DCT service PSA: the "Sucking Jet Pump"

[Helmsman]

Originally Posted by DrFerry

I'm not so sure. To me the "Sucking Jet Pump" maybe electrical because the pump body has no obvious mechanical drive. It seems to "plug" into the mechatronix module off to the side. See the male nipple on the end.... Haha.
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Check out p 42 mate: https://www.m3post.com/forums/attach...4&d=1317583307

[tdott]

Originally Posted by DrFerry

Interesting. I would never have guessed that. A vacuum 'pump'. No wonder the words "Sucking Jet Pump" are used to describe it. Thanks.

alot of hydraulic pumps work like this (oil pump, ps pump, etc). They suck from the inlet, the output pressure via the outlet port.

[DrFerry]

Originally Posted by Helmsman

Check out p 42 mate: https://www.m3post.com/forums/attach...4&d=1317583307

Oh wow. I love this file. Thank you so much for sharing it. Excellent resource material on the DCT. Very nice.

[DrFerry]

Originally Posted by tdott

a lot of hydraulic pumps work like this (oil pump, p.s. pump, etc). They suck from the inlet, the output pressure via the outlet port.

Agreed, but those type of pumps are belt driven, gear driven, or shaft driven. No such 'drive' mechanism appeared visible for the "sucking jet pump" on the diagrams I could see. Which is why I erroneously suspected it was an electrical pump. spammysammich 's mention of it being a 'vacuum' pump was in response to this observation.
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https://www.m3post.com/forums/showpo...5&postcount=41

[Helmsman]

Originally Posted by DrFerry

Oh wow. I love this file. Thank you so much for sharing it. Excellent resource material on the DCT. Very nice.

Its nice isn't it! Believe it was Bimmerpost that put it together at some point in early DCT life.

I have a few other bits incl a BMW (work shop) DCT description, only on Swedish paper though...
Trying to understand the box a bit more in order to proceed with my little investigation reg occasional over heat (which quite a few seems to suffer from). Started to log some data with the ProTool (together with Redd) to see if some conclusions can be made which potentially can be of interest to others. Lets see.

[Tibi_M2]

The question is still opened WHAT the hell is this noise Normal / not normal :/

[uhhh_maks]

Originally Posted by Tibi_M2

Dear All,
Just get this thread link from another topic, I'm searching for the reason of this sound what you can hear on the video, the car is an M2 N55 with DCT. Many of the M2's with dct having this sound, but also there is agroup where there is no sound, so it's confusing :/

The issue:
The sound comes ONLY in neutral, and loud only after cold start,
But its coming exactly 7 times in each minutes after 50 sec silence, 7 noise 50 sec silent and so on, if i change to gear 1 or R, the sounds stops immediatelly, and only comes again if i take it back to N, so its kind like expected/programmed. I have NO leaking on my dct, and there was no leaking before as well but ofc i don't know the oil level currently!

Question 1: Cold it be the jet pump?
Question 1: Is this unit electrical? Cause i check all the upper uploaded photos but i can't see any wiring/connection, but the name is still a pump, and pumps mostly electircal units i think!

Thanks for your help / comments

This sounds extremely similar to my noise from my previous comment. I replaced my sucking jet pump and it did not change the noise at all, I am still searching for the answer.

[uhhh_maks]

Originally Posted by DrFerry

Agreed, but those type of pumps are belt driven, gear driven, or shaft driven. No such 'drive' mechanism appeared visible for the "sucking jet pump" on the diagrams I could see. Which is why I erroneously suspected it was an electrical pump. spammysammich 's mention of it being a 'vacuum' pump was in response to this observation.
.
https://www.m3post.com/forums/showpo...5&postcount=41

The sucking jet pump is just a check valve. I cut my old one open (ball was flipped like some pics in the OP), it's a hollow metal ball and spring that pushes the ball against a seal. The orientation is such that it could draw fluid in from the bottom and then not let it run back into the pan.

I blew into the new Getrag part to see how well it sealed compared to my old one and it really doesn't hold much pressure.

[Tibi_M2]

Originally Posted by uhhh_maks

The sucking jet pump is just a check valve. I cut my old one open (ball was flipped like some pics in the OP), it's a hollow metal ball and spring that pushes the ball against a seal. The orientation is such that it could draw fluid in from the bottom and then not let it run back into the pan.

I blew into the new Getrag part to see how well it sealed compared to my old one and it really doesn't hold much pressure.

I just listened your video from previous page, your sound is quite similar, but for me and for some another dudes in m2 club its happening 7 times in one minute with 48 seconds of totally silence and only in neutral, do you have the noise in gear 1 or R?

How many km in the car can i ask?
Did you ask any service?

