Date:         Mon, 20 Jan 97 10:23:32 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         vince_pappalardo@om.cv.hp.com
Subject:      Re: Brake Cylinder Rebuilding??

Item Subject: Brake Cylinder Rebuilding??
     Jim,
     
       I have done many rebuilds and have always honed the cylinders at 
     least five or ten strokes to break any surface imperfections and 
     slightly rough up the surface to get the new seals to seat. I have not 
     ever "screwed it up with a hone" and I have had my share of the hones 
     slipping out and stones coming off.  The purpose of the honing is 
     mostly to remove surface imperfections that will cause premature 
     failure of the new seals--it does not come close to resembling a 
     boring process.  If you elect not to hone, I would highly recommend 
     running your finger over the entire surface of the bore to verify that 
     there are no imperfections.  
       As for what type of hone to use.  I have used two and three blade 
     hones.  Mostly this is dictated by the size of the cylinder you are 
     doing and the size of the hone that will fit inside it.  The three 
     stone type I feel are more stable but I don't have much a problem with 
     the two blade ones either.  Good technique is more important than the 
     hone itself.  Strive for keeping the hone shaft concentric to the bore 
     and use a in out motion that is continuos that will produce a 45 
     degree angle hone mark pattern.
       I also think you should wait on doing the rebuild on these until you 
     need them.  If you do them now you will need to store them with brake 
     fluid in them to protect the surfaces from rusting.  This is risky 
     because, unless you seal all the open ports well, the brake fluid will 
     absorb water from the air and cause the very pitting they don't have 
     now.   Moreover, the seals will start to relax and break down while 
     not in use therefore reducing there life once installed.
       I would simple clean and dry them.  Then coat the bores with a heavy 
     grease or oil that will stick to the walls to prevent rusting.
     
     Well, that's about all I can add to this discussion.
     
     
     Vince,
     '85 Westy, GL
     '90. . .some other foreign car that now seems pretty refined (but not as 
     utilitarian) compared to the Westy.
     

______________________________ Reply Separator _________________________________
Subject: Brake Cylinder Rebuilding??
Author:  Non-HP-vanagon (vanagon@lenti.med.umn.edu) at HP-Corvallis,shargw1
Date:    1/20/97 9:08 AM


Hi all,
I've recently replaced (with new) both the rear wheel cylinders on our 88 
Vanagon - one was leaking.  Also, recently I had the clutch slave cylinder 
replaced on my 87 Syncro.  
     
I'd like to rebuild the old cylinders and keep them as spares.  The bore of 
all of the cylinders is very smooth and shows no signs of pitting.  It seems 
like the leaks were like caused by old and stiff rubber seals.  The seals in 
the rebuild kits are much more flexible and the outer sealing "skirt" is a 
bit larger in diameter than the old ones.  I theorize that the seals, after 
being held inside the cylinders for 9-10 years, have assumed the diameter of 
the cylinders and no longer exert much force on the walls on the cylinder 
wall.
     
My question is about honing the cylinders.  Since they are smooth inside, 
does this realy need to be done?  I'm a bit worried about taking a cylinder 
with a nice smooth bore and screwing it up with a hone.  Also, any 
suggestions on the brand or type of hone required?
     
Thanks,
Jim Davis
87 GL Syncro
88 GL Wolfsburg