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2008 Mercedes ML350 4MATIC
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Discussion Starter · #1 · (Edited)
I am getting mixed messages from mechanics in my area and I am a little desperate to figure this out so I don't end up spending a ton of money.
The car has 129k miles on it. I bought it from a guy for cheap a few months ago knowing the issues it had. It had power steering issues that turned out to be a seal which we fixed pretty quickly. The only other issue it had is that it also leaks transmission fluid.
I had one guy tell me leaks are extremely rare and that it could be one of these issues:
1. A pump which would be additional to repair.
2. It could be that someone filled the transmission fluid too much (which I could believe since the last person that serviced the transmission is bad at his job)
3. That it was my transmission having to be replaced..

The thing is since the car already had worn seals on other components why wouldn't the case be true for the transmission? Thats what another mechanic thought.

I have a few pictures of where the leak is coming from. I have the equipment and help to drop the transmission myself to look but I just want to know if anyone else has experience with this so I have an idea of what I am getting into.
2695788
2695789
 

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CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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Welcome to the forum @mountaindrew - please take a moment to read the information on the link below. It explains how to update your user profile so that your car's details and your location appear on each post below your avatar. This is good information for others to know when trying to help. It also has good information about how the forums are organized and how to use the search feature:

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I moved your thread here from the "Diagnsotic Tools" forum since your question is specific to this chassis and not general discussion about tools.
 

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2008 Mercedes ML350 4MATIC
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4 Posts
Discussion Starter · #3 ·
Welcome to the forum @mountaindrew - please take a moment to read the information on the link below. It explains how to update your user profile so that your car's details and your location appear on each post below your avatar. This is good information for others to know when trying to help. It also has good information about how the forums are organized and how to use the search feature:

Find your Forum Section, Navigate & Search

I moved your thread here from the "Diagnsotic Tools" forum since your question is specific to this chassis and not general discussion about tools.
I appreciate it! Just changed my info and edited the original post.
 

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CURRENT: 2011 SL550 FORMER: C300, ML350, CLK550 Cabriolet, C240, ML320, 300TD
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That's definitely transmission fluid and it's not form an overfill. There is a one-way vent on top of the transmission that will expel fluid if overfilled. It will run out over the pan, not the bell housing. I suspect you have a leak from the front transmission seal, which is on the fluid pump. While it is possible to drop the transmission and just replace the seal, my advice is to replace the entire pump. The reason is that your pump likely uses a sleeve bearing that will wear, allowing the torque converter output shaft to damage the seal. The revised pump uses a needle (roller) bearing that will last much longer. Replacing the pump means disassembling the gearsets inside the transmission. It's not an easy job, but it's just wrenching. While doing this, you might consider installing a transmission rebuild kit with new bearings and clutches.
 

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I had the same leak and I fixed it with a bottle of "Seal Fixx" made by Lube Guard and sold at O'Rileys auto parts. Not only did it seal the front seal tranny leak, but greatly improved the shifting.

Don't get talked into an expensive rebuild.
 

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I had the same leak and I fixed it with a bottle of "Seal Fixx" made by Lube Guard and sold at O'Rileys auto parts. Not only did it seal the front seal tranny leak, but greatly improved the shifting.

Don't get talked into an expensive rebuild.
Thanks for this info.
 

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2008 Mercedes ML350 4MATIC
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Discussion Starter · #7 ·
I had the same leak and I fixed it with a bottle of "Seal Fixx" made by Lube Guard and sold at O'Rileys auto parts. Not only did it seal the front seal tranny leak, but greatly improved the shifting.

Don't get talked into an expensive rebuild.
I'll give that a shot. Could that be a long term fix though? Did you apply it the same way you fill the tranny with oil?
 

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Discussion Starter · #8 ·
That's definitely transmission fluid and it's not form an overfill. There is a one-way vent on top of the transmission that will expel fluid if overfilled. It will run out over the pan, not the bell housing. I suspect you have a leak from the front transmission seal, which is on the fluid pump. While it is possible to drop the transmission and just replace the seal, my advice is to replace the entire pump. The reason is that your pump likely uses a sleeve bearing that will wear, allowing the torque converter output shaft to damage the seal. The revised pump uses a needle (roller) bearing that will last much longer. Replacing the pump means disassembling the gearsets inside the transmission. It's not an easy job, but it's just wrenching. While doing this, you might consider installing a transmission rebuild kit with new bearings and clutches.
If this is the case would I be ok with going for a used pump online? Or if I have to go to lengths get another preowned transmission all together?
 

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Assuming the problem is that the fluid pump bearing is shot and allows the torque converter shaft to wobble and has cause the seal to wear, then I'd replace the pump with a new one with needle bearings. It will last "forever" and will also be much quieter than a worn sleeve bearing (do you notice whining coming from the bell housing at idle?) The challenge in that is you have to pretty much disassemble the entire transmission to get to the pump. It bolts on from the inside, so you can just pull the bell housing off and install a new one. I'd not go to all that trouble to install a used part. I would definitely not swap out the whole transmission with a used one - you might get one with the very same problem you have.

I think if I were you, and did not want to invest a lot of money or time on this, I'd just replace the seal to keep the driveway clean. This can be done without any opening the transmission case. Once you separate the transmission from the engine, you can (gently) pull the seal ring out and press a new one in place from the outside. But again, if the root problem is a worn bearing, that seal will eventually get worn and leak.

If you do decide to drop the transmission, I'll give you one big caveat: Make darned sure that the torque converter shaft is properly seated in the fluid pump. The pump has two keys that must align with the two notches on the torque converter shaft. If they are not aligned, the torque converter will stick out about 1/4 inch too far. When you go to mate the two halves of the bell housing, they must fit together completely flush. If there is a small gap, it means the torque converter is not properly seated. If you "pull-in" the bell housing halves with the bolts, you stand a good chance of damaging the flex plate (a.k.a. flywheel) and possibly the torque convertor and fluid pump. It is challenging to get the converter properly seated AND to keep it in place while moving the transmission back in place. I have found that using something like zip ties to hold the torque converter to the bell housing work. You can then cut them and slide them out once you have the bell housing halves mated but not bolted.
 
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