722.6 Suddenly my Trans fluid level is very high
 

In preparing to go to FL the weekend, I was checking things out. I noticed my Trans fluid very high on the stick and starting to get a slightly brown tint. I have checked this fluid many times in the passed and while it is a bit tricky I have never been so surprised to see it so high and I don't recall adding fluid in the last 7 years. So I'm at a decision point do I go or do I stay.

The car in question is a 560SL using the power train from a 1996 SL600. See thread (M120 into 560SL). It is utilizing a complete power train from a 1996 SL600. Engine Trans Differential. My understanding is that the 96 722.6 transmission is very troublesome. The power train had 45,000 miles on it when I got it and I rebuilt the transmission to apply some updates. When I got into it I found the updates have already been applied meaning someone had trouble before 45,000 miles.

So the transmission now stands running well for the last 7 years but fluid turning slightly brown and unexpectedly high for some unknown reason. There is about 15,000 miles and 7 years on it since the last overhaul and maybe 30 to 50 blasts down the 1/4 mile.

Any MB techs with experience with this vintage trans.

John

Fluid level rising in the trans is a sign of the radiator leaking antifreeze into the transmission cooler. A glycol test will verify.

You may get by with a new radiator and a transmission flush, but don't bank on it. Worst case scenario... glycol can contaminate the frictions and water can rust and seize pistons and valves.

I'd swap the rad and flush it, then see how shifts. Monitoring adaptation if possible will provide insight on how much damage is done. Barring that the seat of the pants will let you know.

Glycol Test? How do you do that.

It would have to be a real small leak as I'm not loosing fluid. But we are talking about a qt high. Might be small enough not to trip the coolant low light. So worth checking thanks.

Google says

Glycol In Lubricating Oil - Detection, Analysis and Removal

If you have got coolant in the transmission it is a total bugger - the emulsions formed inside the unit are really difficult to get out and corrosion sets in pretty quickly.

what kind of dip stick are you useing? is this the same as you used before?
Is engine and trans temp the same as last time? Is it on level ground? all of that will matter. If you had a quart of antifreeze in trans oil ,it would look like a strawberry milkshake not dark it gets whiter.
correct fluid level and road test if all is good yes i would take it out of town.

check if fluid is pink.If trans is not sliping either get new radiator or use a external trans cooler.I found it was cheaper to go with trans cooler,its better anyways.The two ends for transmission on the radiator just block off.Change your fluid,and disconnet side going to cooler to pump all pink fluid out.

John,
You know more about these things than most of us here! But I can understand why you are puzzled by the high level.

As has been said, brown colour doesn't point toward water/glycol being in fluid. More likely overheating (from those 1/4 miles?? ) Maybe some frothing causing higher level? If coolant leakage suspected, I guess you could remove the trans cooler hoses and pressure test the cooler for leaks?

I have an E320 with the same 722.6 transmission. Originally they were sealed for life! But now there is a special dipstick. Home made ones will work, but it's not just a matter of pushing a wire down the diptube. The factory dipstick has a stop on so it doesn't go all the way to the bottom.

Temperature is also very important. I use a piece of plastic tubing as a dipstick and pass a thermocouple (DVM accessory) down the middle to measure the temperature. This diagram from this BW thread gives some idea of the affect of temperature. Level should be measured with ATF at 80C. I think difference between min and max when hot is only about 0.2L, so that would not explain your 1L (How did you determine that volume?)

http://www.benzworld.org/forums/atta...1&d=1383882105

forgot these tranny have carbon in the clutch packs,might not be pink.

ATF being brown is overheated ATF and if its the old 236.10 or 236.12 ATF it will discolor to a yellow/amber just like chrysler ATF+4 and Allison transynd ATF - they still are serviceable.

rising level is a bit strange - glycol mix would cause major problems and show up as milkshake like mentioned above - the worst part is that the clutch material delaminates when water/glycol hits it. The glycol also forms gel blobs when mixed with either engine oil or ATF.

We are believing you checked ATF when hot in any case (you mentioned you tore into the transmission). Quite oddball.

I've seen enough coolant enter the transmission for it to leak fluid from the overflow vent and not have a milkshake consistency. It was brownish. If you dumped a quart in all at once it probably would but a longer term slow leak wont.

You could always drop the pan and look. A trans fed antifreeze from the cooler will almost always have rust pock marks all over the pan and steel valve cover plates.

Any good MB shop will have glycol tests on hand. You could take them a small sample of fluid to test if in question.

Something that is easier to do than an actual glycol test of the ATF is to pressure test the radiator and see if looping or blocking the cooler lines makes a difference. This has worked well for me with old trucks at least.

Either way I'd think you'd want to change the fluid since there is no good reason for the level to rise.

Baring a coolant issue. The .6 will brown the fluid due to clutch material and not overheat. I've taken a few 165 K range units apart and have seen brown fluid with no signs the trans was failing.

Thanks for the replies guys the car made the trip to Ocola FL and back safely. Shifts smoothly and runs well. High fluid level has me at a loss not no increase in level after the trip. The discoloring of the fluid is by no means a concern at the moment but its more typical of what I see of cars with 150,000 miles.

I do have the MB dipstick and recently picked up a DVM with TC input so I will be using that. The 1 qt high was just a rough estimate based on how muched I drained out of the converter to get the fluid level right, but it was not measured.

That was my thought and that's what I did. Worked flawlessly. Most likely reason for fluid level error is probably fluid temperature not being measured. I dident have a TC DVM until recently. Fluid color is my biggest concern only due to the limited mileage on the car.