mysterious dissappearing ATF????
 

Hello Forum Friends,

I have a new to me 82 300 CDT and am having a confounding problem. When I 1rst got the car the trasmission was shifting fine...no prblems. I had a worn trassmission mount replaced in Chattanooga TN where I bought it and then drove it home to Kentucky, no problems.

After having it home the transmission started shifting rougher and rougher on periodic errands out. I checked the ATF fluid and found that the level was scary low.

I added a quart of fluid and took her out for a spin. Shifted perfect. I waited a few hours and checked the level again (it was hard to get a reading right after filling the fluid went in the tube since it was coating the sides) the fluid was still low. I put in another quart.

The next day or 2 car started shifting rough again, I checked the fluid and it was super LOW again....Long story short I have now added 4 quarts of fluid and after the shortest drive the fluid level is close to empty again. There is NO ATF fluid leaking out the bottom. None! Where is the fluid going? Is it possible that their is some vacuum hose hooked up wrong somewhere that is sucking out the fluid???

I am mystified. Any ideas out there?

Have you inspected the transmission cooling lines and hoses for leaks?

trans needs to be FULL OPERATING TEMP. Slight inclines in any direction mess with the readings. Find a level spot where you can repeatedly check your levels.

check levels in 'P' and 'N' and shift through all the gears beforehand

The fluid May be going through the modulator valve, into the vacuum system and ending up in the engine....:D

According to the type of vac. pump, it may end up in the engine-sump or it may end up being burned in the engine via the vac-pump vent pipe to the air-filter....:eek:

I haven't noticed any leaks anywhrere. I think after adding 4 qts of ATF and the fluid close to empty again it should have been hard to miss, shouldn't it? Thanks

Wowee, this could be it! Where is the modulator valve? How do I check? Could it be sucking out this much fluid?

Just a thought, it might be leaking out only when the car is running, not when shut off. I had a similar, though much less severe, issue with this back some time ago. The leak never got bad enough to pursue/track down (this was 8/9 months ago) and I check my fluid often now. I still get unpredictable readings even at full temp and on level ground. The dipstick just doesn't seem to give readable readings--one side of the thing is full halfway up, the other side dry, etc. etc. As long as there's fluid on it within the marks at some point on the dipstick I just go with it....

But yeah, look into the "leak only while driving" issue. Should drive you fairly close to insane trying to determine the source.

JBG

there could be a possibility that the atf is leaking into the radiator?

Is the coolant reservoir overflowing and or have oil in it?

Charlie

Pull the vac modulator hose off the modulator. If it is leaking past the modulator the hose should be wet inside with ATF, mabe even full judging from the amount you are losing.
Look at the coolant to see if there is oil in it. You may have to disconnect a hose to check it if your car has a coolant recovery tank. If it has oil in it the coolant should be milky looking, maybe with beads of red mixed in not clear green like antifreeze.

The vacuum modulator valve is located on the Driver's side of the transmission case (assuming LHD American car) and connected to a valve on the Injection-pump, by a thin plastic semi-rigid pipe. From here, it goes to the cam-box where it connects to a vacuum 'micro-switch' then into a the main vac lines....

You can check for ATF fluid at any point along these pipes.. There should be no oil at all in those pipes....:rolleyes:


Worth checking the radiator isnt full of ATF though as others have said, If it is then the trans cooler pipe in the bottom of the rad will have rotted. This could also allow water back into the transmission and this could seriously damage it!:eek:

i just fixed a mudulator that was leaking trans fluid in.

I'd check your coolant level.. Charlie has a good point because the trans fluid is usually cooled in the bottom of the radiator and I've head of some cases where the trans fluid will leak into the coolant or even coolant into your tranny :eek: Also, if this is a vacuum problem you should be able to take apart your air cleaner and see that it is soaked in fluid. Do you notice excessive smoke in your exhaust? That's a sign of burning ATF.

Check your engine oil level also.
It seems hard to believe that that much ATF can be drawn up thru the small vacuum lines and getting burned but in theory it seems the best explanation for the ATF to escape without leaving a trace. If it's going into your coolant, unless your coolant was really low, you'd be overflowing with 4 extra quarts.

I checked all your ideas and heres what I found...
 

Hi Everyone thanks for your ideas,

Here's what I found. There is no ATF in the coolant, but the engine oil level is probably about 4 quarts high :eek:. I found ATF in one of the vacuum lines...I am posting a photos of this below...same line in both pics. There was a lot of fluid in the bottom of the air filter housing, but I couldn't tell if it was ATF or not.

So help the newbie...what does this mean? Does this confirm the faulty trasmission modulator or not? What kind of fix am I looking at?

Thanks again.

it looks like the tranny modulator is leaking fluid into the vacuum system. Then being dumped into the crankcase if that possible(someone back me up on that).

You must have a ruptured diaphragm in the modulator. Vacuum should be confined to the modulator itself. There is no other vacuum connection at the transmission.

