Brake fluid reservoir

[Colin1337]

While installing my coilovers, I noticed my brake fluid reservoir is bone dry. Any one else have this problem, or know what could cause this? None of my other cars have ever done this, but then again I've never owned a new car before...

 

[rodmoe]

The upper res or the main res ?
Notice the main res (1) is shared with the Clutch (3) also and the upper res (2) is for ease of filling..

 

[MOFiST]

I love these 3d drawings. Where did you come by this?

 

[rodmoe]

Shop manual via HelmInc dot com

 

[Colin1337]

It's the upper res.
I looked after driving it earlier and it was back to just about 1/4 the way full. Odd

 

[NorthernProducer]

It's the upper res.
I looked after driving it earlier and it was back to just about 1/4 the way full. Odd

Here's my educated guess...when setting overnight, the brakes cool causing the rotors to contract enough for the pads to "relax" back to the cooled rotors. This takes volume out of the system...probably enough to look like a lot at the top res. Then after a drive (and several brake actuations) the brakes warm up causing the rotors to expand again...thus moving the pads back into the calipers enough to replace the fluid in the top res. Shared res systems like used on the ST will cause a more dramatic change in levels like you evidenced. I'm guessing the level in the top res is showing close to the full mark when you returned from an extended drive?

 

[xplorguy]

I show no fluid in the upper (visible) reservoir...it has been this way since new. I too am assuming this is to spec. I have never checked it directly following use but will try to remember to do this and see if any fluid is visible.........