First Generation Firebird-L Mailing List ......................................................................... You guys are both right you know. :-) There has to be the hole in the top of the MC cap to let atmospheric pressure replace the rising and falling brake fluid level otherwise there would be a vacuum (as Joe explained). The fluid is just kept separate from the atmosphere by the rubber bellows that keeps the fluid "sealed" from the atmosphere (which would contaminate it) as brake fluid absorbs moisture quickly.
Kelly http://www3.telus.net/public/68bird/ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Joe Paoletta Sent: September 19, 2009 2:41 PM To: 'First Generation Firebird-L' Subject: RE: [FGF] Brake job 101 First Generation Firebird-L Mailing List ......................................................................... Ok, I'll explain. It's simple physics. Boyles law states that pressure and volume are inversely proportional. As volume decreases, pressure increases.... Take a full, open bottle of wine and flip it over to pour it out. You'll notice that it glugs. The air is rushing in to replace the liquid leaving the container. Remember atmospheric pressure is 14.7 psi and the inside of the bottle wants to have the same pressure as the outside. Now, do the same to a 2 liter of pepsi. You'll get the same glug BUT the container will also try to collapse. As the fluid leaves the container it is creating a void that the atmosphere is trying to fill and it is easier to collapse a plastic container than a glass one. The atmosphere does not know or care that the container is there, it just wants to fill that void. The same is true of buoyancy. But, we'll save that for the next science class. Now let's apply this theory to brakes. As you apply the pedal you are forcing fluid out of the reservoir into the line etc. there has to be atmosphere to replace the lost fluid. Yes, there are those rubber bellows that collapse down BUT the kicker is there has to atmosphere above them or they are working against a vacuum. joe -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Wayne Wright Sent: Saturday, September 19, 2009 3:43 PM To: First Generation Firebird-L Subject: RE: [FGF] Brake job 101 First Generation Firebird-L Mailing List ........................................................................ . Hmm... I'm not sure I agree with that... The master cylinders I've had are sealed, with a bellows-like top to make up for the volume of any brake fluid lost. There's a hole in the top of the cap to breath, but it's on the "unsealed" side of the bellows. Wayne in OKC > >Subject: RE: [FGF] Brake job 101 >From: "Joe Paoletta" <[email protected]> >Date: Sat, 19 Sep 2009 14:37:49 -0400 > >No, you don't need to remove the cap..... the m.c. will breath. If it >were totally sealed the system would not work as it would create a >vacuum and not allow fluid to flow. > >It is covered but not 'sealed' > 6:03:00 ------------------------------------------------------------------------ Submissions to Firebird-L: <[email protected]> Unsubscribe from Firebird-L: <[email protected]> Help: <http://FirstGenFirebird.org/firebird/Firebird-L.html> Classifieds: <http://FirstGenFirebird.org/ubb/> Owner Pictures: <http://FirstGenFirebird.org/show/>
