Mercedes-Benz Forum banner

My attempt at replacing the transmission plug.

167K views 158 replies 55 participants last post by  MBGraham 
#1 ·
This afternoon I went ahead and changed out my transmission harness plug/ connector, the how to's that are around for this are pretty good but I was still not sure going into it how to remove it so I decided to snap some pics of the process.

What the underside looked like, when I first jacked up the front end.


Pull down the wire connector (fastened with a clip) to reveal the screw that holds the shield in place.


There's a star pattern screw hidden away under that harness that I just pulled out of the way, unscrew it.


Once the bottom screw is removed, simply push the thin metal shield out of the way revealing the connector.


Better look at the connector.


Twist the plastic white tab towards the bottom as the arrow indicates. The twist motion pushes out the wire harness connector.


Once its released, pull it out the rest of the way, out of the way.


This is where the problem comes from... the oil leaking into the wires, as you can see its drenched in oil.


There is a 7mm bolt in the center of the connector where the arrow is pointed.


7mm setup to unscrew the bolt.


This will allow you to pull the connector assembly out, this is i the part you'll be replacing. Closer look at the connector you'll realize that you did not have to purchase the whole connector, rather just the two o-rings that go bad over time. The connector only cost $15 from the MB dealer, the o-rings would've been $1-$2, so not a huge savings there either. The o-rings I'm referring to are pointed out by the red arrows.


Once you pull out the connector, this is what you should end up with.


The old and the new connector.


The new connector in place, with the 7mm bolt tightened.


From then on, just work backwards. The whole process took less then 30 minutes. In my situation the transmission fluid is very dark and will be replaced here very soon.

Kruso
 
See less See more
14
#110 ·
Oops, capacitor fell off

Had oil in my TCM and was cleaning it up when the capacitor fell off. Probably a cold solder joint. I was able to repair it since I have a pretty good Weller iron with a fine tip, but in hind site, I probably should of just drained the box overnight and re-installed.

My TCM is quite a bit different with surface mount devices (even the capacitor) and a sheild over some chips.
 

Attachments

#113 ·
Thanks for these two explanations. Mercedes Benz South Africa has just quoted me the equivalent of USD 5800 to replace the TCM and the wiring harness. Total rip off!!!
So I will be taking the car to my non-franchised service man and asking him to replace the O rings and to clean out the TCM with electro spray cleaner. I worked for Detroit Diesel Allison 25 years ago and we had this same problem with oil percolating into harnesses of the early electronic transmissions. We solved it by using the correct oil proof connectors. So why can't Benz solve a problem like this. I'm actually very disappointed with the W210 reliability as I've just had an ignition lock failure and a transmission electrical control board failure on the two cars we have [total repair cost USD 2300]. Between my wife and I we've driven a W115, W123 and W126 over the last 25 years and clocked up over a million kilometres on these three cars with nothing like the repair costs of the W210.
 
#114 ·
I don't know if that was your bad luck, or letting mechanics rip you off, but I don't consider need for $8 adapter every 10 years a reliability issue.
More like not keeping up with maintenance updates, as this is the item the MB posted in the updates several years ago.
That said, wife W210 in 8 years of ownership cost us about $124 a year in needed parts and some of that (crack radiator) I blame on PO hitting a curb.
Still not bad for a car with over 250k miles on the clock.
 
#115 ·
All of these experiences and expenses are relative, varies person to person, region to region and the specific vehicle.

I just pulled my records after reading you and Kajtek, I own this car since May 2011 and from May 2011 to July 2012 I put maybe 5K miles on it until I started a new job in July 12 and started to drive more than 40 miles one way to work, 5 days a week.
From May 11 to July 12, the first year, I spent $59 for the parts and that was the antenna cover, wiper blades, air filter, light bulbs etc.
Since July 2012, I gradually spent about a total of $1200 for the parts, that includes, complete rear brakes, motor mounts, tranny mount, front bearings, fuel filter, spark plugs, wires, rear window regulator, ATF,filter gasket, idle pulley, belt tensioner, flex discs, center bearing, tranny pilot bushing, sway bar bushings, sway bar links, etc etc.
As you see in the list, all of these items are wear items; 11 years for flex discs is normal IMO, 12 years for sway bar bushings and links is absolutely acceptable.
Nothing broke down on this car during my ownership(except the rear window regulator) and I never got stranded anywhere, all of the above items I bought and changed myself because I believe in preventive maintenance. When buying this car I knew I was buying a 10 years old car even with the low mileage it is more than likely all those rubber and wear items will need some attention sometimes, I spend little here and little there, every month address a different potential issue and keep enjoying the smooth ride. I know you don`t maybe get the same feeling as the W126 or W123 in these cars anymore but still W210 is a good reliable Benz among all other weird stuff out there.
Good luck and enjoy your ride.
 