A new modulator vavle should solve the problem. Buy a new pin while you are at it. Chances are good that the old one will break, if you have the plastic version. Then change the engine "fluid" and filter.

http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2G51AXQU82GY184T6Z&yearid=1982@@1982&makeid =MB@@MB@@X&modelid=300%2DDT%2D001@@300D++Turbo&catid=J@@Transmission&subcatid=J5020@@AT+Modulator+Va lve&mode=PA&subcatid=J5020@@AT%20Modulator%20Valve&applicationid=000010721&source=www.peachparts.com &clientid=catalog.mercedesshop

97 Mercy, you are correct, the vacuum pump "dumps" all the air sucked out of the vacuum system right into the air cleaner.

That explains the fluid in your air cleaner, that is the only way any fluid is going to get in there besides it sucking in water (rain, carwash) or the EGR (which makes more of a soot black paste crap)

How on earth would the vacuum system vent the ATF into the crankcase guys? It should burn instead of being pushed into the crankcase by the positive crankcase ventilation system, shouldn't it?

Which vacuum line are you talking about? If you pull the line right off the modulator (passenger side of most trannys) and it has fluid in it then you know it's the modulator.

Not on a 1982 300CD. That model should have a reciprocating vacuum pump which vents into the crankcase.

On a 1982 300CD, the modulator valve is on the driver's side.

I was thinking about a 240D, sorry about that tangofox007 is correct.

Exact same thing happened to me about a 2 months ago and a new tranny modulator fixed the problem.

On a side note, I did an oil change after that so I can get rid of the "tranny-fluid-contaminated-motor-oil" that I have in my engine, and guess what.....Mobil1 synthetic transmission fluid flushed the soot in my engine. Believe it or not, the new oil that I put didn't turned black until the 2nd week since the oil change, usually the oil turns black right after the first start up right after the oil change while checking for leaks......

Thanks
 

Thanks everyone for helping me diagnose the problem. I am going to order the part online and then have an indy do the work for me on this one. I will post again after the work is done and let you all know how it went.

So is this the pin I should order? http://catalog.peachparts.com/item.wws?sku=J5019-74125&itempk=68961&mfr=&weight=0.01&cookieID=2G51D862K2GZ1A3ZRL&source=www.peachparts.com&clientid=c atalog.mercedesshop

And if so do I use it with the modulator you posted above or with this one?
http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2G51D862K2GZ19ZJXO&yearid=1982@@1982&makeid =MB@@MB@@X&modelid=300%2DCDT%2D001@@300CD++Turbo&catid=J@@Transmission&subcatid=J5020@@AT+Modulator+ Valve&mode=PA&subcatid=J5020@@AT%20Modulator%20Valve&applicationid=000010734&source=www.peachparts.c om&clientid=catalog.mercedesshop

Thanks again

Been there, done that. My 82CD did the same thing earlier this year.

Read up on setting up the trans, before doing this yourself.

My '82 300D has the 722.315 transmission and uses the green mod valve and the pin as listed above. Just to confirm, you might want to check the transmission listed on the vehicle data card (block 7) or take a look at the actual mod valve to see what color you have.

where do I find the tranny #
 

Where do I find the tranny #? I looked in the maintanance book and the vehicle data card is not attached. Where can I find it on the car?

Thanks

If your transmission is original, you should have the 722.315. According to some sources, the 722.416 was used in the '85 Califiornia W123 models.

The easiest thing for you to do is probably look at the current modulator. If it's green, order a green one.

Repair Finished...But a new question
 

Hello everyone,

I bought the modulator and pin online and just had the work done at Erol's Autobahn in Nashville TN. $40 in parts and $105 in labor...not bad at all!

Mechanic told me about a separate problem that I would like to run past fellow forum members... He said that their is a separate vacuum line that is sucking break fluid out that is connected to the transmission?!?

He said that I had a small leak at the front and rear tranny seals and that if I wanted he could drop the tranny and change the seals and fix this vacuum line at the same time.

Any idea what line he is talking about? Any way to fix without dropping the tranny? Seems like if I am going to have the tranny seals replaced I might as well have it rebuilt while its dropped out...what do you guys think?

In order for that to happen, the brake master cylinder would have to be leaking brake fluid into the brake booster. The transmission would not be directly involved.

Have you observed any transmission fluid leaks? That sounds like it could be part of the mechanic compensation enhancement program.

hmmm...maybe
 

That is possible. I had not noticed, but he said it was a small leak, so I am going to put some card board under it to see anything is leaking.

As for that break line....I could not really understand what he was talking about. He said that there was a break fluid being sucked into the crankcase and that the line was connected to the transmission...I am not sure... does that like anything based in reality?:confused:

For starters, the entire vacuum system is interconnected. The only possible contact with brake fluid would be associated most directly with the main vacuum line that runs from the vacuum pump to the brake booster. Even then, in order for brake fluid to enter that line, the master cylinder would have to be leaking from the rear shaft seal into the brake booster. Which is possible. Are you loosing brake fluid? If not, I would be a little suspect. If you are so inclined, take the master cylinder loose from the booster and see if there is any fluid present.