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Discussion Starter #1 (Edited)
Hey guys, late summer my clutch started slipping under power sporadically, so I figured it must be the throwout bearing, seems i was right as mine has severe wear on its inner bore and it jams up really easily. the clutch itself looks like it's still got tons of life left but I'll replace it and the flywheel anyway, the flywheel has quite a bit of play in it.

A little info about the car, it's a 2006 (12/05 build) 115k miles.

But while I was in there I decided to pull SMG hydraulics apart and replace any o-rings/seals I could find. I went through, measured the sizes of the o-rings and seems like I can find viton ones on mcmaster for all of them except I can't find the piston seals for the selector rods. Anyone know a source for these? I inspected mine and they don't look to be worn but I figure if I can source them for a decent price might as well.

I'm referring to these guys



And now some pictures of what I found inside:

Looks like at some point in the past water had gotten in behind my pump motor


also the motor hub has a ton of wear in it, so I'll have to make a new one


not sure why there was only rust where the hub adapter goes since the rest of the motor face was clean


looks like there was a ton of wear on the motor shaft, and the shaft wasn't fully engaged, i'm guessing getrag made the coupler a little under-size, I will likely make a custom one that's a bit longer


slave cylinder dust boot was fully torn off, looks like these aren't serviceable so I'll have to get a new one


tons of wear on the throwout bearing


but the clutch disks and the pressure plate look like they're in great shape, other than a bit of galling



it's crazy how poor machining quality is on these components, but i guess they're ok enough as at least the o-rings between the shifter valve block and the piston block didn't seem to be leaking, but the shifter block was leaking against the transmission, i had tons of mtl leaking around the top




and here's the scary bit, I need to replace the wires on the shift rod position sensor, but mine has cracks in it, so i'm hoping it doesn't break while i'm working on it (it was working fine when i removed the gearbox). I will likely try to seal it up with potting compound or some sort of RTV once it's back in position so water doesn't try to get into the cracks



btw, how does the accumulator work? at the bottom of the input hole it's blocked off, or are there small holes leading to sideways?


looks like this car had that clutch pressure plate failure where the spacer pucks fall out and start flinging around the bell housing


I'm going to try to document this project here, and I absolutely welcome any advice, except for "don't do this if you don't know what you're doing" :grin

here's a link to the whole image gallery https://drive.google.com/open?id=13g2j4tH2S2NevpalVYfVP-e-prcEH9eo
 

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Discussion Starter #2
Is it worth replacing the hydraulic accumulator, mine seems to work still but I did notice that my pressure bleeds off much faster than it used to.

When I got the car 5 years ago (87k miles) the SMG pressure test would end at around 41bar, now it'll barely pass at 31.

I'm assuming it's mostly due to the clutch solenoid leaking down, hopefully replacing its o-rings will help. But maybe it's also due to the accumulator no longer storing as much pressure due to preload leakage?
 

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Jim has mentioned in the past that he had to get custom dies made for the piston and pump internal orings and would not sell them for this reason. But ask nicely anyway? The pump internal oring can also be found on ebay from china I believe - but I'd be cautious with this. The torque spec for the pump screws is not available, and I would question the quality of the ebay oring. No other known supliers at the moment.

Yes the motor coupler has some play built into it to allow for thermal expansion and misalignment and what else. Yours look better than mine with 80k miles btw.

I also had ‘rust’ as you called it. It's probably a mixture of dry grease and coupler shavings – not rust per se.

The throwout bearing was updated to delrin to prevent galling. Rockauto has good if not the best prices for a flywheel (luk) and clutch kit (also luk – you’ll get a sachs clutch in a luk box, includes an alignment tool and pilot bearing).

I didn’t have any MTL leaking on top of the trans, and never seen pics of leaking like yours. Doesn’t matter you’ll get it fixed now :).

The accumulator is nothing but a high pressure balloon and a piston separating it from the fluid. You’re seeing the piston face. It’s pushed in by the fluid. No I would not change it. Even if pre-pressure is low it works just fine. And if you decide to change it it’s easy to do from underneath the car. Yes pressure bleeding has nothing to do with the accumulator but leakage on the clutch solenoid orings or solenoid itself.

Easiest way to fix the position sensor wires is to un-pin the connector end and use heat-shrink tubing on each wire. I went crazy on mine and used mil-spec wire, potting compound, etc. If I were to do it again I’d just go with good quality heat-shrink tubing.

Now is the perfect time to open the pump motor and clean all the carbon dust inside. The brushes have some stampings that end up preventing them from sliding freely. Scrape the stampings using a flat screwdriver to ensure brushes slide freely. Dust and brushes catching on their holder seem to be the common failure and not bearing failure or brush wear. Be sure to mark the motor ends with respect to the main body with a sharpie before opening.

