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Discussion Starter #1
While working on the hydraulic unit of my SMG, one of the crush washers for the pressure supply line to the unit was inadvertently lost. No big deal, I'll get another one... Except that upon looking up the part #, a replacement crush washer (23017838941) is $80. Yeah... A $0.50 washer being sold for $80.

So, I went to my local BMW dealer and asked for a replacement without giving the part # (because who tf would pay $80 for a crush washer??) and the guy brought back a part that pretty closely resembles the original.. same thickness (~1.375 mm), same inner diameter (~12 mm + clearance), but the outer diameter is a little smaller. I don't remember what the exact number was on the OD, but it was enough to tell visually... maybe 0.5 mm. So, I installed it. Seems ok.

However, the original washer is pretty much exactly the same as the copper crush washers for the oil drain plugs... the only difference being that the material is different.

Does anyone have any suggestions regarding using the slightly smaller washer vs using one that's the same as original, but made of copper instead?

I've heard that copper is actually better for sealing, but other materials are sometimes used in certain areas because they're more forgiving to over-torque. Not sure if the SMG washers are aluminum or some kind of plated steel, but I'm guessing aluminum.

935158
 

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I'm curious about this too. I noticed also that they seem to be aluminum, I never planned to replace them with aluminum ones either, I was planning on using copper. Copper is more malleable than aluminum, but more expensive of a material. $80 is absurd. Absent other special reasons or some special piece of knowledge, the only reason for the washers is to ensure a tight seal for this high pressure hydraulic line. Copper washers in banjo bolts applications are used all the time.
 

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Discussion Starter #3
Sounds to me like it's insurance against a shop worker over torquing the banjo on soft copper in a difficult to reach area. Over torque a copper washer on a drain plug and that's an easy fix. Over torque it on the SMG and now you're looking at removing exhaust, shields, and disconnecting the driveshaft to lower the transmission enough to get to it. Then you're running through a full adaptation for the SMG after replacing it.
 

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Discussion Starter #4
I don't think there's any problem with the replacement washer I used, though. If anything, there will be more pressure applied due to the slightly smaller surface area of the washer. And I'm also thinking that, perhaps, the slightly smaller washer was a purposeful design change meant for a seal that applies more pressure.
 

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Aluminum is cheaper and does not create a potential difference between the metals. I have reused hundreds of these in my work and have had very few problems.
 

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I went through the same thing when replacing my power steering pump and the two crush washers on the high pressure line connected to it. I bought a copper assorted crush washer kit on amazon then ended up just going to the dealer and buying two crush washers at 3.5 each (was cheaper at ecs tuning but didn’t want to wait). On my first install with the aluminum it leaked a lot even though I tightened it pretty good. I then tightened it as much as I could given the space confinement and it no longer leaks. After researching online everyone says the aluminum does a better job at bending/sealing then the copper. For my if this leaks down the road it’s a 2-3 hour job I didn’t want to take that chance. I think your fine in the diameter if it’s not leaking but I would stick with aluminum.
 

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Discussion Starter #7
@x5m5 out of curiosity, what happened with your power steering rack? I recently removed my tie rods from the steering rack in preparation to remove the oil pan for rod bearing replacement. While I was removing the tie rods, a few drops of hydraulic fluid dripped on the floor. Worried that I had just caused a leak in the rack, I tried to move the steering wheel back and forth to get more fluid to leak, but could get any more to come out.

I'm hoping maybe I just temporarily caused a banjo connection to leak and there's no crack or anything internal going on inside the casting.
 

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@x5m5 out of curiosity, what happened with your power steering rack? I recently removed my tie rods from the steering rack in preparation to remove the oil pan for rod bearing replacement. While I was removing the tie rods, a few drops of hydraulic fluid dripped on the floor. Worried that I had just caused a leak in the rack, I tried to move the steering wheel back and forth to get more fluid to leak, but could get any more to come out.

I'm hoping maybe I just temporarily caused a banjo connection to leak and there's no crack or anything internal going on inside the casting.
My power steering pump was having trouble circulating the fluid. It worked fine when off other then a loud noise that wouldn’t go away. But for some reason when I would shut the car off my power steering fluid would start spewing out of the reservoir.
 

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I would stick with aluminum and as for size I think the ID is the crucial dimension here. Hydraulic parts suppliers on the internet supply similar aluminum washers for far less than $80.

I ended up lightly sanding my old SMG unit washers to flatten them out and ended up re-using them. No issues so far.


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All of the washers in the VANOS system are copper washers, that system is under far higher pressures and there are a few places where there is aluminum to copper contact. Galvanic corrosion could become an issue in many places, but unclear how big of a factor it is here. Copper also has a softer birnell hardness vs alumimum, but this also depends quite a bit on the specific alloy used in the Al crush washers and whether or not the copper or Al is annealed. On my power steering rack lines, I ordered the Al crush washers, mainly due to the fact that those are a very different size than the banjo bolt size on the SMG pump, which is the same as what is used through the VANOS banjos. I have a bunch of those copper washers so, that is what I used. The critical factor in sealing is the torque of the faster joint. 25nm is the properly torque to seal the M12x1.5 banjos with the properly spec'd copper washers.
 
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