So, I decided to install the AUX in line... pulled back the carpeting, and what do I see? Oil on thee bottom of the passenger seat pan... I'm so distressed.... I mean, there was about 2 tablespoons worth... at least... and its all over the wiring on that side of the car.

Since reading so many excellent posts on this forum, it dawned on me... is this the wicking from the tranny sensor to TCU problem? I removed the panel for the TCU, and sure enough, the oil is coming from that plug, down the line and empyting on the bottom floor pan.

Yes, there is oil all the way up to the TCU connectors... I pulled one out, and inspected it, but does not seem like there is any oil on any of the contacts.

SOOOoooo... obviously I'll be replacing that plug in the near future... but, what are YOU doing to displace the oil that has wicked up the wires? A degreaser of some sort?? I'm sure we should get rid of the oil that is present on the wires as well as replace that plug... no?

Jason
St. Louis

 

ur not gunna like to hear this but this almost happend to me

your Autotrans plug adapter (under the car)is leaking so much it traveled up the wiring harness and onto your trans computer

i got a quote for this from an indy for about 2 grand for the tcu

my mechanic used brake cleaner to remove the trans oil off the wiring harness

u can try to clean the tcu and get lucky

 

I'm not having any shifting problems at the moment... so that is good. As soon as I get the part, I'm going to pull the TCU out, and apart, and inspect it for oil. Like I said, I don't see any evidence of oil on the contacts of either the male or female side of the connectors. I may be lucky.

Anybody have a part number or referance number I could use to look up the O-ring/bushing/connector assembly? I don't see it listed in AutoAz's website...

 

I just pulled the bottom pans this weekend to replace the thermostat and found this problem. I searched for longer than I care to admit and found lots of posts on this and nobody posted a part #, which I found a little frustrating. I just ordered this stuff from autohausaz:

00004330401 ATF, Automatic Transmission Fluid; Lifetime Synthetic Transmission Fluid; 1 Liter Bottle
1402700091 Transmission Filler Tube; Filler Cap
1402700098 Transmission Filter Kit
1409910055 Transmission Filler Tube; Lock Pin for Filler Cap; Red Plastic
2035400253 Auto Trans Conductor Plate; Adapter Plug with O-Rings

I'm going to do the filter & partial drain/refill along with replacing the plug (per install university). I haven't checked for wicking but guess I really need to do this. I cleaned everything up then went for a short drive and was surprised at the amount of leakage - so much so I'm not going to drive the car until I perform this service.

Oh, I all ready have the dipstick so didn't order that or have the part # for it but you'll need one too.

 

YOU ROCK! Thank you for the info... Even better that now its logged in the forum for ever!!

Soo... the wicking part... what do people use to get rid of that oil in the harness already?

 

The best thing is to replace the harness. Otherwise clean it thoroughly with CRC electrical cleaner or similar. You must keep the oil from reaching the TCU. If it gets into the TCU you also need to use CRC electrical or switch cleaner to get it out before damage can occur.

Good luck

 

Is it okay to just unplug the two connectors from the TCU? Didn't know if there was some special procedure to R and R this component...

 

Fine to unplug as long as the car is powered down & no key in the ignition.

 

Heads up on the ATF part # I listed above - it's the Fuchs 3353 ATF, not the most current Fuchs 4134. I just noticed this and my car is up on stands with the tranny pan drained... I would rather have put in the latest & greatest stuff and thought that's what I had ordered. Stuck now so going to use it, but will go with the 4134 next time (unless they have something better by then).

BTW, the circular loop w/red wires in Glyn's pic above is the wire loom that gets the oil wicking up into it. What saved me is the tie-wrap tying that loop to the mounting plate - the tie-wrap directed the wicking onto the plate/floor instead of up into the TCU.

 

I ordered everything you did... so the Fuchs 3353 is going to be okay??

 

Is that the Auto Trans Conductor plate aka SPEED SENSOR with the valve body. I am running into this problem with my 06. Good thing anything 05 and below, you are able to do this as a DIY, as for mine, it has to go to the shop = $$$.

I am starting to hate the 7G tranny.

Yea, since you are at it, mind as well change out the conductor plate aka speed sensor, which will put you in limp mode one of these days.

 

No - This is the 5 speed transmission we are talking about. The TCU is built into the 7G transmission.

 

Benz has now mandated the use of the new 236.14 fluid in the 5 speed.

 

Well, the 3353 is in there now... I looked all over for some 4134 (134) type and none to be found in this small town. I'll tell you what though, I'm impressed with the difference it made. Maybe it was just because I was down on fluid some, but the shifts are smooth as silk now, I dare say better than I've ever felt.

Another thing I was bummed about was that I don't have a magnet in my tranny pan. The tranny was serviced ~40K miles by the dealer for an issue under warranty (they replaced a valve body if I'm not mistaken), so I'm guessing it never got back in at that time.

