transmission oil leak after car sits

[jhpcat]

This problem has been going on for years, and I am finally reaching out to you pros to get some guidance as to why this happens.  I previously stated (different post I just removed) that I thought it was coming out of the speedo cable.  After about 6-8 weeks of the car sitting, I crawled under the car last night to get a closer look at the leak. As it turns out, it may NOT be coming from the speedo cable.  So, if anyone has ever had this happen to them, please suggest as to what might be causing this problem.  The leaking begins about a week after it sits and I am constantly having to top it off. It's now a basketball size puddle.  The car has been completely restored and last year placed at the Hilton Head Concours d'Elegance. Just grateful they didn't ask me about "any transmission leaks". Images attached from last night.

[Nicolas Aristodemou]

It could be either the gearbox sump gasket - which means replacing it and tightening all the sump screws all around uniformly - or the oil seal at the output side -prop side- of the gearbox. Hopefully the sump gasket/screws. Only way to find out is to clean the area well with brake cleaner and wipe it clean afterwards and then see where the leak is coming from. If it is coming from above the sump - then it would be the seal; if the casing above the sump gasket is clear then it would be the sump gasket which is easy to replace. You might have to also remove the thick steel stiffening plate (shown in your photos with the cadmium plated screws) to gain better access to the gearbox and propshaft and clean them.

[Tycoon]

I had a similar issue..... mine was determined to be a leaking Torque converter. I found a shop in Toronto, Canada, “Converter Man”, complete rebuild for $150 CDN. Perfect solution.....everyone else was $1,000+ US...PM me for details.

[jhpcat]

thanks tycoon.  are you saying that the torque converter only leaked after the car sat for a few weeks.  Mine starts to leak a couple of weeks after sitting.  Bone dry until then.

[Pawel66]

My issue with similar symptoms was also related to sump gasket. I replaced it using a sealant this time and going carefully around the sump edge to straighten it near the orifices for screws.

Mercedessource offers a good video on sump gasket replacement.

[jhpcat]

thanks Pawel66.  Are you saying that it only leaked after the car sat for a couple of weeks?  thats odd for a pan leak. I really dont think its the pan. I can clean it up, drive it and its bone dry.  Only after sitting does it begin to puke.

[wwheeler]

Mine did that and was the speedo housing seal. It is just an O-ring. After about 3 to 4 weeks, it would start dripping. Torque converter would drain oil slowly and fill up the trans. Once it got to the level of the speedo housing, it would drip. Changed the seal and problem is gone. It looked like the pan gasket, but was leaking from above.

[Pawel66]

thanks Pawel66.  Are you saying that it only leaked after the car sat for a couple of weeks?  thats odd for a pan leak. I really dont think its the pan. I can clean it up, drive it and its bone dry.  Only after sitting does it begin to puke.

Difficult to say, but I did not see the leak in the autumn when I placed the car on the jack, then they were there in February.

[stickandrudderman]

My issue with similar symptoms was also related to sump gasket. I replaced it using a sealant this time and going carefully around the sump edge to straighten it near the orifices for screws.

Mercedessource offers a good video on sump gasket replacement.

Never use sealant on an auto transmission!

[Pawel66]

Too late...

I remember a discussion on this - some people used sealant, some did not.

Why should I not use it?

[JPMOSE]

I have never had to use any sealant for the 16 bolt pan gasket.  It sounds like you have a smashing 280SL fellow Atlantan...but do you think there’s a chance the oil pan is warped? I use MB or Mann parts for the  transmission filter/gasket and have always had a tight seal.

[jhpcat]

I just dropped my buggy off at Bud's Benz.  Brad Peterson is top notch.  Last night, I made one last ditch effort to get pictures while the car was sitting for so long.  And dont ya kno... I found a bright red ball of fluid hanging in thin air seconds before dropping to its resting place in my bed pan (oil pan on the ground).  That little beauty was right at the speedo cable as it enters the tranny housing.  Only conclusion is that this is clearly one leak.  Do I have others? (Parish the thought.)  Repair will be done before my chops even get into one of the Butterball drumsticks coming in a few days.  Stay tuned.  I'm just dying to be MORE thankful than I already am.

[wwheeler]

As I posted earlier, your symptoms were exactly like mine. The speedo reseal did the trick and hasn’t leaked in years. From my recollection, it is just an O-ring. But, need to inspect the speedo housing as well because sometimes they will crack from the clamp being overtightened. If yours is cracked, the housings were available back then.

Might also make sure you are using a Viton O-ring. Auto trans fluid is tougher on regular Buna - Nitrile O-rings than motor oil. Add in the heat from the trans, and viton is a much better choice.

Good luck.

[JPMOSE]

LOL....I just got back from Bud’s Benz… I had a small part I need and they happened
to have it in stock. Probably just missed you!

[JPMOSE]

This is a spoken message so there may be some grammar errors! I have another thought… Likely is leaking through the speedometer cable. The early transmissions a K4A025 And K4B050 had a check valve in the valve body Which prevents the fluid coupler from draining back into the main body of the transmission. With age, this will disintegrate and after the car sits a while the fluid drains back in and comes out the speedometer cable connection. From what I understand, the earlier transmissions did not have a seal or at least a seal used in later transmissions such as the K4C025 and K4A040. My friends Mercedes 600 will leak after sitting for a couple weeks and it comes out of the speedometer cable connection. When the check valve works correctly, this is never an issue. But I guess as the cars aged in the mid 60s… And the check valves would start to go bad… They realize that they had the beef up the seal for the speedometer cable connection.

[jhpcat]

SOLVED:  Brad (at Bud's Benz here outside of Atlanta), tore into it and found the jacket on the speedo cable to be torn.  Hence, the fluid that would begin to flow into the cable just flowed right out the hole.  I found that odd, because I remember changing out the cable with a new one. Shamefully...  I must admit that once I pulled the service records (my 4 1/4" think 3-ring binder), I did indeed find the invoice from 2002.  Worse yet, it was not even genuine MB.  It was from K&K Mfg, at 23 clams.  The new MB part is almost 300 clams.  Oh well; gotta have it.  The MB cables come with the fat rubber piece at the end of the cable, the K&K does not (back in 02 anyway). I am indeed thankful and can now I can forget about putting a sump pump in the floor of my garage just to pump out the leaking fluid (just kidding).  Brad will still replace the o-ring as he was "already in there".  Bottom line:  new cable and o-ring. problem found and likely solved.  Thanks for all the help fellas.  Moral support is good to have these days.