Bubble in the Front Brake Reservoir 2019 GSA

passedetp · Mar 15, 2020

I've read most of the posts concerning the front brake issues on the 2019+ models. I have yet to see any fluid leaks out of my front brakes, but the other day I noticed a bubble in the front reservoir. It sits right at the top of the sight ring.

I am thinking about opening the top of the reservoir and letting it escape overnight. However, I want to make sure that this isn't a sign of a larger problem. I couldn't find any other posts in the recent brake threads that mentioned this as a symptom of the larger issues some folks have been dealing with.

Additionally, will leaving the reservoir open help or will I need to bleed the brakes? I have a GS911 to do the brake bleed and I am pretty sure they need to be bled after the bike's first year on the road - I could be wrong.

Looking for any help from anyone who may have found a bubble, too.

Take care,
Austin

pglaves · Mar 15, 2020

passedetp said:
I've read most of the posts concerning the front brake issues on the 2019+ models. I have yet to see any fluid leaks out of my front brakes, but the other day I noticed a bubble in the front reservoir. It sits right at the top of the sight ring.

I am thinking about opening the top of the reservoir and letting it escape overnight. However, I want to make sure that this isn't a sign of a larger problem. I couldn't find any other posts in the recent brake threads that mentioned this as a symptom of the larger issues some folks have been dealing with.

Additionally, will leaving the reservoir open help or will I need to bleed the brakes? I have a GS911 to do the brake bleed and I am pretty sure they need to be bled after the bike's first year on the road - I could be wrong.

Looking for any help from anyone who may have found a bubble, too.

Take care,
Austin

The fluid level ought not be as high as the top of the circle if the reservoir is as level as possible. The reservoir might be overfilled. Protect any paint beneath the reservoir. Remove the top. Use a syringe to remove some fluid so that you can clearly see the top of the fluid (with air above it) in the sight window when the reservoir is as level as possible turning the bars.

akbeemer · Mar 15, 2020

I think what you are seeing is the upper edge of the fluid in the reservoir (meniscus). Seeing this is normal since the purpose of the sight glass is to allow you to check the level. There is always air in the reservoir above the fluid. I agree that it can look like a bubble.

Omega Man · Mar 15, 2020

Can you post a picture of this “bubble”? I’m not familiar with brake fluid supporting a bubble. If you have some brake fluid around, shake it up and watch for similarities.
OM

stooie · Mar 15, 2020

passedetp said:
I've read most of the posts concerning the front brake issues on the 2019+ models. I have yet to see any fluid leaks out of my front brakes, but the other day I noticed a bubble in the front reservoir. It sits right at the top of the sight ring.

I am thinking about opening the top of the reservoir and letting it escape overnight. However, I want to make sure that this isn't a sign of a larger problem. I couldn't find any other posts in the recent brake threads that mentioned this as a symptom of the larger issues some folks have been dealing with.

Additionally, will leaving the reservoir open help or will I need to bleed the brakes? I have a GS911 to do the brake bleed and I am pretty sure they need to be bled after the bike's first year on the road - I could be wrong.

Looking for any help from anyone who may have found a bubble, too.

Take care,
Austin

Austin:

First of all, congratulations on your new scoot! Here's wishing you many happy miles on it.

1. Don't leave the lid off of the reservoir for any significant length of time - only bad things will happen. The fluid absorbs water from the atmosphere; leaving the cover off will greatly accelerate this. Dust from the air can settle in the fluid. This, as you might imagine, is also bad. The brake master cylinders have tight tolerances between the piston and bore. Dust in there can act as an abrasive and cause performance-degrading wear.

2. The brake service required after the first year is not to bleed the system, it's to flush the system and replace the old fluid with new.

Ride long and prosper!

easy · Mar 15, 2020

akbeemer said:
I think what you are seeing is the upper edge of the fluid in the reservoir (meniscus). Seeing this is normal since the purpose of the sight glass is to allow you to check the level. There is always air in the reservoir above the fluid. I agree that it can look like a bubble.

+1

Unless it is affecting your braking (and you did not say it is), I would leave it alone. Unless you have a good deal of brake related mechanical experience, you could easily create a problem where none exists. If you are really concerned, take it to the dealer and have them look at it. It is very much under warranty.

