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Transmission Secondary Pump Seal, Overflow Seal and Vent Tube Replacement
Based on the diagnostics by the dealership yesterday, and actually a prior inspection about 10 years ago (more of a seeping then), the source of the leak in my transmission is coming from above the transmission as the lower seals are well seated and dry. Unfortunately for a full inspection, it will require the transmission to be dropped from the car (which i am uncomfortable having it done locally).
Hence I have narrowed down the leak to 3 sources:
- Secondary Oil Pump in the transmission on the right rear (probably seal issue which is the same as other 722.3 in MB cars)
- Ventilation Line between the reservoir and the transmission
- Overflow Plug (on top of transmission) and its seal
Has anyone had issues with the above and replaced them or their seals with the transmission in the car? Feedback is appreciated so i can give instructions to the dealer on how to tackle it (hopefully tranny in place)!
Here is a pic of the vent line (left) and secondary pump (right)
whats leaking?
there is a drain hole on the interface plate of the diff and trans this so neither one will mix with the other unit
See that silver colored plate that mates the diff to the trans look for the hole
If the dealership doesn't know how to address these issues, you might not have the correct people working on your car....
The secondary pump can leak from two different places: 1. On the very "end" of the pump housing, there's a steel cover, which looks like a "soft plug. If the leak is from that cover, there is a thin O-ring on the OD of that cover, which can leak. Remove the snap ring to remove the cover, to replace the o-ring. 2. If the leak is around the actual pump, there is a large "O-ring: under the pump assembly, which can leak. The pump need to be removed to change that seal. Beware the shaft with the 10mm headed nut....it holds the governor in position, which can be dislodged.
The "formed" overflow hose from the transmission to the reservoir is/was NLA. I use a generic hose, which can make the bend without folding.
If the vent from the transmission is actually leaking....it should not ever leak. There is an O-ring seal on the vent body, but rarely is this an issue. 4 possible causes of oil ejection out of the breather. 1. The transmission is overfillled. Get the transmission hot and check the level. 2. Some transmission fluids are more prone to foaming than others. Change the the fluid. The Dextron from Pep Boys works extremely well. There are some high performance fluid, which foam less, also. 3. Excessive wear on the case/governor where the governor rides. Caused from dirt/debris/poor service. This is a disaster. 4. Leaking seal in the K2 clutch. At this point in time...all of the seals/o-rings in these transmissions are rock hard and seeping. The transmissions are way past their intended service life. The resulting slipping/wear on "hard parts" is catastrophic and makes rebuilding the transmissions many $$$$ more expensive.
Good luck. These things are an "art form" to repair, now that they are getting old. Knowing what parts to use, what parts to replace, what pieces got superceeded and what parts have multiple supercessions (change one part and 3 others must be changed) is knowledge that is long lost.)
whats leaking?
there is a drain hole on the interface plate of the diff and trans this so neither one will mix with the other unit
See that silver colored plate that mates the diff to the trans look for the hole
The weep hole is on the side of the transmission where the vent is....easy to mistake a leak from the weep hole for a leak from the breather,
The leak is all pure ATF... and it's apparently coming from above the transmission (above the reservoir area).
Greg,
For both the dealership in Lebanon (back about 8 years ago when it was more of a seeping) and in Saudi (yesterday) mentioned that the leak is not from the oil pan area but from above the reservoir and not directly visible to them and hence to properly figure it out, they need to drop the transmission from the body (which I am reluctant to allow... so i did my visual evaluation from photos of similar 722.3 ... I could only identify 3 point of rubber (seal on the top where you have the overflow plug, seal on the secondary pump (probable culprit) and the vent hose/reservoir). Hence I am wondering if those are serviceable while the transmission is in the car.
The breather shouldn't leak oil unless, a) transmission is overfilled, b)overheating (slippage) enough to raise "hot" fluid level above normal, if it were blocked however internal pressure (air) would find another route and it would leak from a dipstick, in this case, the cap on the reservoir.
BTW, go to a local NAPA, ask them for automatic transmission dye.
It's a fluorescent dye in maybe a 1 oz size, pour into the transmission oil (it's safe) and drive for a few days.
You could normally diagnose almost immediately on a conventional transmission because the dye goes right into the sump and is instantly picked up and distributed but the remote reservoir on your may hold the dye in there and delay distribution.
You will need a UV light (the dyes come as a "kit" if you chose to purchase that way) that you can buy separately.
In your garage, after you are confident the oil/dye has been circulated, close garage door and limit light sources (darker the better), shine V light around suspect area.
Leak will show as fluorescent green.
Just about impossible to mis-diagnose.
There are no leaks (visual) from the reservoir's cap, but I did not rule out a crack on the top of the reservoir's connection through the vent hose or the vent hose connecting to the transmission body. Still ii thought replacing those plastic parts are not expensive so no issue replacing them. On the other hand I was concerned about the secondary pump seal (which I believe might be the problem). Has anyone serviced those items on the car?
As a quick note, the dealership cleaned up the the car the day before to inspect in the morning. Upon inspection the next day there was ATF coming out from the top (so I guess it's not the breather on the top). This leaves 2:
- Secondary Oil Pump in the transmission on the right rear
- Ventilation Line between the reservoir and the transmission body
As a quick note, the dealership cleaned up the the car the day before to inspect in the morning. Upon inspection the next day there was ATF coming out from the top (so I guess it's not the breather on the top). This leaves 2:
- Secondary Oil Pump in the transmission on the right rear
- Ventilation Line between the reservoir and the transmission body
Car those items be services in place?
Yes, see my post #3. If they need part numbers, let me know.
Thank you for your (as always) invaluable input. Sorry I missed #3 and #4 as my laptop did not load them initially! I agree with you that the transmission on those cars would need a complete overhaul (with new and superseded/upgraded parts). Alas, The knowledge (like you stated) does not exist commonly (and definitely not where the car is right now)... so when i send it back stateside, it will need serious work (expect it coming your way!).
Based on my inspection, K1 and K2 were dry, so no issues there. The leak is coming from above the reservoir (top of reservoir is shiny and below is super wet). Could be secondary pump, could be the vent hose to the reservoir or the reservoir itself on its top (broken plastic?), but all above needs to be inspected. I will stop by the dealer tomorrow with a digital endoscope I bought and have them snake it in there to inspect further.
For the vent hose, do you still use 99918116750?
Also the sealing rings (from out to in in that order) would be 1262770855, 0059978448, 0059978548
I hope it is a simple broken tube or/and reservoir.... let's see
Just an update on this. First a big thank you for all the feedbacks received in tracing and addressing this.
Went to the dealership today and we did a detailed inspection and as expected, all the leak was coming from the secondary pump. The center was quite wet and when the car was running it was leaking actively. We did not see any leaks beyond that and the vent hose looked fine (and dirty).
What is the recommendation at this point? just address the leak in the center and leave all else alone for now? Should we drop the exhaust and heat shield to get access or just the reservoir and its shield?
Another update (sitting at home while on lockdown gives a lot of free time to research :-D)
Found details on the secondary pump in the Benz World forums which should be helpful for the dealership. Gonna send the car back in, and i think it would be prudent to redo all the seals on the secondary pump and do it on a bench...
Quick question... The large O-ring seal (7) in the Porsche diagram (0059978548) shows it sitting between the transmission case and the intermediate plate (2) while in the 722.3 manual from MB it shows it sitting between the pump and the intermediate plate. Which one is it? :-D
03-20-2020, 01:15 PM
Transmission Secondary Pump Seal, Overflow Seal and Vent Tube Replacement
