Having trouble locating the source of the ATF leak... - PeachParts Mercedes-Benz Forum

MercFan · #1 09-02-2010, 04:53 PM

This on my 300SDL - I recently changed the fluid and filter. I've put in a new pan gasket and was very thorough in cleaning the mating surfaces of the pan before I re-installed it in the car. I've snugged the bolts down, refilled with fluid and left it for a few weeks while I was travelling. Coming back this week I see the all too familiar puddle of AFT on the passenger side - it looks like the low point is the drain plug but the right side of the pan (pass. side) is pretty wet.

I've just sprayed it with Simple Green and will hose it down later today so I can see it better. Diving under there I saw that the gap around the rubber seal had some fluid in it but not much fluid above the gasket - I'm thinking that it's the gasket that's leaking but again - it's a new one....

Any clues on how to better locate it would be welcome.

Thanks,
James

Junkman · #2 09-02-2010, 05:57 PM

My leak was from the drain plug. I'd top up the fluid, not be able to see anything leaking then find the fluid down & a puddle on the floor after the car sat for several days. It was dirty under there which didn't help finding the leak. A new copper washer for the plug fixed the leak. Put some cardboard under the pan & see where the first drops hit.

sixto · #3 09-02-2010, 07:06 PM

It could be that the pan mating surface isn't flat or the gasket is crooked. Drain the fluid in the pan, remove the pan, remove the gasket then check the mating pan edges against a flat surface. Do the same after fitting the gasket.

If that's not it, it might be dipstick tube, bowden cable or cooler return line where they attach to the transmission above the pan mating surface.

There's also a couple of 'big' piston thingies, the secondary pump and the kickdown solenoid on that side of the transmission.

Sixto
87 300D

Yak · #4 09-02-2010, 08:17 PM

I vote for the dipstick tube O-ring. Or maybe the banjo bolt washers.

The pan seal is finicky - too much pressure warps it, not enough lets it leak. Good luck isolating it.

bobodaclown · #5 09-03-2010, 12:42 AM

Did you snug the bolts to spec? Make sure you snug them evenly.

Hit Man X · #6 09-03-2010, 12:46 AM

You sure it is not the converter seal or that stator bushing up there?

At this point in time, it is probably a multitude of leaks.. not just a single one.

MercFan · #7 09-03-2010, 10:09 AM

Quote:

Originally Posted by bobodaclown

Did you snug the bolts to spec? Make sure you snug them evenly.

At this point I probably over-tightened them... had a hard time with such a low setting on my torque wrench so I went 'by feel' - if anything they are too tight by now.

bobodaclown · #8 09-03-2010, 10:19 AM

I'd wipe everything really well. Then try using some Spray Deodorant (power based). Here's the cut and paste:
To provide contrast color, we would use a "spray deodorant/antiperspirant" that had talcum powder in it's formula. We would spray the suspect parts, seals, gaskets, seams, etc. with enough of the powder to turn everything white. Then we would run the engine and watch the area. As soon as the oil leaks past its defective containment part, it will turn the powder brown. There is your leak. The powder washes off with detergent and water.
link to site:http://forums2.gardenweb.com/forums/load/tractor/msg0514503426631.html

hope it works for you.
Good luck

toomany MBZ · #9 09-03-2010, 10:28 AM

It's easy to over tighten, as mentioned, such a low torque value, but that's what the problem was on mine. It leaked when I bought it, then I did a fluid and filter thing with a new gasket, tightened to specs, not an easy thing, no more leak.

MercFan · #10 09-03-2010, 10:46 AM

Quote:

Originally Posted by bobodaclown

I'd wipe everything really well. Then try using some Spray Deodorant (power based). Here's the cut and paste:
To provide contrast color, we would use a "spray deodorant/antiperspirant" that had talcum powder in it's formula. We would spray the suspect parts, seals, gaskets, seams, etc. with enough of the powder to turn everything white. Then we would run the engine and watch the area. As soon as the oil leaks past its defective containment part, it will turn the powder brown. There is your leak.

Brilliant - that's what I need to do; I'm also gonna have to buy a little torque wrench and set the proper tension on the bolts so they are uniform.

THx all -

Junkman · #11 09-03-2010, 03:34 PM

Quote:

Originally Posted by MercFan

Brilliant - that's what I need to do; I'm also gonna have to buy a little torque wrench and set the proper tension on the bolts so they are uniform.THx all -

Simply snugging the bolts a long with a new gasket was sufficient. They are small bolts & I've seen people trying to be precise with a torq wrench strip them. If you want to buy a new tool, feel free.

MercFan · #12 04-29-2011, 04:44 PM

Well, I tried to locate the leak using the 'powder deodorant method' but I still can't see it - it's way up there in one of the 'big' piston thingies on the very end of the transmission (Passenger side)...

Was wondering - what does it take to LOWER the end of the transmission enough to expose that area and fix that bugger?! I'm guessing I would need to take out the shifter lever inside the cabin before I start disconnecting the drive shaft to lower the trans... any useful links to the process would be appreciated so I can size this up relative to my mediocre shade-mech skills... Anybody in the area that would be willing to look over my shoulder on this one would be welcome to some food and beer...

Thx,
James

86-300sdl · #13 04-29-2011, 05:42 PM

Located half way up the trans, passenger side, and towards the rear end?

If it looks like a "housing" (see photo) of sorts it's the secondary pump. Seal that leaked on mine was not the housing to trans body seal but the end cap rubber seal.

Attached photo is also the seal kit you may need.

Kinda of a pain to get to and you'll need a jack under the trans pan to hold the trans up, drop the cross member, and the rear trans mount too. Then lower the trans rear (tilt) low enough to get at all three bolts.

If it is this unit let us know because there are more "be careful" type tips you may want to know. Ya have to dissasemble it to change out the seals and it is a roast to get back together + re installing is another trick as well.

vtmbz · #14 04-29-2011, 05:59 PM

Remember this: theres lots of wind here. I thought I had a B-2 piston leak, but it turned out to be the dipstick o ring. It is very hard to tighten in place. Driving down the road blew the fluid from the dipstick to the back of the transmission in my case, and a .99 o ring solved the problem.

MercFan · #15 04-29-2011, 11:41 PM

Quote:

Originally Posted by robcarsonjr

Kinda of a pain to get to and you'll need a jack under the trans pan to hold the trans up, drop the cross member, and the rear trans mount too. Then lower the trans rear (tilt) low enough to get at all three bolts.

Rear trans mount too... boy - that may be a deal killer for me as I was previously unable to undo that big bolt from underneath. So does the gear shifter have to come out inside before I lower it (tilt it)?