Overfilled transmission? - PeachParts Mercedes-Benz Forum

haromaster87 · #1 09-05-2012, 06:53 PM

Hey Guys,

I have a 1984 Mercedes 300D with an automatic transmission. When I received the car, the previous owner had the trans service at a reputable indy Benz mechanic not too long before I got the car. Based on the service, I know they would've had to put fluid back in the trans. Stupidly, I never thought to check the trans fluid because of this. This is my mistake.

I recently have been checking on different things. I know there is a great deal of trouble measuring the trans fluid in these cars as seen in the many threads I've read on it. Apparently you have to get the trans up to operating temp, then pull it through all of the gears, then let it sit and let the fluid settle, but there is a great deal of debate on how long that takes, etc.

I also read that a lot of people found that you can just measure the fluid level when everything is cold, and that it should come up about 10mm below the lowest level line.

I went out and checked mine, and much to my surprise/horror, the level is like 30mm above the max line. And that's with the trans cold. I don't know how they could've messed up that bad. I assume they filled it to capacity of trans and torque converter without draining the torque converter.

I'm going to get a new trans filter and put new fluid in at the correct level. My concern is I've been driving like this for a good while.

As of right now, it seems to be okay. It shifts well, shifts are a bit stiff and downshifts are clunky. I'm pretty sure that's more to do with my vacuum system though. First off, is it possible my cold fluid reading could be off? And on top of that, could my transmission be damaged from this?

Graham · #2 09-05-2012, 07:03 PM

Quote:

Originally Posted by haromaster87

As of right now, it seems to be okay. It shifts well, shifts are a bit stiff and downshifts are clunky. I'm pretty sure that's more to do with my vacuum system though. First off, is it possible my cold fluid reading could be off? And on top of that, could my transmission be damaged from this?

I once had something like that happen. Tranny shops just don't seem to know how to fill these transmissions.

I found out after a day or two, because transmission didn't seem normal. From what I have read, the fluid can get kind of aerated if overfilled.

I just sucked some fluid out until I got the level right and its been working fine since (several years).

If you are doing the cold level on a flat surface, it is hard for it to be wrong, except sometimes the dipstick is hard to read.

With what you are doing, I would think you should be fine. Just set level properly. Cold first, then check when hot and adjust if need be.

shertex · #3 09-05-2012, 07:27 PM

Just to confirm...your cold reading, that's with the engine running, correct?

jay_bob · #4 09-05-2012, 07:39 PM

Be careful, overfill can lead to an engine bay fire. The excess fluid backs up the dipstick tube and spews out, when it expands due to the normal operating heat. Well guess what's right under the dipstick, the exhaust manifold.

haromaster87 · #5 09-05-2012, 07:42 PM

Quote:

Originally Posted by shertex

Just to confirm...your cold reading, that's with the engine running, correct?

...Oh geez. Let me go try that now. Do I just need to turn the car on and check the fluid or do I need to turn it on, pull it through the gears and then check it? I feel like a dunce. haha

jay_bob · #6 09-05-2012, 07:57 PM

From the 123 Diesel owners manual, p.67 in the copy I found online (too lazy to run outside and grab mine) this looks to be a late 70s 200D/240D/300D version, but I would think it's the same for yours.

"Check transmission fluid level with the engine idling, parking brake engaged, and selector lever in position "P". The vehicle must be parked on level ground. Before the check, allow engine to idle for approx. 1 to 2 minutes.
Complete cleanliness must be observed! To wipe the dipstick, use a clean, lint-free cloth (or better still leather). To fill the transmission with fluid, only pour it through a fine-mesh filter into the dipstick opening. Even the slightest impurity may cause operational troubles.
The fluid level in the transmission changes with the temperature. The markings on the dipstick (max. and min.) refer to a fluid temperature of 80C/176F - normal temperature with the transmission warm.
At a fluid temperature of 20-30C/68-86F, however, the maximum fluid level is about 30mm/1.25 in below the dipstick minimum marking. This information serves as a guide for fluid change which is generally carried out at this temperature.
The fluid level should not exceed the upper mark and any surplus oil should be drained or siphoned off."

haromaster87 · #7 09-05-2012, 08:14 PM

Alright, I feel like a moron. It would appear my fluid level is right on. I can now trust that indy Benz shop again and write this one off to user error. Thanks guys!

shertex · #8 09-05-2012, 08:30 PM

Quote:

Originally Posted by haromaster87

...Oh geez. Let me go try that now. Do I just need to turn the car on and check the fluid or do I need to turn it on, pull it through the gears and then check it? I feel like a dunce. haha

Turn on, go through gears, then measure.

Glad it was just user error....we've all had more than our fair share of those!

I like measuring cold since it takes the guess work out of how hot the fluid is. I know some in these here parts are agin' it. But if it's good enough for the MB service manual, it's good enough for me.