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Discussion Starter · #1 ·
I adjusted the rear brake calipers for the emergency brakes to work properly, but during the adjustment a little bit of brake fluid came out (not uncommon as I understand). I wanted to add the amount I believe escaped during the adjustment back to the brake fluid reservoir. When I opened it, I saw 2 compartments inside it. The one on the right (see pic) has noticeably dirtier fluid in it than the one on the left. Can someone explain to me what those are? Also, if I am adding some brake fluid to it, which one should it go to?

616856
 

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The rear (right) goes to the rear brakes, and the front reservoir goes to the front brakes. It’s a good time to flush the dirty fluid out with new fluid. Bleed your brakes at each corner until clear fluid comes out, and do them in order of farthest from reservoir to closest to reservoir.
 

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Since the plunger, when you depress the brake pedal, moves forward it pushes fluid out of the rear reservoir first which goes to the FRONT brakes and if pushed further is pushes fluid out of the front reservoir which goes to the REAR brakes. Since the front brakes do most of the stopping over time the fluid becomes dirty or cloudy. As with engine oil over time brake fluid becomes contaminated and should be flushed.
 

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You do realize that if you disconnected the hoses to the calipers you need to bleed the system, right?
This particular M/C is GM-style, which has the front brakes on the front reservoir. You can also see this by following the lines out of the M/C, into the brass combo valve, and on down the frame. In any case, as soon as you bleed the brakes, the level in the reservoir connected to those wheels will go down, so it will be obvious. The actual level isn't critical; typically you want the level to be about 1/4" below the rim.
 

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Discussion Starter · #5 ·
You do realize that if you disconnected the hoses to the calipers you need to bleed the system, right?
This particular M/C is GM-style, which has the front brakes on the front reservoir. You can also see this by following the lines out of the M/C, into the brass combo valve, and on down the frame. In any case, as soon as you bleed the brakes, the level in the reservoir connected to those wheels will go down, so it will be obvious. The actual level isn't critical; typically you want the level to be about 1/4" below the rim.
I didn't disconnect the hoses to the calipers. The adjustment I am talking about did not require it.
 

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You don't need to replace the fluid you lost. From the looks of things, you have plenty. What you did was like checking the engine oil with the dipstick. You don't need to replace the oil that you wiped off the dipstick.

You should periodically flush brake fluid. It is hydrophilic meaning it likes to absorb ambient moisture. This reduces its boiling point and can cause trouble in panic stops or performance driving. Use a turkey baster to remove most of the fluid from the reservoir. Refill and bleed until you get clean fluid at all four corners.

I'm pretty bad about bleeding mine, but I do it every few years on daily drivers. On the autocross car I do it about once a year before I race. I only do about two events per year.
 

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By the way... the two reservoirs are for safety. If you blow a rear line, you won't end up pumping all the fluid out the hole. It will keep a separate reservoir of fluid so you can still have half braking until you get stopped.
 
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