Date: Wed, 23 Feb 2005 00:57:24 -0500
Reply-To: Jonathan Farrugia <jfarrugi@UMICH.EDU>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jonathan Farrugia <jfarrugi@UMICH.EDU>
Subject: How To: Clutch Master Cylinder
Content-Type: TEXT/PLAIN; charset=US-ASCII
How to Change a Vanagon Clutch Master Cylinder
-----------------------------------------------
Use a small 2" C-clamp to gently pinch the supply hose closed. This is
the hose that runs from the brake fluid reservoir to the top of the
clutch master cylinder. Position the clamp a few inches from where the
supply hose terminates onto the master cylinder. That keeps you from
getting so much fluid every where and negates the need to drain or siphon
brake fluid out of the reservoir. To bleed the remainder of the fluid out
of the clutch master cylinder do the following. Grab some type of
container and a section of hose to fit onto the clutch slave cylinder
bleeder valve. Crawl under the back of the van, put your hose on the
bleeder and place the end of your hose in your container. Now open the
slave bleeder valve with your 7mm wrench and let the fluid out. In order
to get all of the fluid out of the system you can head back up front and
pump the clutch pedal a few times. Now it is time to actually get into
taking the clutch master cylinder out. Before you crack any of the
connections be sure to have a bunch of towels under the master so you
don't get fluid on the carpet/paint.
Now you can crack the hydraulic line fitting that goes from the master to
the slave. As you open the fitting take care to soak up the fluid with
your rags or towels. Once the fitting is loosened and it has stopped
draining for the most part you can move on to disconnecting the supply line
from the brake fluid reservoir. The last step is to remove the two 13mm
bolts that hold the master cylinder to the aluminum bracket. As an
aid to reinstalling the master you may want to mark the location of
the 13mm bolts before you loosen them since the bolt holes are
slotted. Once those bolts are out you can slide the master down from the
pin that engages in the top of the master.
To reinstall the new clutch master cylinder I recommend putting a small
amount of grease in the top of the master cylinder where the clutch pedal
push pin operates the cylinder. After that is done then you can
reposition the master back in its place, making sure to slide the push
pin into the bore in the top of the cylinder. If I remember correctly it
is easiest to attach the hydraulic line to the slave first then after that
reinstall the two 13mm bolts and the supply line from the brake fluid
reservoir.
The best way to bleed the clutch is to crack the slave bleeder with a hose
attached and the hose in a bottle or jar. Go fill up the reservoir and
pump the pedal a bunch of times keeping the reservoir topped up. Now
check the bottle, once a fair amount of fluid has been pushed out you can
bleed the system as normal, with out worrying about a ton of air being in
the system.
Now for some theory. You will often see that people end up replacing the
slave shortly after they do the master. One possible cause for this is
not cleaning the slave or flushing it adequately. As the master failed
the failing seals allowed the aluminum piston to scrap against the bore of
the master cylinder. This generated metal particles in the system, which
accelerated wear on other parts of the system. So you need to get all
that metal out or it will prematurely wear out the parts with the weakest
link being your slave.
The best way to to this is to pull the slave while you are doing the job,
take it apart, clean and lube it and reinstall it. If you are really
anal/preventive, put some new seals in it. Before you reinstall it,
install the master and pump some fluid through the system to clean the
line out. If you don't pull and clean the slave cylinder, pump a lot of
fluid through the system. If I don't pull the slave I pump at least one
of the small bottles of brake fluid through the system as my flush. Brake
fluid is cheap relative to the parts. Then I rebleed the system in a
couple of weeks once all the parts have been moving around for a while.
This is done to help remove any metal that you might not have been able to
get out with the initial clean out bleeding.
jonathan