Here’s my list of stuff to do when pulling a trans – hope it helps.

https://www.m5board.com/vbulletin/e63-bmw-m6-forum-bmw-m6-convertible-m6board-com/578106-smg-problems-need-help.html#post7536564
 

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Discussion Starter #4 (Edited)
Thanks for the information.

I sent jcolley a PM but I haven't heard back yet.

When you did yours, did you replace your shift fork piston seals?

I actually got a hold on a brand new smg pump motor. As for the bushing, my bushing is like 2mm too short, that's way too much for expansion, also once it wears, I dont' think any expansion can occur since the motor and the pump kind of bite into their little groove and that's it, mine was almost solid, i had to pull pretty hard to get it off the pump. I'm going to custom make one that's about a mm longer, should bite on the motor a bit better.

I also had ‘rust’ as you called it. It's probably a mixture of dry grease and coupler shavings – not rust per se.
You're probably right, upon closer inspection last night I noticed it's almost got the consistency of graphite. but looks like the new motor kits come with a white lithium grease, probably with PTFE, so I guess i'll just go with that when I repack it.

Easiest way to fix the position sensor wires is to un-pin the connector end and use heat-shrink tubing on each wire. I went crazy on mine and used mil-spec wire, potting compound, etc. If I were to do it again I’d just go with good quality heat-shrink tubing.
that's a good idea, I might just go this route.

As for the updated throwout bearing with the delrin liner, they're installed totally dry, right?
 

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Discussion Starter #5 (Edited)
oh, wow, thanks for the tip to look on rockauto, their prices on this stuff are WAY lower than everyone else i saw. I was originally going to try to get them from FCP but, not at that premium.

It's too bad they don't carry some of the other stuff I need, like the bearing sleeve or slave cylinder.
 

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Discussion Starter #7
So I ended up going a different route as far as acquiring the rebuild/refurb kit.

I randomly found a company (https://mlreng.com/) via ebay which sold an SMG pump motor kit and shot em off a message asking if they were able to sell me just the seal set for the pump since I had randomly already bought just the motor itself, without any of the other parts.

I was very surprised to find that not only did the guys sell the parts separately, BUT they actually had all the rest of the seals for the whole SMG hydraulic unit. So I went ahead and purchased a complete kit from them and it has just arrived on monday! The kit looks really well put together, super easy to figure out what o-ring is for what purpose, etc.

The kit I bought from them included the all parts from the SMG pump kit, all the o-rings from the shift solenoid block (including all of solenoid o-rings) and the clutch solenoid o-rings.

I haven't had a chance to start the rebuild, when I do I'll post detailed photos of the kit and all of the process itself.

PS: I was originally going to buy all the o-rings from mcmaster, but they didn't actually have exact sizes for some of the o-rings I needed, so that's why I decided to just get a pre-made kit.
 

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Discussion Starter #8
A quick question for those who have done this before, what would you recommend I used to wash the aluminum parts and solenoids in (I'm going to use a parts washer and some soft nylon brushes)?

I was thinking of using water and dish soap since that shouldn't etch the aluminum bores, but I'm not certain that's the best thing for the job.
 

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Discussion Starter #10 (Edited)
Here are some pictures of the kit provided by http://MLReng.com:

In this photo are the items which are part of the SMG motor pack, I got just the hardware kit since I already had the motor. very nicely organized.


In this photo are the nicely packed o-rings for the hydraulic shifter unit (on top of the gearbox) it came with every single o-ring to do the job, including all of the solenoids and 8 shifter piston block o-rings, as well as the seals for the shift position sensor.
At the top is a prototype replacement wiring harness for the shift sensor, since this is a prototype it's all the same color and the wires are a bit stiffer than stock but they're very high quality, the real one will likely be modified a bunch, but this one worked for me perfectly as is. the insulation on these wires was VERY strong, and it comes with the whole connector pre-assembled.



Here are some close up shots of the replacement wiring harness





 

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Discussion Starter #11 (Edited)
Alright, so I've gone through and reassembled the whole SMG hydraulic unit and bolted it all up to the car so here i'm going to post all my findings and info I found in the process. This is not really a DIY guide since it skips a ton of steps but I'm laying out steps which I found to be a bit of a gotcha.

As mentioned in the previous post I used an O-ring and seal kit I purchased from http://MLReng.com. They normally only sell the SMG pump motor kit, but I emailed them and they also were able to provide the o-rings for the shifter hydraulic unit as well.

