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Discussion Starter #1
it is not a real big deal, but being OCD I am trying to fix this: I have been observing that the power steering reservoir keeps leaking oil through its cap. Tightening the cap does not help. I noticed that there is no gasket on the cap. Looking at realoem.com I saw that there is a rubber gasket specified for it, so I concluded it is missing. I got the ring this week and tried to fit it on the cap, but came to the conclusion that this is not possible as there is no relief to put the gasket in. So, do I have a different reservoir than realoem.com shows? Do you guys have seem previous issues with this. A search on the board did not show any direct threads on this. I did notice on another board that somebody reported that there is typically no gasket on these reservoirs. What is it supposed to look like? Do you guys have gaskets?

Leak:
<a href="http://s803.photobucket.com/user/rt7085/media/M5_PS_reservoir_1.jpg.html" target="_blank"><img src="http://i803.photobucket.com/albums/yy312/rt7085/M5_PS_reservoir_1.jpg" border="0" alt=" photo M5_PS_reservoir_1.jpg"/></a>
Without the gasket:
<a href="http://s803.photobucket.com/user/rt7085/media/M5_PS_reservoir_2.jpg.html" target="_blank"><img src="http://i803.photobucket.com/albums/yy312/rt7085/M5_PS_reservoir_2.jpg" border="0" alt=" photo M5_PS_reservoir_2.jpg"/></a>
With the gasket:
<a href="http://s803.photobucket.com/user/rt7085/media/M5_PS_reservoir_3.jpg.html" target="_blank"><img src="http://i803.photobucket.com/albums/yy312/rt7085/M5_PS_reservoir_3.jpg" border="0" alt=" photo M5_PS_reservoir_3.jpg"/></a>
Realoem.com reference:
<a href="http://s803.photobucket.com/user/rt7085/media/E60_M5_power_steering_reservoir.png.html" target="_blank"><img src="http://i803.photobucket.com/albums/yy312/rt7085/E60_M5_power_steering_reservoir.png" border="0" alt=" photo E60_M5_power_steering_reservoir.png"/></a>
 

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there is a vent hole on the cap, which is stupid, and when the fluid get hot, it will come out from that hole and gets all over the place.
 

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Is the fluid at the correct level, not over filled? I'd say it's the o-ring. Every BMW I've ever had and worked on has this issue. A new o-ring fixes it every time. The o-ring sits in a groove on the underside of the cap. The old one is mashed flat so it looks like there's not a groove. Dig at it with a small screw driver or something at you'll see.
 

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Is the fluid at the correct level, not over filled? I'd say it's the o-ring. Every BMW I've ever had and worked on has this issue. A new o-ring fixes it every time. The o-ring sits in a groove on the underside of the cap. The old one is mashed flat so it looks like there's not a groove. Dig at it with a small screw driver or something at you'll see.
+1
 

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I got sick of the mess too and bought the billet one that Clyde mentioned. A little pricey. Holds twice the fluid amount and has more head space. Also a replaceable filter. I've had mine for 6 months or so and have been very happy, no leaks. Got it from Vincent at Bimmerzone.
 

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Discussion Starter #8
Is the fluid at the correct level, not over filled? I'd say it's the o-ring. Every BMW I've ever had and worked on has this issue. A new o-ring fixes it every time. The o-ring sits in a groove on the underside of the cap. The old one is mashed flat so it looks like there's not a groove. Dig at it with a small screw driver or something at you'll see.
I don't think so. Did you take a good look at those close up above? No rubber. I can guarantee you. And a round gasket does not seat on the threads or the flat (almost conical) interface surface. However, realoem shows the part.
 

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Discussion Starter #13 (Edited)
I just went out and took 2 pictures of my OEM cap. The o ring is flat but the billet reservoir doesn't leak.
Interesting. Thanks for the effort. The one I got is round. And there is clearly not good space for it as you can see in the pictures I took. There is a small ridge and I tried to get the gasket jammed in there but it would not stay (because the oil makes it slippery and the conical interface surface to the threads). I may dry off the cap, try to get the rubber seated and then screw on the cap. My gut says however that this is a no go.

Correction: Just to be sure that I am not insane I went back down. I pried hard a screwdriver in it and "pop" out came a rock hard gasket. I can't believe I missed it! The gasket just shines the same with the oil all over it, obscuring it. Just replaced it with the much more pliable new gasket. Lets see if the leak stops. Thanks for that picture. That was the key.
 

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if your reservoir leaks excessively you either need new fluid or a new reservoir. Also you should help out the power steering pump by always applying throttle when turning the steering wheel.

as B767capt pointed out the BMW part is sold w/ the filter so you have to replace the entire unit. you should be replacing the reservoir every couple of oil changes depending on how long you wait to change the fluid.

i usually change my fluid every 20,000 miles, I will try and get the AGA billet part for my fluid change.

guys note that while pentosin CHF11 is a very very VERY good synthetic fluid it does at the expense of a short lifespan; so you can expect to change it out frequently.
 

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I experience this problem on the track in hot weather. Otherwise, it never seems to occur at normal UK temps. I figured the fluid was getting hot and spilling over. I'll also try a new o-ring myself and see if it fixes the issue, thanks.
 

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Fixed mine last weekend. 5 bucks for a new o-ring from BMW and no more leaks. There's a small resis where the o-ring sits in the cap, once you get the old flattened one out the new one fits perfectly.
 

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Discussion Starter #17 (Edited)
Here is a cut through of my gasket. Clearly far away from "round". Completely packed out. I grove around with new new gasket today and no more leaks so far. Case closed.
<a href="http://s803.photobucket.com/user/rt7085/media/M5_PS_reservoir_gasket.jpg.html" target="_blank"><img src="http://i803.photobucket.com/albums/yy312/rt7085/M5_PS_reservoir_gasket.jpg" border="0" alt=" photo M5_PS_reservoir_gasket.jpg"/></a>
 

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I literally just went through this whole ordeal the other day. Glad to find out I'm not crazy. I love this forum!!!
 
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