Changed tranny filter, now pan won't seal!

[mplafleur]

Ok, what's the trick? I usef the torque wrench and tightened each to no more than spec (6 ft-lbs I think) and I only got 10 miles down the road before it all leaked out.

I tightened the pan and put in synthetic oil. I started the car and backed it off the ramps with no sign of a leak. We packed up for Oshkosh and drove away abliss to the stream of oil I must have left down the highway. I pulled off the road and into a gas station. I bought some cheap fluid and pored it in. It leaked right out of the pan. Getting underneath tha car, it was definately coming out of the seal. It is a new gasket and I made sure all surfaces were clean and it looks like the gasket didn't slip.

I've heard that this is a tricky one but this is rediculous. played around underneath while at the gas station and at one point tightened up the far center bolt and the far corner started pouring fluid so I'm certain it's the seal.

Help! I've got to drive this car.

[leathermang]

Did you use any sealant on it ?

If you did , how long did you leave it before you put fluid back into it ?

My foolproof method takes time I assume you don't have out on the road... Can you get a new gasket ?
If so I would get some Aviation Gasket Cement...shake it up or stir it well.... appropriate since you are going to Oshkosh...
you will need alchohol to clean it off you or anything it gets on... very messy... but very good...

You have to have everything eating off it clean... then put a thin layer of the aviation gasket cemtent on EACH surface you are dealing with... and let it tack dry a few minutes... then install to the correct torque..If you can do it tonight and leave it as long as possible before adding the fluid that is good..... when you have it off, did you check to see if it was flat on the sealing surface ? This is not the method I would suggest if you were home and could take two days to put it back together... when you get home email me and I will tell you about that method...Greg

[mplafleur]

Well I'm back from Oshkosh so It's too late to get the sealant, but I can use others.

I can take a couple of days to get it correct. I'll put insurance back on the 2.6 and drive it w/o AC.

I've got the MB sealant around here somewhere. Will that work? I could go to the airport if I need.

[billrok]

Michael, I just changed the fluid on my car. When I removed the pan I cleaned both surfaces COMPLETELY. I even used soap and water to remove all traces of grease, oil, or solvent. I then used a metric tap to chase all the threads on the trans case. Some of them were bad. I then used a thin layer of Form-a-gasket, the soft setting stuff, on the pan, placed the gasket on the pan and put another thin layer on the gasket. Before installing the pan, you need to check the pan for flatness. Previous owner or tech may have over torqued the bolts and deformed the pan holes which will prevent your new gasket from sealing. Use a flat edge and hold it on the pan edges and look at how it sits. Ball peen any holes down til they are nice and flat. Set the entire pan on a flat surface and make sure its not warped. I do not yet have a metric torque wrench so I just used the ol' "feel" method. I went around every bolt several times and snugged them up a little each time til everything felt tight and the gasket felt seated. I also used my wire wheel to clean every bolt completely! I used a dab of the same Form a gasket on every bolt. This is just my technique. I know a lot of guys who use silicone sealant and some guys who use nothing on certain assemblies. It worked perfect for me.

[billrok]

Michael, The avaition sealant Greg mentioned is awesome. Permatex Form-a-Gasket is wonderful. The gasket and pan do not care if the sealant is from Mercedes or not. I would not even use the MB stuff on my trans pan or my oil pan for that matter.

[leathermang]

LOL, that is just the name of the sealant...
you can find it in autoparts stores...
Be sure when you are torqueing the bolts ,, in addition to the good stuff William just mentioned,, to go in a star pattern... you will surely warp it if you go around it in clock sequence,,, and from the sound of your test it sounds like that may be what happened...

[rickjordan]

If you are using an OEM filter kit, then you shouldn't need any sealant. As for the ATF gushing out, one how much ATF did you add and did you empty the torque converter. When I changed the ATF in my car, I made the mistake of trying to add the "fill quantity" without first starting the car, to allow it to work into the converter. Since I didn't do that first, the ATF I was adding forced it's way past the gasket. Once I started the engine and went through the gears, the leaking stopped and I was then able to add the rest of the ATF.

[mplafleur]

Didn't empty the torque converter. Added 5 quarts.

