Brake Fluid Reservoir Question

[PKE90]

2011 E90 M3 6spd. Dealer tells me a recent clutch malfunction is due to the fact that a hose came off the brake reservoir thus starving the master slave of fluid. When looking at the reservoir from the hood towards the windshield, the black hose attached to the white tube on the top on the right side of the reservoir. I think that is an overflow tube/hose and that the fluid going to the slave is on the bottom of the reservoir. Comments please.

PS I note that the dealer also tried to tell me that the fact I put Castrol SRF brake fluid in my car contributed so needless to say I am very wary of any of their explanations.

Thanks.

[M3ANMACHINE]

This sounds very fishy to me. Interested to hear from someone with better knowledge of this.

[jimk]

This may help. Which hose are they talking about?



http://realoem.com/bmw/showparts.do?...86&hg=34&fg=15

[PKE90]

Originally Posted by jimk

This may help. Which hose are they talking about?



http://realoem.com/bmw/showparts.do?...86&hg=34&fg=15

This is helpful but now their story is becoming even more confusing. If one looks at the expansion tank in the upper right of this image there is a plastic pipe sticking out towards the right just under the seam of the top and bottom parts of the tank. That has a hose on it in my car now but I can't find that hose in these drawings - strange,no? Now I need someone to take a picture of their tank to see if they have that hose.

http://realoem.com/bmw/showparts.do?...86&hg=34&fg=15

[turbonyg]

Okay, the picture you have is a very similar tank on the 2007 335i that I have in my garage.

The hose that comes from the right side of that tank goes to hose #7 in the other picture above. That is the feed line from the brake fluid reservoir to the feed port on the clutch master cylinder.

If the hose "fell off" during operation, the clutch master cylinder (CMC) would fill with air. After a few pumps the master cylinder would be dry and full of air which would cause the clutch pedal to become soft and basically lay flat on the floor of the car.

I don't think running the CMC dry would cause it to become non-functional but it definitely makes it hard to bleed the entire system.

That help?

[PKE90]

Originally Posted by turbonyg

Okay, the picture you have is a very similar tank on the 2007 335i that I have in my garage.

The hose that comes from the right side of that tank goes to hose #7 in the other picture above. That is the feed line from the brake fluid reservoir to the feed port on the clutch master cylinder.

If the hose "fell off" during operation, the clutch master cylinder (CMC) would fill with air. After a few pumps the master cylinder would be dry and full of air which would cause the clutch pedal to become soft and basically lay flat on the floor of the car.

I don't think running the CMC dry would cause it to become non-functional but it definitely makes it hard to bleed the entire system.

That help?

That does help because it explains the symptoms...only thing that bugs me is how the hose fell off but I may just have to ascribe that to the BMW gremlins that work their mysterious ways from time to time...

[turbonyg]

The hose (#7) is basically just pushed on the tube on the reservoir and onto the CMC, I do not like this design at all. I feel that the hose could work itself loose if you have ever replaced either component. I put a hose clamp over the hoses themselves as added security.

[PKE90]

Originally Posted by turbonyg

The hose (#7) is basically just pushed on the tube on the reservoir and onto the CMC, I do not like this design at all. I feel that the hose could work itself loose if you have ever replaced either component. I put a hose clamp over the hoses themselves as added security.

Super helpful. Thanks.

[turbonyg]

No worries, glad to have helped.

[happos2]

How much fluid is needed when doing the brake fluid flush? Is it just 500ml or 1L?