#116 · (Edited)
Just to clarify- I don't consider fluids and wearable as repairs.
Rotors, wipers, filters all go with fuel cost as operating cost.
Broken radiator or water pump is not something you can predict, so this is definitely repair.
Transmission adapter? I would add it to operating cost, but it might be a judgment call. Still since I paid $6 for mine and DIY >>> not a big deal.
How do we qualify alternator brushes? Since you can't buy them alone, it makes about $50 for voltage regulator, or about $800 when you take it to a shop and get talked into new alternator.
In another words, how do you qualify your lack of doing your homework? ;)
It is only human afterall.
 
#117 ·
Absolutely Kajtek, those were my points, like I said there was no way to predict a broken window regulator and sorry I'm not gonna open my door covers to check condition on them, alternator brushes on the other hand always in my check list since you always advocate to give them the first shot before spending the big money on any R/R job. Matter of fact I saved a friend big bucks in August with your advice, he checked them first and sure thing they were bad, got the brushes and changed them a Sunday, shop quoted him more than $400 for his Saturn.
 
#118 ·
2nd hand Benzes have always been really good value for money and are safe great cars to drive.
However the electronic gremlins are starting to surface on these older cars and because of the level of electronic complexity require dealer intervention.

I have always maintained and serviced my own Benzes or used a trusted non franchised dealer I have known for years but even he is at a loss on these electronic problems and that means the dealer has to fix them according to Benz policy and warranty.

I live in South Africa and I travel regularly to remote places. A dealer may be 3 or 4 hours away by road. So if I have an electronic failure in one of these remote places it is likely to be a very expensive flat bed journey to the dealer plus extra travel and accomodation costs. This is why I make the comment about reliability and running costs as these cars can't be sorted out by either me or the country garage any more unless it's a simple mechanical problem.

Cheers
 
#119 ·
Thanks for the helpful thread. Did this job today on my E55. Not very hard, but had to replace 13 pin plug holder and take apart my TCM to clean out trans fluid. My guess is I saved $600 to $800 by saving a trip to the dealer. All back and working well. No leaks:thumbsup:
 
#120 ·
My tale of troubles with our E320 continues. It has blown the torque converter seal because the primary pump front bushing seized and then pushed out through the torque converter seal. This happened at the dealer after the dealer had fixed a minor oil leak on the box. My opinion is that someone started up the engine when the box was drained. Dealer asserts other wise. So this is not going to end in a nice way.
Has anyone got any history of failures of the front bushing and primary oil pump. I see the replacement pump now has a needle roller bearing not a bushing.

Cheers
 
#121 ·
very nice write up and a long long thread to follow.
I'm in the process of changing this plug because, after my inspection I found it was flooded with oil but not the ECU. the reason I'm doing this is that when cranking the car and the ignition key inside, the display doesn't show the gear I'm in, i.e. PW. After several trial of rotating the ignition key the gear is displayed and the car is working now properly.

do you think by doing this i will have my problem solved or there is other problem i should look into? thanks in advance.
 
