ATF loss after long time parking; where is front input seal?
 

According to Stu Ritter’s book, if the car is parked for a week or more, the ATF in the torque converter may drain back into the transmission housing. Then the ATF may run out of the front input seal.

I want to know whether my ATF ran out of the front input seal. Where is the front input seal?

I did not park my car over a week or more, but I parked my car for five days in the early January.

I checked the ATF level a few days ago. I had to put 400 ml to have the level between min and max. I did that after driving 50 minutes (not on highway, not in heavy traffic jam) so that the transmission is at normal operating temperature. The coolant gauge was between about 85 and 90 as usual. The ambient temperature was about 40 degrees F.

The last ATF level check was only three months ago; 400 ml loss in three months is quite a large loss.

1992 300D, 303 k miles. 722.418

P.S.
I did not have any puddle below the car. There is vinyl covered sponge on the black plastic noise shield panel below the transmission. The vinyl in my car is torn, and the sponge absorbs the ATF and releases the ATF slowly.

A/T vaccuam modulator leaking will suck in ATF and burn it . no leakage puddles yet a oil loss

Thanks. How can I check whether this is the case with my car? The vacuum line from the vacuum modulator on the transmission to the vacuum control valve right behind the injection pump is white. If I disconnect that vacuum line from the vacuum control valve and do not see any red color stain on it, can I conclude that my ATF is not going into the engine?

Change your underwear
 

Friend, remove the plastic underwear below the engine and transmission. Park the car over a fresh piece of cardboard large enough to cover the floor area under the engine and trans where it is parked. This test will help determine the severity and general location of the suspected trans leakage. The plastic underwear on the diesel is as absorbent as Benz-Depends and may hide the leak.

ATF leak
 

My 87 300E leaks ATF when parked for a few days. As suggested by dpkreuze I put a clean piece of card board under it and didn't use the car for a few days, when I moved the car I noticed the red puddle. I got under there and saw ATF dripping from the torque converter.

I took it to the indy and he said that it was the front seal and that the more I use the car the less it would leak and the longer it was not used the larger the ATF puddle.

I was given an estimate of $1k for labor only (10 Hour job) to remove the trans and replace the seals plus "O" rings while they were at it.

I haven't done anything yet, I just use the car and monitor the ATF consumption.

I am really considering doing this myself with the information from others here that have done it.

Good Luck with yours!!!

To check the vacuum modulator for a faulty diaphragm, you can do the following:

1) Disconnect the vacuum line from the intake manifold. Inspect for any ATF in the line.
2) Connect a vacuum tester hand pump to the line and pump it down. It should hold the vacuum. If it doesn't hold vacuum then either the line or the actuator has a leak and needs to be replaced.
3) With the vacuum line off, rub inside the vacuum elbow with a Q-tip. You are looking for signs of red dye present in ATF.
4) You can leave a small piece of cotton in the vacuum elbow for the purposes of seeing if ATF fluid is making it past the modulator diaphragm. Cigarette filter works good too.


Good luck!



-tp

Oh, to answer your question, the front input seal is (drum roll).... At the front of the transmission around the input shaft.


-tp

Thanks for helpful replies.

The input seal seems to be inside the transmission. If the ATF runs though the input seal, and eventually comes out of the transmission case, where on the outside of the transmission does the ATF come out from?

It comes out between the tourque converter and the transmission. Do you not know how this is set up? Crankshaft is connected to fly wheel, fly wheel connected to the torque converter, converter rides on a shaft coming out of the trans mission (input shaft) and the seal is in between the trans case and the converter. This is all inclosed with in the "bell housing" on auto trans is actullay part of the trans case.. There are a series of vents You will only be able to look through to see if the the fluid is coming down between the trans case and the converter.
To specifically answer your question, toward the front of the trans ,out the bottem of the vents.
But honestly, Its more than likly you would need an entire reseal of your trans. Trans leaks can be trick to find some times, I know . There is several places I have seen them leak.

The bottom of the bell-housing.

Old seals can shrink. When the fluid warms them up, they tend to swell again and seal well. Many stop-leak ATF additives are sold, which basically are solvents that swell the seals. Typically a last-resort and not recommended by transmission experts.

Your seal is likely shrinking as it dries out from non-use as the seal isn't immersed in fluid when the engine is off. Once the engine is running and circulating warm fluid, it tends to swell the seal again, and the residual fluid will keep the seal swollen and sealing for some time after use.

My spare transmissions are kept over-filled (to the top) to avoid this. I have a friend with transmission shops and really old cars, this is how he stores his cars in the winter (overfilled). He then drains the fluid back to normal levels before starting (knows how much extra is in there).

the most probable cause of your leak is the front pump seal.it still requires the removal of the trans.while you're there it's a great idea to replace the reverse clutches which are the main thing to wear out on 722.3 trannies.easy job once front pump removed for seal [large o ring with small section].

Sorry about the hijack,
 

but that would explain my 2 second delay into reverse.

yes it would.there is probably no clutch material left on the steel bases.i think that it's a testament to the engineering that it still works.show me another car maker where that would be the case.

If it does eventually engage properly without slipping, indicates to me that the problem is in the control pressures and not the amount of material on the bands.

Yes, that describes my issue along with a very small leak. Driving it every day has helped the leak.