sesquipedalian

Greetings:

I posted this on the W210 forum, but it seems like it's a ghost town over there, and given that this situation is not likely to be completely unique to the W210, I thought posting it here would yield better results.

Original owner of a 2001 E55, here. I just replaced the front upper and lower control arms. If you've ever done this work, you'll know that the upper arms are a pain in the neck to get to (bolts). The passenger side is very messy, as you have to remove the ECU and other modules, etc. During that process I noticed some oil in that box and didn't think much of it. Having left the pieces out for a few days, I noticed after assembly that one of them (not actually sure which one) leaked out a good amount of oil onto the floor. It seems like it's a mineral oil, but I'm not sure.

I hope this isn't a 'doh!' moment for me... I did some searching last night on the interwebs, and I couldn't find anything on this at all. Thoughts or answers as to what this oil is, and where it came from? Thank you.

tw2

Could you please post a picture. Is the TCU in this area? I presume we are talking high up in front of the cowl?

sesquipedalian

Thank you for your response, tw2. This is the only photo I have handy. The white specs you see, which look like tiny pieces of styrofoam, are just the reflection of the light, off of droplets of oil.

There was some oil (very little) at the bottom of this housing. Most of the oil seemed to drip out after the modules were removed. Hope this helps.

tw2

The only thing I can think of is IF the TCU is in that bunch then the fluid can wick along the harness from the transmission through a failing pilot bush. For the w211 the TCU is under the floor mats in the foot well but I don't know the placement on the w210. That is my one and only guess since oil doesn't travel up from anything else in the engine bay.

sesquipedalian

tw2, I believe the TCU is in that box. I searched: "xMercedes Benz TCU W210" and one of the links I found, was this one: https://www.peachparts.com/shopforum...ation-tcu.html. On the same page there's a link to a diagram for the W210 (the resolution isn't great): https://www.peachparts.com/shopforum...m-location.jpg


I don't know (yet) if it's limited to diesels, but it does appear to be a wicking problem from the transmission as you suggested. Nonetheless, it looks like the problem was resolved with a bushing replacement in the 2000 and beyond models, by replacing the bushing with a roller bearing.

Correct me if I'm wrong, as I haven't filled an AT transmission with fluid in many years: the fluid is generally pink/red in color, and certainly it has a distinct odor. This fluid didn't have a noticeable odor, and it was clear - similar to mineral oil.

tw2

They didn't resolve the bushing issue to much later as we all have the same transmission and leaking issue as well. They revised the design several times over the years. It's still a plastic insert with o-rings. Yes pink and stinky...

If you want to check it, unplug the harness at the transmission. If it has been leaking you will get a small puddle of fluid rush out. If you get nothing then it definitely isn't the problem.

sesquipedalian

I will check into that, tw2. Again - thank you. Good information! Hopefully by the end of the week...

sesquipedalian

tw2: how much effort is involved, to get to and unplug the harness on the transmission side? I had asked the shop doing the alignment to take a look, and they said it was more involved. My sense is they forgot or didn't feel like messing with it for some reason. Thank you.

For what it's worth, they also could not tell the type of oil and source...

hachiroku

didn't fully read through but the 722.6 transmission electrical connector/plug tends to go bad and transmission fluid will eventually walk its way up through the harness and could lead to failure of the TCU if it gets too wet.

KAMG

The plug at the transmission is not hard to get to at all. It's right above the trans oil pan. All they need to is to remove the rear section of the under body tray to get to it

sesquipedalian

Good stuff, hachiroku. That seems to be a common issue.

KAMG, thank you for the explanation and photo. I will get underneath and take a look. Appreciate all of the help on this thread. Thank you.

hachiroku

we of the W211 family welcome you with open arms. feel free to join us at some point with adoption of the W211 chassis.

sesquipedalian

Well, thank you, hachiroku! You never know... Maybe a new one...I happened to stop by the dealer and saw a nice black on black E63 (chassis W???) in the showroom. It's quite an improvement over the W210.

tw2

Its very easy, the plug has a tab you turn to unlock it and it pulls out. Might as well install a replacement bush at the same time. They are extremely cheap for once.

Pmarino

sesquipedalian

Great. Thank you. I will check online for the part, and order it. Appreciate the advice.

sesquipedalian

Thanks for the video, Pmarino. That is helpful. So the issue, and what tw2 referenced as a less expensive bushing, is an o-ring problem. Seems odd that they were more expensive.

The trans fluid was changed out a few years ago, so I see the need for the dip stick tube to add fluid. I'll have to take a look, as I don't recall seeing that tube (sealed).

Pmarino

atchisvw

I’m troubleshooting a non-communication fault with my ECU and found a small amount of oil at the TCM module? Is it possible that it has wicked up from the transmission?

CamanoE55

If you read through the thread, I believe you will find that this is exactly what they are discussing being the possible reason for the OP's issue. His may have been clean, and it was another issue, but the fluid wicking up to the TCU is a well known cause for problems.