#122 ·
Usually that's related to the shifter module (in the center console) but obviously you need to change the pilot bushing anyway. If that fixes it, then consider yourself lucky. ;)

Speaking of which, Good luck. :D
 
#123 · (Edited)
HI,
it been a few months since this problem occurred but here's what we did.
1.0 We replaced the plug and the O rings. The O rings seem to be a weak point on this transmission as I managed to get the dealer service history of both cars and this failure seems to occur every 50 000 to 60 000km.
2.0 Now having done that the next most important step is to see how much oil has wicked its way up the transmission harness into the transmission control module.
3.0 Disconnect the TCM plug in the control box under the hood and clean it out and also wash any oil off the wiring harness with "Electroclean' or some other electronic solvent cleaner. Don't use anything aggressive like aerosol carburetor cleaner or any water based detergents. In the worst case pure isopropyl alcohol will also do.
4.0 Now lift out the complete TCM from the control box and turn it upside down. Leave it like that for a while to see if any oil has collected in the casing. The TCM is NOT a sealed module and oil leaking into the plug from the wiring harness will percolate down inside the casing. If in any doubt leave it upside down to drain for a night.
5.0 Reassemble and make sure that the TCM plug seats correctly and clips tight. Close up the control box.

Unfortunately it is a fact of life that the capillary action of oil will allow it to creep up any wiring harness over time. The only way to stop this is by creating a physical barrier like the transmission plug or to have a bulkhead plug that actually breaks the harness. The oil travels two ways, either up the inside of the individual wires between the insulation and the conductor or it uses the harness sheath as a wick.

So I've added this little check and cleaning exercise to my regular maintenance checks both our W210s. In our case there was about a dessert spoon of transmission oil that had collected in the bottom of the TCM housing of the one car.

Regards

John
 
#124 ·
I need to ask some questions that were not clearly answered before.

Does the oil in the TCM affect the normal operation of the transmission mechanically and electronically?

Does cleaning the TCM with a towel is enough and guaranteed to have a pleasant result?

Does the oil in cables linking the transmission to the TCM affect the speed of signal transmitting between the 2 mentioned items.

Has anyone stopped the capillary effect of oil going up to the TCM?

Thank you guys for your support! :thumbsup::thumbsup::thumbsup:
 
#125 ·
My attempt at replacing the plug on W210 tranmissions

In reply to the questions asked:-

Oil on the TCM eventually breaks down the insulation of the components and cause them to short out. It also damages the PC boards and causes them to short.

Cleaning the TCM with a cloth or paper towel will not remove all the oil. There is also the danger of hooking one of the small components with the cloth threads and breaking off the connections. The best way to clean the board is with a non aggressive solvent cleaner such as "Electroclean". This cleaner is available in an aerosol spray can from any good hardware store or electronics supplier and allows one to "spray clean" the board without any physical contact with the board.

Oil will not change the TCM operation unless it has caused a breakdown of the electronic component insulation or the PC board insulation. Then there will be an error signal of some sort which could affect the transmission mechanically or electrically. The biggest danger here is from an intermittent electrical signal that causes clutch slippage.

Oil can't affect the speed of electrical signaling.

If you can find a way to stop the capillary effect you will be a very wealthy man. The standard fix on some harnesses is to cut the wrapping and have a small exposed area where the oil is supposed to drip off the wires . Frankly I'm very dubious of this fix.

Automatic transmission fluids especially these synthetic fluids used today are very aggressive to human skin, certain paints and some plastic components as well. This fluid should be handled with care. Contact with skin, paint work or plastic components should be minimized or avoided.

Hope this answers your questions

Regards
John
 
#126 ·
In reply to the questions asked:-

Oil on the TCM eventually breaks down the insulation of the components and cause them to short out. It also damages the PC boards and causes them to short.

Cleaning the TCM with a cloth or paper towel will not remove all the oil. There is also the danger of hooking one of the small components with the cloth threads and breaking off the connections. The best way to clean the board is with a non aggressive solvent cleaner such as "Electroclean". This cleaner is available in an aerosol spray can from any good hardware store or electronics supplier and allows one to "spray clean" the board without any physical contact with the board.

Oil will not change the TCM operation unless it has caused a breakdown of the electronic component insulation or the PC board insulation. Then there will be an error signal of some sort which could affect the transmission mechanically or electrically. The biggest danger here is from an intermittent electrical signal that causes clutch slippage.

Oil can't affect the speed of electrical signaling.

If you can find a way to stop the capillary effect you will be a very wealthy man. The standard fix on some harnesses is to cut the wrapping and have a small exposed area where the oil is supposed to drip off the wires . Frankly I'm very dubious of this fix.

