Coolant in Transmission Fluid? Help! - PeachParts Mercedes-Benz Forum

mopart2 · #1 10-23-2011, 07:47 PM

Hello all,

I have a 1985 300SD (200K) that I just purchased and decided to do some basic routine maintenance on the transmission, but while I was draining the transmission fluid, I noticed that it looked brown or even green. At closer inspection, my drain pan looked green!

My guess is that the radiator is leaking through the transmission cooler and contaminating the fluid. The car seems to shift fine before. It shifts through all the gears and I didn't notice any flaring between shifts. It is kinda sluggish from a stop like it isn't shifting all the way down into first at a start, but I do count 3 shifts sometimes and other times I will start with the selector in "2" and it will not shift until I push it into "3" as if it didn't start in first. Anyway, I am a little more worried about the coolant contamination at the moment.

Has anyone ever had this happen?

I put a leak tester on the reservoir tank and pumped it up to 10 psi where it slowly leaked out, I would say a 1 psi/min or slightly longer. Not sure if there is a specification on this or what you guys think.

I also tried to plug one side of the transmission cooler inlets and pressurize the other while someone was looking for bubbles in the overflow tank. No bubbles, but I am not confident I got a good enough seal to really test it.

The radiator looks fairly new to me, I am trying to contact the previous owner to see if he knows if it was replaced recently. Maybe it was replaced and the fluid was never flushed?

Currently, I changed the filter and gasket and refiled with fluid. The car still shifts good, but I am not sure what to do?

Does anyone have any input? Any help is greatly appreciated.

Attached is a picture of my drain pan removed from the car.

Thanks,

Keith

kerry · #2 10-23-2011, 07:54 PM

Keep an eye on your transmission fluid. Coolant in it will turn it into a milkshake. Could be the coolant was left over from a radiator failure that has been corrected.

Mad_Matt · #3 10-23-2011, 07:55 PM

Do you have trans fluid in your coolant as well? If not flush and monitor your trans.

If it were me I'd try and Remove the trans cooler lines form the Rad and pressure test the coolant system to about 15-20 lbs. If you see coolant leak then you need a new Radiator.

The system might only leak when hot so you may want to test hot.

mopart2 · #4 10-23-2011, 08:19 PM

Thanks for the help guys.

I did pressurize the coolant system up to about 10 or 12 lbs. Should it just remain constant or is there some type of leak specification?

The coolant looks green with no signs of transmission fluid in the coolant reservoir.

The only thing that worries me is that I did fill up the coolant reservoir yesterday after adjusting the valves (engine cold) and today it looks lower. I am going to mark the tank and keep an eye on that as well. I really hope the radiator has been replaced to save me some cash.

Either way, what sort of damage can this due to the transmission? Should I be expecting a transmission failure soon?

And what is the best way to flush the transmission? Should I pay someone to get it flushed completely?

Thanks again,

Keith

tangofox007 · #5 10-23-2011, 08:24 PM

Maybe you should mix a few ounces of transmission fluid with a few ounces of antifreeze and see if the mixture looks anything like what you saw in your transmission pan. What I see in the picture doesn't look like any antifreeze/transmission fluid mixture that I have encountered.

pawoSD · #6 10-23-2011, 08:24 PM

If thats what your trans pan looked like after you pulled it then its 95% likely the tranny is or will soon be toast. Water breaks down the materials in the clutch plates.

The cause would be the cooler in the radiator failing and allowing mixing.

shadetree77 · #7 10-23-2011, 08:45 PM

maybe it's so old that the ATF lost all the color; i was looking at a SD once and the ATF had lost all of it's red color...looked kinda yellowish though

mopart2 · #8 10-23-2011, 08:55 PM

I just tried a mixture of equal parts dex III and coolant and it looked more pink in color, plus a little milky after I mixed it up.

I really hope that I don't have to replace the transmission. I don't even want to know what that will cost.

Maybe it lost its color, but usually it turns brown right?

shadetree77 · #9 10-23-2011, 09:42 PM

i think it will only turn brown if it's got too hot; your fluid might just have that greenish tint to it when it's inside the pan; if you have some left over maybe pour some into a clear milk jug and see if it's more yellow in color. since it doesn't have that milkshake look to it i would think that it just lost it's color...now that would mean though that it's be a very long time since the trans was flushed...i would be very careful about adding new ATF to it since it might start swelling the seals inside the trans...it might be ok if you didn't drain the torque converter (should only take a little less than 4 quarts to fill the trans)...

tangofox007 · #10 10-23-2011, 10:36 PM

Quote:

Originally Posted by shadetree77

...i would be very careful about adding new ATF to it since it might start swelling the seals inside the trans...

Evidently, the engineers who designed the MB transmissions didn't understand swolen seal syndrome when they included drain plugs in the design!

bigblockchev · #11 10-23-2011, 10:42 PM

I agree with Tangofox it doesen't look like the usual milky pink junk I have seen come out of transmissions. Usually the trans fluid is the most colored component of the emulsion. Drain fluid into a clear jar & warm it up If it separates into two components it is likely coolant. If not then it might be something else. ( Duckhams motor oil is green , maybe other things as well ) An oil analysis would tell you for sure. Cheers Dan

mopart2 · #12 10-23-2011, 11:20 PM

I do remember that when I stuck my finger in the pan it did look like a reddish tint as it dripped off my finger. I guess jumping to conclusions, I assumed it was coolant mixed in because I have never seen transmission fluid like this before and it just looked so green.

I don't think I have any left over as it is in my waste fluid bin mixed with just about everything else. I could drive it for a couple of days and then drain it out some more and see what that looks like.

Thank you everyone for your responses and knowledge.

Keith

mopart2 · #13 10-23-2011, 11:23 PM

BTW it did only take about just under 4 quarts to fill the transmission and based on the previous owners statements the car did sit for about 5 years in his garage, if that adds anything to why the fluid would change color. (I would think not, but just providing all the details).

pawoSD · #14 10-24-2011, 01:30 AM

Does your car have green coolant in it? MB coolant is orangeish color.....and is what should be in there....

vstech · #15 10-24-2011, 07:17 AM

4 quarts? did you drain the torque converter? I thought the trans held 6 quarts...