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Discussion Starter #1
Hello again, I have the yellow transmission warning come up, tells me limited gear selection and sometimes it goes away immediately, and sometimes it stays for a while then goes away.
I checked the faults and these are stored:

004F42: SMG: Hydraulic control unit: activation frequency, pressure build-up

004F43: SMG: Hydrauli unit: ON Period

I did a google and read somewhere that the smg pump sound needs to be consistent and then trail off near the end of the cycle - i'm not 100% sure but it seems that i do have this sound.

Any help is appreciated!
 

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Hey guys, had same issue on 2008 SMG
clutch was worn so I replaced flywheel, clutch, fork, TOB, sleeve, pin, and SMG pump motor after RCOD and car wouldn't start.
During installation tech noticed wire harness from SMG unit had no insulation and was grounding to trans case, I panicked because I couldn't afford a $5K SMG unit(harnesses not sold separately)
I got some heat shrink and we disassembled the harness, insulated all 12 wires then wrapping heat tape and re installed.
All was well until about 10 days after, yellow cog started appearing when coming to complete stop between 2nd and 1st gear, in the highway it was smooth and no issues.
Over a few weeks I ignored but it kept getting worse, till the red cog started showing up an shifting was off, no manual selection, hesitate to go in reverse.
Took it back and clutch position sensor failed over 200 times.
Replaced position sensor last week now car still has yellow cog every once in a while, shifts perfect but I'm so fed up with this SMG!!! But I love the car.
technician said it could be the pressure sensor but I'm over it, no more $$$ on this car.
 

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I didn't read where you replaced the slave cylinder while the transmission was out. Too many times we read here where problems arise right after a clutch change and it's due to a bad slave cylinder. It's HIGHLY recommended any time the transmission is removed, all the bell housing parts get replaced including the slave cylinder. The reason is that the transmission has to remove to replace it. Do it all once while it's sitting on the floor.
 

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Discussion Starter #5
Hmm, what is this slave cylinder you speak of... I have to look into this.

Would the slave cylinder cause the smg pump to run more often/longer?
 

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Didn't change the slave, technician didn't recommend it, he has rarely seen them fail, but at this point IDK, only had 1 error message today in heavy traffic, other than that everything else seems fine
 

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Sounds like a leak on the hydraulic block, causing loss of pressure and increased on period of the pump to maintain pressure. I may be wrong but I have experienced this!!


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Discussion Starter #9
Sounds like a leak on the hydraulic block, causing loss of pressure and increased on period of the pump to maintain pressure. I may be wrong but I have experienced this!!


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can you elaborate on this a little? is that an external leak? will you see the trany all wet in hydraulic fluid? or internal?
 

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Sounds like a leak on the hydraulic block, causing loss of pressure and increased on period of the pump to maintain pressure. I may be wrong but I have experienced this!!


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can you elaborate on this a little? is that an external leak? will you see the trany all wet in hydraulic fluid? or internal?
 

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Didn't change the slave, technician didn't recommend it, he has rarely seen them fail, but at this point IDK, only had 1 error message today in heavy traffic, other than that everything else seems fine
They fail a lot and you can't tell by looking at them. Fluid starts to bypass the internal seal and the calibration can't be done after a clutch change. They have also been know to spray hyd fluid all over your new clutch and ruin it. Cheap 300.00 insurance IMO since it has rubber inside that deteriorates over time. It's a wearable part that only be changed when the transmission is out.
 

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can you elaborate on this a little? is that an external leak? will you see the trany all wet in hydraulic fluid? or internal?


Hi

I'm not mechanically savvy but from what I understood it was internal and could not see fluid anywhere.


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Discussion Starter #13
hmm.. i wonder how to check if there is an internal leak or not. what did your mechanics do to fix it?
 

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hmm.. i wonder how to check if there is an internal leak or not. what did your mechanics do to fix it?


They hooked it up with the diagnostic, activated the pump and monitored the pressure which dropped abnormally quick on the SMG pump. It refused to hold pressure as a good working unit normally would.


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Discussion Starter #15
They fail a lot and you can't tell by looking at them. Fluid starts to bypass the internal seal and the calibration can't be done after a clutch change. They have also been know to spray hyd fluid all over your new clutch and ruin it. Cheap 300.00 insurance IMO since it has rubber inside that deteriorates over time. It's a wearable part that only be changed when the transmission is out.
This internal seal is that one of the orings that come with the new pump itself?
I am awaiting my new pump from ecs... hopefully my pressure dropping fast will be resolved with a new pump and seals/o rings.

I checked my pressure and it goes up to about 60bar but then goes down to about 45 within approx 2 min. I imagine this is a internal leak?
 

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My faulty pump would hit 100bar then drop immediately every 5 seconds and hold at 40. The new one hits 100 bar or slightly more and takes a lot of time before dropping in pressure


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This is exactlly what I wanted to hear - so my pump is definetely no good. Too bad ecs just told me to wait till aug 6 for them to get it.
 

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My faulty pump would hit 100bar then drop immediately every 5 seconds and hold at 40. The new one hits 100 bar or slightly more and takes a lot of time before dropping in pressure


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Interested where are you getting this info?

Normal pressure should be 75 bar, max is 90 bar for adaptions and such..

You can see this info in INPA.. From most cars i have seen, while engine running, the pressure drops slowly until around 50's bar where the pump starts up again to bring it back up to mid 70's again.

There is a function in DIS that you can check the hydraulic health of your unit.
SMG accumulator leak down test and SMG pump pressurization time test
 

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Interested where are you getting this info?

Normal pressure should be 75 bar, max is 90 bar for adaptions and such..

You can see this info in INPA.. From most cars i have seen, while engine running, the pressure drops slowly until around 50's bar where the pump starts up again to bring it back up to mid 70's again.

There is a function in DIS that you can check the hydraulic health of your unit.
SMG accumulator leak down test and SMG pump pressurization time test


Hi

Like I said I not at all mechanically handy so I'm just stating what I saw when my car was linked to a diagnostic touch screen and mechanic activated the pump and I heard it prime and could see the pressure figure and how it decreased on the screen.


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Hi

Like I said I not at all mechanically handy so I'm just stating what I saw when my car was linked to a diagnostic touch screen and mechanic activated the pump and I heard it prime and could see the pressure figure and how it decreased on the screen.


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Gotcha, was just interested where you collected the data..
 
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