Automatic transmission fluids especially these synthetic fluids used today are very aggressive to human skin, certain paints and some plastic components as well. This fluid should be handled with care. Contact with skin, paint work or plastic components should be minimized or avoided.

Hope this answers your questions

Regards
John
Thank you John for your replies. Very detailed and informative:thumbsup:
 
#127 ·
I'm always glad to check in on this thread, everyone is so pleasant here. I've been a part of dozens of online automotive forums (several for over a decade) and this community is the nicest I've come across thus far. I'll hopefully be back here full time, planning on purchasing the new S350 in the next 2-3 years (very turned on by diesel mpg potentials).
 
#130 ·
If you are asking how to measure the oil level at 80 degrees Centigrade [that is engine close to running temperature] proceed as follows:-

You will need a flexible measuring dipstick as Merc don't supply one for the W210.

They are available as a service tool from El Paso Tools in Texas and may be from some of the better parts and accessory stores in the USA. Merc generally don't sell this tool over the parts counter.

Other wise like me you can make one from a piece of 3/32" inch diameter stranded steel cable available form any hardware store. You will need about four feet of cable. Don't use 1/16" cable as it is too flexible.

Braze or weld up both ends to stop the wire strands unraveling and cutting hands and grind the weld/braze smooth and round so it can't get hooked on anything. One end helps to guide the cable down the filler tube like a fish tape or fish wire and the other end is for you to hold onto.
Don't use an electrician's fish wire as it is too wide and too stiff to go around the small radius bends.

Now park the car on level ground, with the engine idling and gently push the cable down the filler tube until you feel a solid resistance as the end of the cable touches the bottom of the oil pan. Don't force it further as the cable will deflect along the bottom of the oil pan and damage the oil filter.
This is also why you must NOT use a very soft flexible cable.

Withdraw the cable carefully and measure off the "wet length" . It is quite difficult to read as the transmission fluid is clear in colour and you may need several attempts to get a decent reading. I found that painting the end of the cable with matt black enamel paint made it easier to read.


For the W210 the "wet length" should be around 62 to 65 mm with the transmission oil at engine running temperature and the car parked on level ground.

The advantage of the El Paso tool is that the "wetted end" is specially marked and is easier to read than a stranded steel cable

Remember that this transmission uses a Mercedes spec synthetic fluid and not the normal Dexron type available from parts stores.

Hope this helps.

Regards

John
 
#140 · (Edited)
Take the car for at least 20klm drive,not on the highway,but in an area where the car changes gears frequently. This will warm the fluid to normal operating temp. of 80 degrees celcius. Then measure the fluid level with the engine running.
Presuming you are not driving in sub zero conditions,this will work fine for everyone who does not have a infra red thermometer.
The transfluid cooler is also a heat exchanger,therefore it warms transmission fluid when colder than the engine coolant,and cools trans fluid when it is hotter than coolant. Provided you drive for enough time for everything to reach normal operating temps,then stop and measure the level as per the correct procedure,you will be fine. I have set my fluid level this way many times on three different cars with great success.
The fluid level must be correct when the engine and transmission have reached their correct operating temps,that is all that matters.
Those using thermometers getting strange readings may need to check the accuracy of their thermometers.
 
#134 ·
I'm not quite sure why people continue to trot out the "drive for x miles in this way" stuff.

Assuming that the goal is to get the fluid to 80c, and further assuming that fluid temp is directly related to fluid level, then at best such recommendations are only an approximation. You might be high, you might be low...who knows?

Once you have set the 25c level, do a test drive, then let it idle. Check the temp after the fan kicks off. If it's so cold that the temp won't rise, block the radiator, in stages.

Good luck.
 
#136 ·
Where do you point the thermometer and what is outdoor temperature?
I deal with infra-red quite a bit and they are very sensitive to dirt, paint and other things on the surface.
That said, for me checking the level after some drive is easier than sit and wait at the idling car, but everybody has different life style.
Another thing is that common knowledge is that transmissions don't have thermostat, however I measure few times they hold pretty consistent 80C
 
Top