Need some help - PeachParts Mercedes-Benz Forum

psaboic · #1 09-20-2020, 09:01 PM

Hi folks.

Car in question is my wife's 2012 ML350, so I will also post in the ML350 section. Yesterday I changed the oil, air filters, fuel filter, and transmission filter and fluid. Today she drove it about 15 miles and it started shaking and losing power. We had it towed home and I had a little time to mess with it before dark.

No obvious leaks anywhere, so I took it for a drive. I got about a block and it did what she said it did. I stomped on it and it picked up very slowly and would not shift until I lifted up on the pedal. The engine is not revving like the trans is slipping, there is just no power, but it idles smooth and starts up normally.

The only anomally I had was yesterday when I drained the trans fluid out of it I got about 4.5 quarts out of it as measured by a measuring cup. So I refilled it with 5 liters of the proper blue transmission fluid. Now the transmission kit I got from ID parts came with two 5 liter jugs of fluid, but I only used one. 4.5 quarts = 4.25 liters

My questions....

First off, do you think I have a fuel problem or a transmission issue? Second what is the approximate amount of fluid needed for a drain and fill on a 722.9 transmission? Third, I drained 4.25 liters out and refilled with 5 liters. Is it possible the transmission still under filled, or overfilled (I don't see how .75 liters would cause this issue). Lastly, it first started after 15 miles of highway driving so the trans fluid was hot. Now it will do it after sitting for 6 hours and the fluid is cold.

psaboic · #2 09-20-2020, 11:20 PM

An update.* I started the vehicle and got a mild smell of diesel fuel from the engine bay.* Then, while it was in park, I ran it up to 3000 RPM.* It held steady at 3000 RPM for about 5 seconds then slowly started dropping in RPM even though the accelerator pedal was not released. Finally it dropped to about 1200 RPM, I released the accelerator and it shook and sputtered like it was going to stall, then smoothed out.* I revved it again*and it did the same thing.* I'm suspecting a fuel starvation issue now.* There are no check engine lights and it starts and idles fine, but if you rev it up, it will hold for a few seconds then slowly drop RPM's until it almost dies.* Wonder if my fuel filter I put in (a Mann with the 5 pin connector on it) is bad. or I have a bad fuel line.* Funny thing, I put cardboard under it and nothing seems to be leaking.

dieselbenz1 · #3 09-21-2020, 07:00 AM

If you had a Foxwell scanner you could watch the live data and test things like fuel rail pressure, charge air pressures etc. The adaptations for air filters could be reset also. I think I would look at air or fuel first but you would think a engine check lamp would also show. I thought the transmissions can not be over filled since they are filled from the bottom?

psaboic · #4 09-21-2020, 09:42 AM

Not familiar with air filter adaptation.....please don't tell me you have to reset a computer or something everytime a filter is changed...... If so, what model Foxwell scanner do I need to look at? There are many. Is there a DIY on how to do the adaption? Thanks for any and all help!

barry12345 · #5 09-21-2020, 10:40 AM

Transmission not the problem I suspect. Read using the spill tube to set the transmission fluid level. It sounds like you might have too much fluid in it. Not certain of the sensitivity of these transmissions to level of fluid. It is slow but you can fill these transmissions from the filter hole on top of the transmissions. Make certain it is right as these transmissions cost a lot of money. I suspect without knowing it the computer may monitor them.

I have no ideal of the source of your problem. I put 5 liters in the wives Passat transmission as recommended and it spilled out almost a liter. Then I too measured what came out versus what I knew what was left in. . It was close. Drain hole is at one end of lower case . Car must be level to use the spill tube properly. In both directions. The car was level fore and aft but may have been a little off side to side. I used front sub frame to establish side to side level. You do need a level to do these cars. Originally these transmissions where perhaps meant to never replace the transmission fluid. Every forty thousand miles recommended by volkswagon.

dieselbenz1 · #6 09-21-2020, 12:03 PM

I have the Foxwell NT520 but I think it has been superceded. Mercedes WIS calls for resetting adaptation used for air filters. I can't really see that being your issue though but this tool will let you see what's going on in your vehicle. I recently was able to check all fuel pressures and have a self test of the fuel system. I changed the fuel adaptation and the check engine light no longer is on. That was on a 08 GL CDI.

psaboic · #7 09-22-2020, 12:08 AM

All,

Many thanks for the help and all the suggestions, I'm pretty sure I have a fuel leak/issue. Tonight after work I had about an hour of daylight to mess with it, and long story short, the the engine plastic skid plate and the transmission skid plate as well as the cross member behind the engine are damp with diesel fuel. I noticed both were damp/stained and when I wiped the residual off it smelled strongly of raw diesel fuel. Sooo, I have a nice little fuel leak somewhere.

I'm hoping it is the fuel filter or one of the rubber lines, as that is the only part of the fuel system I messed with (fuel filter change). I guess the best course of action is either pull the skid plates and see if I can trace the leak that way, or pull the fuel filter and check the rubber line.

psaboic · #8 10-02-2020, 09:52 AM

Just an update. Ended up having to take the car to a shop as I could not find the leak. I was paranoid the high pressure fuel pump let go......turns out one of the fuel return lines buried under all the other stuff behind the engine had let go. $7 part, $135 in labor to get to it!