SluisM

Hi, I have W204 C class Mercedes C300 4MATIC. Right where the transmission cooling line connects to the radiator, it is leaking tranny fluid. Does anybody know of any part numbers for the O-Rings that go in this connection? I'm looking to start with that as that seems to be the most probable cause. The lines themselves are free of rust, corrosion, etc... It's just the connection right to the radiator where it is seeping real slow.
I can post a pic if it helps anyone.

Would appreciate any input on this thanks.

Plutoe

There differences---post your VIN!

SluisM

@plutoe Thanks for the reply? Can you be more specific? Why do you need the VIN number? Differences in what specifically? the O-Rings?

Bochakrrik

lovemyc300

Hi I have the same problem but at the bottom line. What did you do to fix it?

SluisM

Mine did indeed end up being the O-ring inside that was the cause of the leak. It was a very slow seeping leak. Replaced it in Feb of 2018 and been good since. I was not able to find a Mercedes part number for it so What i did instead was call my local MB dealer to get the specs for the O-ring (width...diameter etc....) and I ended up buying them from a BMW dealership who was close by. I bought one to replace the top and bottom and it was only like $8. It is easy to disconnect the tranny line, and you will only lose a few ounces of tranny fluid at worst.

But the pain is getting the O-ring in there. It has its own little special grove it fits into and you need small pick tools screwdrivers...etc to line it up in there. Just time consuming and tedious, plus you're at a funny angle doing it. But it Beats paying a dealer to it.

I'll see if i can dig up the BMW part number of the O-ring i got.

SluisM

@lovemyc300:

I found the receipt for the O-rings I used to replace the bad ones. It is attached. Hope this helps.

MJ50

moved to W204 forum...

lovemyc300

Thank you. I'll order them. For the bottom line did you use a regular wrench at it is at a weird angle

SluisM

No you do not need any wrench or socket/tools to remove the tranny fluid line to the radiator. That hex nut that you see does not need to come off. I don't believe it will anyway since it might be part of the actual radiator.

This pic here is the same as what you posted. All you will need to do is slide that black plastic piece AWAY from the nut (its like a locking cap) and then the line will come straight out of the connection without much effort at all, just be ready to cap the end of the line with something to prevent fluid loss and dirt from getting in. The process is exactly the same for both top and bottom. You should be able to use your fingers to slide that black plastic piece but might need little plastic pry tool to pop it loose.

Red arrow is the black plastic piece. Green arrow the nut that you do not want to touch. The O-Ring lives inside a little groove inside that nut. You will be able to see it when you disconnect the line. I had to use a little mirror and a flashlight to inside since the view is difficult.

lovemyc300

Ok thank you, I've tried so many tools to open that nut but It was at hard to access area like in the picture I sent. I will try that later today. Really appreciate your help will let you know how it works out. Thanks again

lovemyc300

Thanks again for your help. The o ring fit but it was still leaking. So I removed the aluminum line and inspected it and it seems to have some small pin holes that was leaking. So I replaced the line and all is well. Thanks again for all your help

roverben