Hi All,

I have a pretty clean 82 240D auto with 172K miles on it. Drives very nicely and the trans is in good shape and has actually had regular fluid changes.

I recently switched to a synthetic ATF in hopes that it would clean up the cold weather shifting performance on chilly mornings. The good news is that is has.

The bad news is that there seems to be a VERY small leak from the front main seal. It's actually hard for me to tell because it does not leak when the motor is running but appears to leak over night. Leaves a spot about the diameter of a tennis ball.

I would hate to pull the trans out to fix a leak this small and don't mind topping off now and then but given that this is my wifes daily, I do want to air on the side of caution as I know she is not vigilant of leaks, and fluids get checked on when I check them bi weekly.

Has anyone had any luck with additives that perhaps swell the seals a bit?

Not looking for magic in a bottle here, just hoping I might slow this lil leak down.

You'll have to live with it unfortunately, I would not use any transmission additives at all.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Synthetics tend to find exit paths. Best bet is to go back to standard fluids.

Stop leak is basically brake fluid, this will swell all seals at an uncontrolled rate. Not only will the front seal swell, the clutch drum seals will too leading to stuck / dragging pistons and eventual transmission failure.

A leak related to engine off is generally pan / dip stick tube related because fluid level rises after sitting finding a leak point.

I've not had good success with ATF stop leak. Probably better off topping it as needed so as to avoid causing internal seal problems with a stop leak additive.

Is it definitely the front pump or seal.?Confirm it isn't the converter drain plug... here's hoping.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

When I used Lucas Trans sealer and conditioner it reminded me of STP but was pink. That made me think that it works mainly by making the transmission fluid thicker. (It did slow my trans leak down.)

But using the Lucas stuff would defeat the purpose of you switching from regular ATF to synthetic ATF.

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84 300D, 82 Volvo 244Gl Diesel

Fair enough, I'll stay away from stop leak products.
When I first noticed the leak I took a look @ the pan & drain plugs on it and the converter and didn't see anything.. guess I'll check again.

I did find it really strange that it wouldn't leak while running but would overnight if it were a seal on a rotating part.

Honestly, this trans shifts well... but if it's gotta come out for any reason a manual is going back in its place, Simply for the fact that the idle in drive @ stop lights is so much rougher than that of my stick shift 240D.

Did you try to raise / lower the idle speed a bit? Sometimes 50 RPM can make a difference.

Weird idea, has anyone every tried liquid gasket to fix small leaks like this? I certainly would not add any stop leak additives to anything. I've seen what it does to radiators, and it isn't all that pretty. In my opinion, it's better to live with the leak and fix it properly in the future.

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1981 Mercedes 240D - Automatic transmission

Radiator seal type additives work by getting stuck in the leak path. A sealer that uses this principle would not work with an auto trans as it would affect the valve body.

There is a radiator stop leak that isn't harmful, is stealth, actually works on seepy leaks. It is Bars Leaks Tablets, these are also sold under the GM / AC Delco name and probably other car makers. Consisting mostly of Ginger they won't clog a heater core that is in any decent condition. Crush the tablets into powder, install the cap and drive the car.

When my '81 240D's tranny reached about 250,000 miles it began to weep a pine or so a month, mostly when parked .

I asked here and a member who I don't see much anymore suggested "Trans-X" ~ I went to my F.L.A.P.S. and Lo ! many different varieties of this elixir, I chose the yellow plastic bottle and dosed it, the leak stopped and the tranny was good for several more years until the engine failed, I had it rebuilt at that time when it was out anyway .

FWIW, brake fluid in slushboxes is a very old used car lot trick and it's not wise as it tends to soften up that rock hard seal *so* much that one time when you shut it down on a hot day, the now soft seals lip sticks to the shaft and when you re start it ~ the seal fails completely .

I too am very hesitant to recommend any snake oil for slushbxes but Trans-X seems to work O.K. .

The torque converter's drain plug is on the edge and you have to slowly rotate the engine until you see it on the dead bottom, it takes a 5MM ATF Allen to remove it, not likely this is the leak .'

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better