[deansbimmer]

Originally Posted by Tibi_M2

Dear All,
Just get this thread link from another topic, I'm searching for the reason of this sound what you can hear on the video, the car is an M2 N55 with DCT. Many of the M2's with dct having this sound, but also there is agroup where there is no sound, so it's confusing :/

The issue:
The sound comes ONLY in neutral, and loud only after cold start,
But its coming exactly 7 times in each minutes after 50 sec silence, 7 noise 50 sec silent and so on, if i change to gear 1 or R, the sounds stops immediatelly, and only comes again if i take it back to N, so its kind like expected/programmed. I have NO leaking on my dct, and there was no leaking before as well but ofc i don't know the oil level currently!
Thanks for your help / comments

The sound seems more like a harmonic vibration or heat shield. Once the sound starts, try holding a different RPM to see if the sound continues or ceases. There are no electrical motors in the DCT vicinity.

The sucking jet pump is a venturi pump. It has a check valve to prevent backflow but also to maintain correct flow direction. The small nipple in the side of the sucking jet pump is the higher pressure oil flow circuit that creates the venturi "sucking" action in the sump. The check valve prevents backflow and keeps the circuits full of fluid.

[DrFerry]

Originally Posted by uhhh_maks

The sucking jet pump is just a check valve. I cut my old one open (ball was flipped like some pics in the OP), it's a hollow metal ball and spring that pushes the ball against a seal. The orientation is such that it could draw fluid in from the bottom and then not let it run back into the pan.

I blew into the new Getrag part to see how well it sealed compared to my old one and it really doesn't hold much pressure.

So not really a 'pump' after all, but a venturi instead, and no drive mechanism such as vacuum, a gear, a belt, a shaft nor electric. Got it. Thanks.

[Tibi_M2]

Since it's not electrical then I think and where was a case when the pump change solves nothing, i started to think that it's not coming from the dtc, but what else dould it be, it's for sure a pump something behind the engine or above the dct :/

[Assimilator1]

Originally Posted by Tibi_M2

Since it's not electrical then I think and where was a case when the pump change solves nothing, i started to think that it's not coming from the DCT, but what else could it be, it's for sure a pump something behind the engine or above the dct :/

Did you see Deansbimmer reply?

[Tibi_M2]

Originally Posted by Assimilator1

Did you see Deansbimmer reply?

Yes i saw, i will check it for sure, i will see the car again in marc 8. im now in a different location

[chocstraw]

Originally Posted by Bimmer Barney

deansbimmer any references for shops in CA that can do this service as you’ve described? Maybe MRF?

No need for a special shop. Print this out, supply parts 4, 6, 8, and maybe a new pan— they'll be fine. This is not a hard job and BMWs have had the same fill procedure for ATs for a couple decades now. The fill procedure is also not as sensitive as the literature claims. Just pin it for ~60 seconds at 2k when it's cold and you're fine.

~

Small aside, my $1000 used trans was in flawless condition, doesn't leak, and took the opportunity to re-do all the seals and small parts anyways. Parts yard owner just wanted it gone and I got lucky. Upon removal, I found out that the shaft that connects to the driveshaft broke on the old trans. I have yet to hear of this failure and cannot imagine how it happened. These transmissions are super robust, normally, and I launched mine maybe 10 times total.

[uhhh_maks]

This thread has gotten a bit off topic but I figured I'd update on my situation. I dropped the pan again this evening to find that the o-ring at the top of the suction filter rolled out of its groove upon installation. Easily avoidable mistake as you can see all the way around the seal if you crawl around a bit. Luckily the bore it sits in has a hefty chamfer, so the seal was still in fine condition.

I also had actually been trying the URO cast aluminum pan that Hivand mentioned earlier in the thread:

Originally Posted by Hivand_M

A bit off topic but anyone try below DCT oil pan? Seems like a carbon copy of the OEM one but made in aluminum and is a bit cheaper, $156 vs $183 for OE.

https://www.fcpeuro.com/products/bmw...ts-28108070791
...

but it was weeping fluid at the back so I returned it and got a Getrag pan to replace it. I would advise against the cast pan, it had a lot of flash and sharp edges left over from manufacturing, and the seal is a different design that did not seem to want to seal. I also think the metallic pan may have amplified the noise, some searches led me to other threads linking metal pans and weird DCT noises.

After reinstalling and refilling with the OEM pan, the sound was still there but was much quieter while laying under the running car.

With the undertray installed and the car on the ground I could barely hear it, making me question whether I just didn't notice it before my initial service, and the combo of the slipped o-ring and aluminum pan amplified it.

Either way, at this point I have checked and rechecked everything I could so I'm going to try to move on with my life and will keep and ear out for any change.

[Tibi_M2]

Originally Posted by uhhh_maks

This thread has gotten a bit off topic but I figured I'd update on my situation. I dropped the pan again this evening to find that the o-ring at the top of the suction filter rolled out of its groove upon installation. Easily avoidable mistake as you can see all the way around the seal if you crawl around a bit. Luckily the bore it sits in has a hefty chamfer, so the seal was still in fine condition.