E.

ccolwell · Mar 16, 2020

Ditto to all of the above. DOT 3/4/5.1 doesn't have the surface tension to maintain a bubble. When air does bubble up when one bleeds or changes fluid, the bubble pops and vanishes. And it is the best paint remover out there. Feel free to ask me how I know. And if you haven't changed brake fluid before, cover everything with wet towels and have a bucket of water or a hose near by. Lastly, after changing brake fluid for the last 3 decades + I learned a new trick this year. Poke a large hole on one side of the foil covering the top of the bottle and a small air hole on the other. It makes filling the reservoir a much less fraught process than removing the foil entirely, which I always did before.

stooie · Mar 16, 2020

ccolwell said:
Poke a large hole on one side of the foil covering the top of the bottle and a small air hole on the other. It makes filling the reservoir a much less fraught process than removing the foil entirely, which I always did before.

BRILLIANT!! Thanks for sharing!

pglaves · Mar 16, 2020

stooie said:
BRILLIANT!! Thanks for sharing!

+1

lee · Mar 16, 2020

PGlaves said:
The fluid level ought not be as high as the top of the circle if the reservoir is as level as possible. The reservoir might be overfilled. Protect any paint beneath the reservoir. Remove the top. Use a syringe to remove some fluid so that you can clearly see the top of the fluid (with air above it) in the sight window when the reservoir is as level as possible turning the bars.

In the R1200RS BMW Repair Manual it shows to fill the reservoir to the top of the circle.
Top of the circle, not top of the window.

lee · Mar 16, 2020

akbeemer said:
I think what you are seeing is the upper edge of the fluid in the reservoir (meniscus). Seeing this is normal since the purpose of the sight glass is to allow you to check the level. There is always air in the reservoir above the fluid. I agree that it can look like a bubble.

I agree.

passedetp · Mar 16, 2020

Omega Man said:
Can you post a picture of this “bubble”? I’m not familiar with brake fluid supporting a bubble. If you have some brake fluid around, shake it up and watch for similarities.
OM

As requested, this was just after a 2 hour ride today with no sponginess or other issues from the front brake.

passedetp · Mar 16, 2020

akbeemer said:
I think what you are seeing is the upper edge of the fluid in the reservoir (meniscus). Seeing this is normal since the purpose of the sight glass is to allow you to check the level. There is always air in the reservoir above the fluid. I agree that it can look like a bubble.

I appreciate your response.

I posted a photo in another reply and I have my doubts that what I am seeing is the meniscus. It seems too large.

Let me know what you think when you see the pic. I could be wrong.

Take care,
Austin

ccolwell · Mar 17, 2020

passedetp said:
As requested, this was just after a 2 hour ride today with no sponginess or other issues from the front brake.

View attachment 77549

That's normal. IMO, you don't want to fill the reservoir so much that you cannot see some air above the fluid. 1) it assures you, ok, me, that there is fluid in there; 2) let's me monitor any change in fluid level.

ccolwell · Mar 17, 2020

stooie said:
BRILLIANT!! Thanks for sharing!

That came from one of the last issues of MCN. Good to see as I thought the tech answers section had deteriorated in the last couple of years.

akbeemer · Mar 17, 2020

passedetp said:
As requested, this was just after a 2 hour ride today with no sponginess or other issues from the front brake.

View attachment 77549

Looks okay to me.

lee · Mar 17, 2020

passedetp said:
As requested, this was just after a 2 hour ride today with no sponginess or other issues from the front brake.

]

Both of our bikes look like that.
It was hard to get a good picture.

lkraus · Mar 17, 2020

Not a bubble, it just looks like one because of distortion caused by the inside shape of the view port, which is not a flat surface, and light refracting through the plastic. As long as the fluid is above the lower horizontal line, you are good.

Omega Man · Mar 17, 2020

passedetp said:
As requested, this was just after a 2 hour ride today with no sponginess or other issues from the front brake.

View attachment 77549

Had to look at mine.....fluid settles right out.

lkraus said:
Not a bubble, it just looks like one because of distortion caused by the inside shape of the view port, which is not a flat surface, and light refracting through the plastic. As long as the fluid is above the lower horizontal line, you are good.

Looks ok (and similar) to me.

OM

passedetp · Mar 18, 2020

ccolwell said:
That's normal. IMO, you don't want to fill the reservoir so much that you cannot see some air above the fluid. 1) it assures you, ok, me, that there is fluid in there; 2) let's me monitor any change in fluid level.

Awesome.

Thank you for the time. I was getting mentally prepped (excited) to flush some brakes, but will use that time to just go ride.

Take care,
Austin

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