Had the wife and daughter 'slowly' add fluid while I was under the car. Almost immediately... it started pouring out.

[engatwork]

You should not have to use any sealant on the tranny pan gasket. I have even re-used this gasket on the 300D without any problems. I'm sitting here wondering of your pan sealing surface may be damaged/uneven. I would pull it and do a thorough inspection.

[MVK]

Did same job on my 300TD. No problem at all. Even old tranny seal looked as good as new one.I think its something else.
I dont know on your car but on mine, the rubber seal is held in place by rubber clips( which are part of the gasket itself).
Once held in place, put all screws in and hand tighten all of them a few threads, slowly tighten the bolts on the pan across from each other. staring with the corner ones. While I was doing this, I was holding the pan with other hand in place. The trick is you want to make sure that the tightening happens uniformly all across the pan surface and in small increments.
I did not need any sealent. I did not use torque wrench, but went underneath the car after few days and check the tightness of all bolts again.

My feeling is that you have an uneven or damaged pan surface of the gasket is torn. Give it a good look.

MVK

[Ken300D]

In my way of looking at the transmission pan seal, you don't need any kind of sealant to "help" the gasket. It is a very soft, deformable and thick seal that is rather lightly pressed into place (with low torque on the pan bolts).

The first time I did the '87 300D, I royally messed up the job because the seal slipped off the pan as I was putting the pan into place. This resulted in the back of the transmission pan having no seal in place and fluid just poured out. I learned my lesson that you really have to have a good view of what you're doing and verify that the seal is in place (visually) as you tighten the bolts.

The other thing that can happen easily is to tighten down the pan bolts so much that you split the seal, cutting through it with the pan. It is a SOFT rubber seal and doesn't need to be as tight as other cars.

Further, I learned my lesson long ago that whenever you change oil, coolant or transmission fluid you run the car for awhile sitting still and look under it for leakage. Then you take a few short trips and check again. Once I had a spin-on oil filter gasket stick to the block rather than come off with the filter. The new filter didn't seal right against the old gasket of course, and it leaked rapidly onto the driveway.

And if you value the car, you will perform all these checks before you hand it over to the wife, significant other, siblings, offspring, etc. Many a car has been ruined by forgetting to add oil back after changing, forgetting the new filter, forgetting to tighten the oil plug - - and sending the car on its way.



Ken300D

[mplafleur]

I will look at it when I get home tonight. My very first thought was that the gasket moved, rolled, or something and it is not sealing. I couldn't see that this was the problem, but there is very little room to look. It was just odd that it did not leak when I filled it, but only after I drove it for a few miles.

[MikeTangas]

What I found works for me is to sit in the warmth of the sun and gently milk the seal. This warms the seal and allows you to slip it over the pan. What happens when the seal is cold and somewhat shrunk, as soon as you let go of it, the seal begins to return to it's smaller, shrunken size, and it slips off the edge of the pan.

Once the seal is warmed, and you put it on the pan, you have a short time to crawl back under the car and set the pan in place. While holding the pan in place, a quick look around the edges to ensure the seal hasn't slipped is all it takes. The last thing I do is gently hold the pan in place until all pan bolts are in and snugged up. Haven't had one leak on me yet. Knock on wood.

[-fad]

To add:

I've cleaned and lightly sanded the mating metal surfaces just a bit (just enought to expose a shiny metal surface- very light duty paper), wiped down again, and also ensured visually that both surfaces lay as flat as possible to each other prior to putting the gasket sealer/ gasket

Upon install, there may be a little play to the right/left/north/south when mating the trans to the pan, again I ensure as close a match to the lips/mating trans as possible

fyi- the gasket sealer I observe merely holds the gasket from moving around too much as the gasket is usally plenty enough to seal

I've seen trans pans that were inadvertantly kicked or stepped upon/ lip bent when off the car, and it affected the proper trueness/ straightness of the pan's leading lip.

Upon thinking, perhaps the trans filter inside is preventing the pan from sealing up close enough to the trans...bad trans filter or improper for application?


...just a few thoughts, hope this helps
-fad

[MVK]

Make sure you fitted the filter inside correctly.

MVK