnel with another larger one inserted inside to give me a bigger target and room to pour.
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The tube just to the left of the funnel and touching it is an engine oil dipstick access tube. It has a removable plug in it. Obviously, a dipstick was not factory provided.
I then installed 5 Liters of fluid,( per the WIS instruction) out of the 14 purchased from Pelican. This is the initial first fill.
![Image]()
Next was the prep for the actual WIS flushing procedure. The instruction says to connect a fitting to the Trans inlet line then run a line to a bucket.
Fitting seen here………..
![Image]()
And here……..
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This fitting is way up on the side of the Trans above the Catalytic Converter and it seemed to me to be far easier to just connect to the Trans outlet line which attaches to the oil cooler in the radiator than to hook it up under the car. The only downside to connecting at the radiator is that you are not flushing the radiator cooler out. How much fluid is actually in the cooler, who knows? Being aware of this, what I did was lightly blow air into the cooler hoping to push the oil through to the Trans before starting the flush procedure.
Trans cooler line layout…………
![Image]()
Cont’d in next post………………..
I really had not planned to do the flush until spring. I had canceled the insurance, moved the car into a spot in my garage, put a float charger on the rear battery and covered it. It sat for two weeks when I decided to move it to the very rear of the garage so that if I had to work on my W220 I would have room, (my garage is “L” shaped with two car space in the back, two car space in the front and a work space in between). So when I fired it up to move it, there was a small puddle of Trans fluid under it.
I moved it to the back, jacked it up and placed it onto jack stands. I crawled under it and removed the belly cover. Right away I saw that the Trans adapter plug was leaking and the source of my puddle. There was no apparent leak before parking it. I guess every leak starts with the first drip, (old Chinese proverb)?
I went to my local MB dealership and purchased the Adapter Plug along with a gasket and filter kit for the Trans. If I had more time, I could have saved some money and ordered my parts but the dealer had what I needed in stock so it was worth it not to wait this time.
I changed out the Adapter plug fairly easily as I had done this before on my W220. You have to remember to lube the “o” rings and keep pushing the plug into the bore firmly until the center screw finally can get a few threads started. At that point, you can draw it in slowly and carefully with your socket on the screw watching your progress and finally just barely tightening it (2.5nm) at the end when it is fully seated.
I have to add, before reassembling the plug, clean up the wires leading up to the TCM. I sprayed them off with cleaner and used compressed air to dry them. There was some oil on them but hopefully the oil has not wicked its way too far up the harness. The car was shifting fine before so any change I will know where to begin troubleshooting.
When it came time to remove the Trans drain plug to drain the fluid and drop the pan, the drain plug torx striped. (Poor design, 20nm seems a lot for such a small torx. (Perhaps the filled for life theory and rarely if ever having to be removed?) I had to drop the pan with it full of oil. One can tilt it to get some of the oil out but needless to say still very messy.
The oil was pretty dirty and the magnet was coated. I was especially amazed at the amount of sludge and gunk on the bottom of the pan. (My W220 was not nearly as bad as this one was). I cleaned the pan and magnet then drilled a hole in the drain plug and used an easyout to remove it.
The new plug design has a much smaller head area with far less surface but still spec says to be tightened to 20nm.
I installed the new filter, new pan gasket and lifted the pan into place then reinstalled the clamps (sprags) and torqued the screws to 8nm.
Next, pull the air cleaner/engine cover off to gain access to the Transmission filler tube. As you can see, mine had never been tampered with……..
Break the red tab off and push the lock out the bottom then remove the tube cap. Be careful to look for and remove the o-ring which may still be in the tube. Mine turned sideways and if I had not noticed it, I may have pushed it down into the tube with the funnel.
Next, install a funnel to pour the fluid into the Trans. In my case, I did not have one large funnel with a small spout on it to go into the fill tube so I used one small funnel with another larger one inserted inside to give me a bigger target and room to pour.
The tube just to the left of the funnel and touching it is an engine oil dipstick access tube. It has a removable plug in it. Obviously, a dipstick was not factory provided.
I then installed 5 Liters of fluid,( per the WIS instruction) out of the 14 purchased from Pelican. This is the initial first fill.
Next was the prep for the actual WIS flushing procedure. The instruction says to connect a fitting to the Trans inlet line then run a line to a bucket.
Fitting seen here………..
And here……..
This fitting is way up on the side of the Trans above the Catalytic Converter and it seemed to me to be far easier to just connect to the Trans outlet line which attaches to the oil cooler in the radiator than to hook it up under the car. The only downside to connecting at the radiator is that you are not flushing the radiator cooler out. How much fluid is actually in the cooler, who knows? Being aware of this, what I did was lightly blow air into the cooler hoping to push the oil through to the Trans before starting the flush procedure.
Trans cooler line layout…………
Cont’d in next post………………..
