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Discussion Starter #1
After hours and hours of trying, for some reason my pump will not do anything with the reservoir attached. The motor will turn and turn and turn, but not suck up any of the chf if I attach the reservoir. If I manually use a transfer pump and put the hose line into the inlet on the gear pump, I can push fluid in it with the motor running and it will build pressure.


I did take the gear pump assembly apart when I had it out of the system to check the seals. The seals looked fine so I did not replace the seals on the gear pump assembly. I guess, I am wondering if it a broken seal in the gear pump assembly would prevent the system from sucking up/priming fluid (assuming so).


O-ring were all replaced with MLR's kit. Coupler is seated as indicated by it building pressure when I manually push fluid into the inlet with a pump. Voltage at the motor is good. I simply cannot get it to suck up fluid from the reservoir.

Anyone have any suggestions?
 

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Lots of info here,
Loosening the plug in the bottom to bleed air out would be my first piece of advice.
 

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Are you using software(INPA/ISTA) to run the pump and watch the pressure? I had trouble bleeding mine and the problem was the coupling was bound up and the pump/motor was not turning.
 

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Discussion Starter #6
I have used both. I can build pressure if I manually push fluid into with a pump or transfer deice with a little pressure. Pressure builds up to 40-70 bar quickly and will hold, but when running any bleeding or adaptations, the pressure will drop to 0 and the pump wont suck up more fluid from the reservoir to complete the process.
 

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The reservoir itself may be the problem? I'm trying to remember how it is laid out, it is a sealed unit with the fill plug and suction tube. Not sure what's inside?
 

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Discussion Starter #8
I did not have the plug up top in it when I tried though. Wonder if that lack of suction caused it to not take up fluid?
 

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Reservoir has a vent on top so it's not fully sealed. You could just remove the fill plug and see if that helps (shouldn't if vented). Someone else had a similar problem. Seems the obvious things haven been covered: open drain plug, run motor, make sure coupler is installed properly. Once the pump is full of fluid any further running will cause it to suck fluid. Not sure what the problem could be...
 

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Discussion Starter #10
The vent is covered with a rubber piece, but even with the fill hole open it wouldn't take up fluid.

The pump had 2007 on it, so I am assuming I am the first person in there. THe car is a 2008.
 

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Discussion Starter #11
After pondering on this problem and the processes I used to remove the pump, I am wondering if I did something wrong.

I did reduce hydraulic pressure in INPA and then I also bleed the clutch slave. However, when I bled the hydraulic pressure I loosened the drain where the check valve is (I am assuming there is a check valve there) in an effort to get all the pressure out. When loosening I actually took the plug out, so I am guessing that is not a good thing.

I am able to forcibly push fluid into the pump and it will eventually take and build pressure, but when I try to install the reservoir it will not pull any fluid in. It is like it takes me putting pressure into the inlet for the pump to suck up fluid.
 

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When you opened the drain bolt, were there any fluids dropping out of drain point during the bleeding process?
 

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Did you make sure the motor coupling was aligned to the pump correctly? If not that will prevent the pump from turning.


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Discussion Starter #15
It builds pressure when I push fluid in the inlet (with a transfer pump). It will not take up fluid from the reservoir.
 

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Interesting, do you think you can try perhaps by having rear of the car jack up higher than the front that way the whole fluids flow downward against the pump to allow for a better suction while the reservoir is attached? I think the problem is the reservoir is not seat correctly between the pump anyhow if you pushed fluid in the inlet with a transfer pump and the system build pressure just like that which is why I am inclined to think the problem lay between the hydraulic pump and reservoir that something are not correctly seat or perhaps something inside the reservoir is broken because the last time I looked inside the reservoir, it looks so busy in there, there is a shape then there is a slope then there is a wing for the pump inlet. I thought it was just a simple round empty inside that act as a container but apparently not. it's possible something is broken inside that doesn't allow suction. I have tried jack up the back of the car before but that doesn't work for me, perhaps you could try that. Anyway, what prompted you to touch the SMG transmission in the first place?
 

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No.

I don’t think it had any relevant whether or not if the transmission is lower or in its fixed position because the reservoir is full when you filled it with CHF-11s. The pump should have adequate power to pull fluids into the block. What happened if your car is driving up the hill? I am fairly certain Bmw takes that condition into account to designed the pump in such a way that the pump has adequate power to pull fluid in the block even if the car is positioned upward. Even so, I had the transmission lower before and the car was able to build pressure anyhow.

I rmemeber when I messed with the transmission. To be clear, I had this car since 45,000 miles and now it has 130,000 miles.

The transmission has been fine until about 120,xxx something. It was the point when I decided performed preventative maintenance to the transmission by changing fluids and etc. After that, I begun to have transmission issue specifically smg transmission issue. The first failure was o-rings related even though the problem was not definitive initially with code of 4F43 which brings me to the point of replacing parts, one by one because the present code 4F43 can mean anything, Relay to the most expensive parts of the transmission and the second failure is unknown with similar code of 4F43.

the difference between these twos faults is that the system can build pressure even if there is a leak in system but it’s not the case with the second fault. See what I mean? 4F43 can means literally anything.

I have seen claimed that replacing pressure sensor fixed no pressure issue but then I read another claim that replacing TCU correct the problem but I have seen another claim that replacing the whole hydraulic unit which is $8,000 remedy no pressure issue. The popular claims are to unbolt the check valve to relief pressure inside the block.. Issue like this is seemingly a lucky draw.
 

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Discussion Starter #20
Well I brought the reservoir into the garage to inspect it. Needless to say, its a lot more complex inside than a simple fluid tank.

I did use some compressed air to make sure nothing was clogged, but even after that and some testing inside I don't know how the thing works other than the obvious. Seem like the slat separating L/R is pretty much useless as fluid comes from underneath it. I am not sure if this is intended to keep fluid from sloshing when stopping or pulling out? I am at a loss and about to buy a used unit. You having any luck ?
 
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