W124 Auto Transmission Secondary Oil Pump Seal

1986-1995 : 200TD, 200CE, E200, 260E, 300E 2.6, 300E 2.8, 300E, E320, 400E, E420, 500E, E500, 300CE, E320, 230TE, 300TE, 300D 2.5 TURBO, E300 DIESEL, 300TD, 300E 4MATIC, 300TE 4MATIC, E36 AMG
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Christo C
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W124 Auto Transmission Secondary Oil Pump Seal

Post by Christo C » Mon 02 Jul, 2018 3:17 pm

This is a 1986 230E sedan, W124 with a 722.408 Auto Transmission

After a lot of cleaning and investigation I traced an Auto Transmission Oil leak to the Secondary Oil Pump, which is mounted at the driver's side rear of the transmission, up high, opposite the Centrifugal Governor.
RearPump1.png
Most of the leak seemed to come from the pump's Closing Cover (27), so I managed to obtain a replacement O-Ring (29, Part 016-997-37-48), and with some difficulty removed the Circlip (28) & Cover and replaced the seal. Was done on a hoist, and the tricky part was reinstalling the Circlip, as there was spring tension on the Closing Cover. Surprisingly very little Transmission Oil leaked out during that struggle.

Well, that cured around 90% of the leak.

It now seems the rear seal O-Ring (18, Part 016-997-32-48) for the pump body has to be replaced.

It 'looks' easy enough to me, given that the pump's location is a little awkward and the procedure may be quite fiddly, involving a lot of feeling around and use of mirrors to check the new O-Ring is settled into place before re-inserting the Pump body. Also, I assume I will have to be very careful that the pump gears are aligned exactly as they were when removed to mate with whatever they mate with at the rear of the Centrifugal Governor. I am not keen to drop the Transmission as there's nothing else wrong with it at the moment....

So I am wondering if anyone else has tried this in-situ?

Any advice?
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Last edited by Christo C on Fri 13 Jul, 2018 9:28 am, edited 2 times in total.
~Christo
1986 230E W124.023 M102.982 ~290,000km Thistle Green Saloon "Janis"

Henry Schuman
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Henry Schuman » Fri 13 Jul, 2018 8:22 am

Keep in mind it has been a few years since I built one of these trany's but Here Goes.
As I recall you CAN replace that particular #30 Seal without removing the pump and IF I remember the seal is a Split TEFLON Ring and you need to put it in place on that little valve then put the valve in your Freezer for an hour or so so it will shrink allowing you to put it back then fiddle with the spring cap and retainer and your good to go . IMHO # 30 Rarely leaks but I think # 29 in your photo is a Rubber O Ring that is Recessed in the Housing where the Metal cap goes then the Retainer . Now that gets hardened over time and will seep fluid . Normally if one of the Teflon seals are bad it will leak under pressure and you would have a lot of fluid pissin out .
Like I said it's been a while.

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Christo C
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Christo C » Fri 13 Jul, 2018 8:50 am

Thanks Henry.
Sorry, My bad, you are correct, yes it is definitely #29 that is the seal (rubber O-ring Part # 016-997-37-48) for the Cover, and I did manage to replace it and the leak was reduced by well over 95% to a mere occasional drip or weep, rather than a river.
It is the rear seal (of the Pump Body) #18 that is of interest now - as I can find ATF seeping from around the rear of the pump - do you reckon I could remove the pump body (no need to touch the front cover and little valve again) and replace O-ring #18 in situ without much difficulty?

PS I fixed the drawing in my original post !
Last edited by Christo C on Fri 13 Jul, 2018 8:59 am, edited 1 time in total.
~Christo
1986 230E W124.023 M102.982 ~290,000km Thistle Green Saloon "Janis"

Henry Schuman
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Posts: 24
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Henry Schuman » Fri 13 Jul, 2018 8:59 am

Well I think 18 is a Rubber O Ring and it goes around the Pump Housing so yep you can replace it too.
Most of the Time you will find that as you replace one then another starts leaking somewhere else ,either outside or inside and you will be Chasing your tail so to speak here on in . Heat and Fluid breakdown over the Years cause all the Rubber seals in the Trany to harden and sooner or later they will start leaking .
They make a product here in the States Called Trans X and while I don't usually recommend Snake Oils for Repairs this Product does work and I have used it for many years in situations like yours. It actually softens those hardened Rubber Seals and gives you a little more time to go on down the road.
Last edited by Henry Schuman on Fri 13 Jul, 2018 9:08 am, edited 1 time in total.

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Christo C
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Christo C » Fri 13 Jul, 2018 9:01 am

Should be back now... refresh your webpage?
~Christo
1986 230E W124.023 M102.982 ~290,000km Thistle Green Saloon "Janis"

Henry Schuman
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Henry Schuman » Fri 13 Jul, 2018 9:09 am

Got it.

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Christo C
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Re: W124 Auto Transmission Secondary Oil Pump Seal

Post by Christo C » Sun 15 Jul, 2018 9:49 am

Hmm, I just found this useful site, for a slightly different/earlier 722 transmission, but the parts all look the same:

http://www.benzworld.org/forums/w124-e- ... eseal.html

Looks like I have to be very careful re orientation of the "...threaded shaft with a nut on it. A slot in the end of that shaft must be properly oriented to avoid badness...." where the "badness" appears to be destruction of the transmission. Ouch!

and this

http://www.benzworld.org/forums/w126-s- ... -seal.html
and
http://www.benzworld.org/forums/w126-s- ... eal-2.html

where they mention "The pump is almost impossible to get out without dropping the transmission. It's just too tight in there! ..."

so I may shelve this little project for a while... or see if the local transmission specialist will look at it.
~Christo
1986 230E W124.023 M102.982 ~290,000km Thistle Green Saloon "Janis"

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