I also had actually been trying the URO cast aluminum pan that Hivand mentioned earlier in the thread:

but it was weeping fluid at the back so I returned it and got a Getrag pan to replace it. I would advise against the cast pan, it had a lot of flash and sharp edges left over from manufacturing, and the seal is a different design that did not seem to want to seal. I also think the metallic pan may have amplified the noise, some searches led me to other threads linking metal pans and weird DCT noises.

After reinstalling and refilling with the OEM pan, the sound was still there but was much quieter while laying under the running car.

With the undertray installed and the car on the ground I could barely hear it, making me question whether I just didn't notice it before my initial service, and the combo of the slipped o-ring and aluminum pan amplified it.

Either way, at this point I have checked and rechecked everything I could so I'm going to try to move on with my life and will keep and ear out for any change.

Dear uhhh_maks

So you think the basic solution is to change the o-ring? Can you please upload some photo which o ring is this, or just add here the OEM number
You would help a lot since i have the same sound but not that often You have it, i have 7 times each 48 seconds! And only in neutral. Would you be so kind to check, do you have it also in 1 or R?

Thank you mate !!!!!!!!!!

[uhhh_maks]

Originally Posted by Tibi_M2

Dear uhhh_maks

So you think the basic solution is to change the o-ring? Can you please upload some photo which o ring is this, or just add here the OEM number
You would help a lot since i have the same sound but not that often You have it, i have 7 times each 48 seconds! And only in neutral. Would you be so kind to check, do you have it also in 1 or R?

Thank you mate !!!!!!!!!!

If you haven't done a transmission service ever, I would recommend that. The o-ring was part of the filter: https://www.fcpeuro.com/products/bmw...ag-28107850148

I didn't measure the size unfortunately.

I just checked and it only happens in neutral. The noise stops as soon as I press the brake pedal. I can definitely still hear it but it is very faint with the car all buttoned up.

[Tibi_M2]

Originally Posted by uhhh_maks

If you haven't done a transmission service ever, I would recommend that. The o-ring was part of the filter: https://www.fcpeuro.com/products/bmw...ag-28107850148

I didn't measure the size unfortunately.

I just checked and it only happens in neutral. The noise stops as soon as I press the brake pedal. I can definitely still hear it but it is very faint with the car all buttoned up.

Because of the netural thing then we sure have the same thing, but the break thing is new for me, i will do an oil service for sure, this o ring is coming with the new pan right thats good, so I don't need to search for it separately!

If the break also stops the noise, it could be also some break related thing? Or You 100% sure its the DCT?

Thanks

[uhhh_maks]

Originally Posted by Tibi_M2

Because of the netural thing then we sure have the same thing, but the break thing is new for me, i will do an oil service for sure, this o ring is coming with the new pan right thats good, so I don't need to search for it separately!

If the break also stops the noise, it could be also some break related thing? Or You 100% sure its the DCT?

Thanks

If I lay under the car I can feel the noise very clearly with my hand on the transmission pan, so I'm 99.9% sure its the DCT.

The only thing I can think about regarding the brake is that the car is assuming you're about to shift into gear so it does something to prepare?

[Tibi_M2]

Originally Posted by uhhh_maks

If I lay under the car I can feel the noise very clearly with my hand on the transmission pan, so I'm 99.9% sure its the DCT.

The only thing I can think about regarding the brake is that the car is assuming you're about to shift into gear so it does something to prepare?

The idea of the braeak sounds reasonable.

So just to summarize:
- Is this sucking thing is happening in all DCT, just another dct has no loud noise together with it?

- Have you ever checked any other dct where at least its possible to feel on the dct with hand as you wrote, but no stupid noise with it?

- What I'm thinking about, that maybe it's a software or a sensor issue? and normally this should not happen in neutral, just only driving, cause it's so crazy that many people never ever hear it.

- Basically the noise is done by the jet pump or the failed suction because of the old sealing, what you think is more logical?

And again thanks for your thoughts

[uhhh_maks]

Originally Posted by Tibi_M2

The idea of the braeak sounds reasonable.

So just to summarize:
- Is this sucking thing is happening in all DCT, just another dct has no loud noise together with it?

- Have you ever checked any other dct where at least its possible to feel on the dct with hand as you wrote, but no stupid noise with it?

- What I'm thinking about, that maybe it's a software or a sensor issue? and normally this should not happen in neutral, just only driving, cause it's so crazy that many people never ever hear it.

- Basically the noise is done by the jet pump or the failed suction because of the old sealing, what you think is more logical?

And again thanks for your thoughts

- I have no idea
- I have not
- Again not sure, it's clear the noise is controlled by software or something given the rhythm that it happens
- For my car, it was pretty clear that the noise was made much louder when the oring was not seated properly