3 or  4 months ago, I changed the AT filter and pan gasket on a 2002 Lexus RX 300.  It worked fine until last week, when it started leaking fluid at the rear of the pan.  It was my fault. I failed to clean all of the old gasket sealant off the pan and overtorqued the pan bolts, causing the gasket to be crushed.

So last night I dropped the pan, cleaned it thoroughly with  brake cleaner.  I used 3m yellow gasket adhesive to adhere the gasket to the pan.  Gasket was OEM cork by the way.  Torqued the pan bolts to 69 in/lb per factory specs.  Waited 24 hrs to fil with fresh ATF.  No leak.  I drove the car into town, approximately 8 miles roundtrip.  When I got back home, I noticed a signifigant leak.  Put a pan under, crawled under the car, and observed that the gasket was pushed out at the rear edge of the pan. I am at wits end.

How do I get the leak stopped?  I have an aftermarket Fel-pro gasket which is rubber.  I also picked up some black hi temp gasket maker.  Should I use the gasket only, apply gasket maker to only the pan side, or apply it to both sides of the gasket? Thanks

Does the transmission have a vent that is plugged?

Not sure what you mean.

ETA: Just did a search.  Lexus aparantly did not put a vent hole in the tranny (Toyota did in the highlander, which is pretty much the same tranny, strangely enough)

I had a similar issue on my truck..  The problem is, when the ATF gets warm/hot it gets thinner and/or slicker, and it will leak from the tiniest places...

What I had to so was let the felt gasket get saturated (by running it for a few days).. Then i tightened up the bolts slightly and let it go for a few days and if it was still leaking it retighted again slightly until the leak stopped

Brian

Well, I'm keeping my fingers crossed.  I just applied a thin layer of gasket maker to the pan, just enough so that it would hold the gasket in place.  Handtightened all 18 bolts, then torqed to spec.  Hopefully, that fixes it.  If not, I give up and it is going to the Toyota dealership.

Answer is on page 117 of this magazine..
http://books.google.com/books?ei=iFRlT6KfA4WSiAKDl-2iDw&id=5OMDAAAAMBAJ&dq=use+a+ball+peen+hammer+on+a+oil+pan&ots=yqETcw8eDW&q=+peen+hammer+on+a+oil+pan#v=snippet&q=peen%20hammer%20on%20a%20oil%20pan&f=false

I like the sound of this stuff, but can you get the pan off for the next service or do you just trade the car off?
I've always had very good luck with just cork gaskets.



Sometimes I'll glue the gasket to the pan with Aviation gasket maker if it looks like I might bump it getting it into place.  Just a thin film on the pan, a few clothespins to hold the gasket in place, go inside for a beer break, go back out, install, fill and go.





My guess is the gasket came all wadded up in a small box didn't it, cripes I fvcking hate that.


If you can get the pan flipped over without the gasket moving and put something heavy on the pan, that works too.  Just double check your bolt holes before you leave it.
Be aware that anything you put on the gasket has the potential to go into the pan and through the filter while it's still in it's uncured state and collect in the valve body and stick a spool valve.  Not a big fan of silicone for this reason.  
Hope you get it sealed up.





 
 
 

Could be that the pan is wrapped.  I had a FWD GM car that had a trans pan that would always leak.  Someone told me that the pan might be wrapped or bent.  I finally picked up a used pan in good shape, bolted it up, and had no more leaks.

The black RTV (silicon goop) alone is the most positive way to stop a leaking transmission pan.  Chrysler has been using it on all vehicles since the 90's with excellent luck.  It has never leaked on me when I've had to use it.  It also is a good way to seal a pan if you have a couple stripped bolt holes that don't allow the bolt go be torqued down.  The problem is when it comes to take the pan off again.  I usually have to resort to beating the rim of the pan with a rubber mallet to get it to come loose.  It can also be a pain to clean off the pan if you don't have a power tool with a wire wheel brush.

So, my opinion is to tighten up the pan bolts a little more and see what happens.  If that doesn't work, try a new pan with a new gasket OR just use black RTV and never worry about it leaking again.  If you decide to use RTV, only use about a 3/8" (at most) bead around the pan.  It should just barely ooze out at the edge of the pan when torqued down.  Let it set up a little on the pan before bolting it up.  The RTV will attach to the pan and not the transmission if you do this.

RTV isn't really that bad if you don't use tons of it and have a rubber mallet and a powered wire wheel of some sort.

Is the pan cast aluminum or is it stamped steel?

Let the trans drip dry as long as you can.  Then clean the mating surfaces of the pan and trans with brakeclean.   Use Permatex "the Right Stuff" or Ultra Black.    

Lift the pan up in one step and bolt into place.   If you can't get the pan up without it sliding aroung and screwing up the Permatex, cut the head off a bolt that fits your transmission holes and install a few of those first to use as studs to guide your head on.

Make sure your breather is clear.   Fill your ATF in the morning after the Permatex has dryed.

Don't worry about Permatex inside the trans.  Filters?  How do they work?

The pan is pretty heavy, so my guess is that it is steel.

I did straighten the rear of the pan out with a piece of 2x4 and a hammer.  Hopefully, that will work.

Will the permatex stuff form a good seal even if the pan is warped a little?

Yes. That's the beauty of it.

Just be sure not to use too much of it because it will ooze out and could cause a problem. It's not really a concern if you have any sense though.

Not worth a shit when they're plugged full of cured silicon or one little speck of uncured gets sucked through the filter by the pump and sticks one of your spool valves.
Now, granted, you have to be a complete neanderthal to goop up a pan that badly, but it is possible and it's a bitch to diagnosis this kind of stupid.
But under normal conditions, with normal people. with normal skills, you are absolutely correct.



The filter will save you.
OP, if it keeps weeping and you end up taking the pan off again.  Take a little more time and make sure that pan is flat.  


Lay it on a flat surface to check it after each "adjustment".  


I'm thinking this is a large part of your problem.





What I'm kinda curious about is how the pan got dented.


There usually is a story behind it.
 
 

Please don't take offense, but if you can't tell cast aluminum from sheet steel just by looking at it, you probably shouldn't be dinking around with your transmission..  

It is definately not aluminum.  I said I'm guessing it is steel, because I'm not sure if Toyota uses some type of alloy or not.  Come to think of it does anyone actually use aluminum for a tranny pan.  Most pans have magnets inside them.

As to the problem, it is fixed.  The fel-pro rubber gasket and some permatex as a gasket dressing worked lilke a charm.

I didn't pay attention to the torque specs the first time I replaced the gasket.  I overtightened the pan bolts, which caused cupping along the bolt holes in the pan.

Dang, I was hoping for a:

"I backed over the kids bicycle in the driveway" or

"Grandma kinda forgot she was actually driving a car and went 4 wheeling." or

"I ran over a bowling ball on I-90."

kind of story.  Those are the first three that came to my mind.



Anyway, good job on the fix.
 

Cool, thanks for posting back.

I may have to join the modern era and try some.



 

This is why I was asking about whether it was stamped steel or not.  Even if you don't over torque the bolts, you need to peen out the bolt holes in the pan (flatten out the rail around the bolt holes - now that you've seen it you know what I'm talking about) every time you take it apart. Same goes for stamped steel valve covers, and most any other similar thingy.   A cast aluminum pan (yes, they are out there) won't have this issue, although they have other issues of their own...

OEM pan is a chemical sealant, not cork gasket.

Whenever we did a service on a transmission we used a small ball peen hammer on the holes of the pan to knock them out a little so they would seal when you installed it.