So first off I purchased a brand new parts washer from harbor freight for this job since my old one was really dirty and I was afraid i'd pump some junk into the parts while washing them.

I did a bunch of research regarding what soap would be good to use and ended up using Simple Green, looks like it's even recommended for washing airplanes and airplane parts so it's totally safe on aluminum, shouldn't etch it even if left on for a little while. But it shouldn't be anyhow, since after washing the parts in the washer with some tube brushes I immediately went over to my sink and rinsed them with hot (as hot as wouldn't burn my hands) water then I went over to my garage and blew the parts dry with shop air (filtered). Since I wasn't replacing the actual shifter piston seals I decided it's best not to wash or even touch the seals, so I simply removed and gently poured fresh chf-11s on them just to rinse off any dirt, and just washed the 2 chambers they slide into. When you remove the pistons keep in mind they are directional (or at least they aren't symmetrical). Take note of the shape when you remove them and reinstall in the same orientation.

Also I decided it's best not to wash the actual solenoids in case water got into it and I wasn't able to fully dry it out, in retrospect I maybe should've but I didn't.

At this point everything was reassembled using all new o-rings, I highly recommend using a plastic toothpick to remove the o-rings from the solenoids so as not to scratch the o-ring grooves! Also fully lubricate all the o-rings as you slip them on the solenoids and it's also a lot easier if you start from the smallest to largest o-ring, that way the larger o-ring won't get stuck in the small o-ring's groove. Then just before pushing the solenoids back in don't forget to reinstall the shifter position sensor before putting the 2 rear solenoids (it goes under them), here's what mine looked like after soldering on the new wiring harness, I used some raychem heatshrink on mine, also the wire insulation coming right out of the unit totally fell apart so the very base of the wire was still exposed so I slathered them in some conformal coating and then silicone RTV to make sure no water gets in there.



Just before installing the solenoids apply some of the grease provided and carefully pop them in by applying even force, mine went in with maybe 10-20lbs of pressure, then use some loctite blue 242 or similar threadlocker (I used this stuff from amazon) on the little torx head screws before bolting them in.

Next step is to install the shift pistons, lube the inside of the pistons tubes and dip the pistons themselves in some fresh CHF-11S and carefully slide them in, then position all 12 o-rings labeled "Shift Cylinder" in my kit (4 larger ones for the shift position sensor and 8 small ones for the piston block) and reinstall the piston block in the same orientation as it came off.
Again use some of the blue loctite on the 12 torx bolts which secure down the piston block as you screw them down.

Before sliding the shift piston block onto the transmission don't forget to make sure all the pistons positioned such that the middle cutout is in between the 2 blocks and rotated around such that the notch is facing down like in the following picture:


Then put a coat of RTV on the sealing face following around the outside of the screw holes and inside of the alignment pins and press the block onto the transmission again using blue loctite on the bolts.
 

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Discussion Starter #13 (Edited)
Having assembled and bled the clutch I'm actually having a weird issue. I ran the clutch bleed procedure like 10x+ and was able to shift into all the gears manually via the ecu menu but for some reason I'm not able to perform the actuator bleeding procedure. It starts I hear the pump priming, pause then prime again for a little while then rheingold tells me that the procedure has been cancelled.



The bleed procedure ran once, all the way, but when I went to run it a 2nd time It's been doing that every time.

I've checked the pressures, after running the pump via manual actuation a couple times the pressures build up to 80bar, so looks like it's pressurizing just fine.

I am also able to teach in clutch and shift valves just fine, just not bleed. Anyone know what could cause this?

Thanks.
 

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Discussion Starter #16
Sorry about the pics, not sure what happened, they worked last night, I changed the way i'm embedding them so this should work now.

Unfortunately I can't edit the first post's pictures. The edit button is missing. Maybe a moderator can unlock it for me so I can fix those images too.
 

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Discussion Starter #18 (Edited)
Yeah I think I recall seeing them. In any case they are still not working...
Really? You can't see pics from any of the posts? I just checked in incognito mode and they all show up except for a few from the first post which I can't edit.

Hm, I wonder what's up. I might have to move them someplace else instead of google drive.

Edit:
Oops, nevermind, I just realized you meant the 2 images in post 11, i forgot to update those earlier
 

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Discussion Starter #20
Always wondered if it’s possible to install a hydraulic throw out bearing on the SMG
Possible you think ?
If you engineered a custom one that had a position sensor (PLCD) which electronically matched the existing PLCD and could bolt on instead of the throw out bearing bushing and also had an operating pressure of around 40-100bar (not sure what normal pedal operated slave cylinders operate at, i'm guessing way less than 60bar) then I don't see why it wouldn't work.
 
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