So yes, Glyn, I guess I'm wondering how 'bad' off I am with the 3353 in there? It's got to be better than the stuff that was in there before (before the 3353 came out), no? Am I ok going another 40K or should I be worried?

 

The 722.6 survived just fine on the old fluid for many years. I would not loose sleep.

The real difference is that the new fluid will maintain smooth shift shock for longer than the old.

I'm just making sure people know the latest Benz recommendation.

 

- Thanks Glyn!

 

Yes, thank you Glyn... This forum is fantastic... on par with the Saab one I also belong to!

 

Boom, your dipstick was shipped Fri. or Thurs I forget.

 

Just a couple notes to follow up on this...

I've all ready put my floor pan back together but was thinking I should have put a rag or some paper towels, judiciously placed, in there with the wire to possibly absorb any oil from further leaks. Since the TCU is suspended on the mounting plate, if the wicking oil is directed to the floor disaster should be averted.

I wound up putting back in 3.4 qts of ATF. I was able to catch 3+ quarts in a pan when I drained and then poured it into an empy gallon water bottle. 3.4 qts. brought it to the middle of the 80 degree zone when the car is up at operating temp. It sure looked like I had lost a bunch more fluid, but apparently not. Since I had 3+ quarts in the container, I started with adding 3 qts and went from there. As mentioned in another thread on this, a little goes a long way here. The .4 quarts brought it from just touching the dipstick to the proper level.

This should be obvious, but... Yes it's a pretty bug mess to drop the tranny pan, so be prepared. Install University's method of dropping the rear of the pan worked very well, but still messy. The obvious part: pull the tranny filter when you drain the pan, don't wait until you're ready to put everything back together as there's still ATF in the filter and it will leak out when you pull it. Having done numerous tranny filters I should have known better...

Not saying this is the best way to go, just what I did: to clean the oil in the harness I used CRC MAF cleaner because it's what I had on hand. Very similar to electronics cleaner but maybe not quite as harsh (safe on wires/plastic/etc.). I sopped up as much as i could with paper towels, then used the CRC and mopped up with towels again. It only took a few minutes before the white paper towels could not find anymore oil.

 

I double checked 2035400253 since the description seemed wrong.
Forunately the PN is correct, but mercedes calls it a Pilot Bushing.
And whie they show the orings, they aren't available except with the plastic piece.

 

Thanks everyone... Going to tackle this project as soon as the dipstick arrives!!

 

I remember when I first bought our C230 and took it in to the Dealer...they told me that they were going to replace the "Pilot Bushing" on my transmission as they are being known for leaking...it should only take a "few minutes"...

I looked at the SA and said, how and how is is leaking? I'll need a loaner for sure, you can not change it in a "few minutes"...He said it was just a little plug connector on the side of the transmission...I said no...that is a pivotal part of my clutch and input shaft. He looked at me funny and said...oh, this is a problem with the automatics...you're fine.

- My point, that term is confusing, pilot busing...

- Another point for the OP, Boom 132 - in a case like this...just log onto http://epc.startekinfo.com and get an account...you can locate all of your parts - and purchase WIS for the OEM Shop data on dismantle and assembly.

Hope everything is a okay in your w203!

 

So with the help of several people on here (you know who you are), I was able to change out the ATF fluid. I calculated 3.1 liters fluid taken out, and had to drop in 3.6 liters to fill completely.

Strange, there was no magnet in my tray... can't believe how bad that fluid looked. Well, I should have done the "flush"... I think I'm just going to run the fluid swapout for a couple of months, and then do the "flush"... hopefully, by that time, I'll have a part number for a magnet.

Anyone have part numbers for the wiring harness to the TCU? I'm going to clean up the wiring harness tomorrow afternoon... Let you know how that works out... Thanks again everyone!

 

Harness part numbers I have: I think all you need is the first one?


50 A 203 540 54 05 WIRING HARNESS
AUTOMATIC TRANSMISSION [107], [108]
Code: 423 001 L

Plus

50 A 203 540 87 35 ELECT. LINE
AUTOMATIC TRANSMISSION [002], [090]
Code: 423 001 L

 

Stealership wanted over $200+ for the harness.. Nix that idea.
I pulled back all the carpet/padding, and removed all the wires/cables in the trough alongside the door and cleaned each and every friggin one with CRC Electrical spray.

I pulled off ALL the oil impregnated fabric ties, which were drenched in fluid, and replace with zip ties. I also opened up the TCU, and thank god, it was bone dry, with no hint of oil anywhere.

I cleaned up everything so well, you could probably eat off the floorpan. So hopefully I have dodged this bullet. I would HIGHLY recommend anyone "thinking" they have this problem, immediately spend a couple of hours cleaning up the mess... you'd never believe how much oil wicks through that harness...

Thank you everyone for your help!