Date: Wed, 9 Nov 2011 21:10:45 -0800
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Bleeding brakes - 1.9 - questions
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thanks for posting this article.
right off the bat though ..
the author does not really mean 'brake fade' when he lists symptoms at the
top.
he means poor braking action ..
for actual brake fade ......which occurs when the brakes get too hot ..
one would not replace a master cylinder to fix that ,.......true 'brake
fade.'
A poor master brake cylinder can not cause 'brake fad' .
going downhill and braking too much causes actual 'brake fad.'
I won't bore people with a critique of the whole thing..
hopefully..........and ....
in step six it's 13mm hex nuts holding the MC to the booster.
he says to tighten the new MC down to the booster first..
I say ......install the nuts and tighten them down mostly ..but leave the MC
a bit loose..
this helps with getting the brake lines started nicely in the MC .
After those are in without being cross-theaded , then fully tigten MC nuts.
also ...
he does not mention 'bench bleeding' .
On *any* new master cylinder ..bleeding goes infenitely better if you
'bench bleed' it first..
that's so it has fluid in it, and 'then' it can pump fluid out to the
wheels.
Vanagons happen to be the only vehicle anywhere that one person can bench
bleed the MC in place, on the van, by themselves. Very handy ..
*another* reason why Vanagons are so great !!
(super easy to work on in about 90 to 95 % of the vehicle )
usually bench bleeding is done on the work bench with MC in a vice..
but it can be done in situ in a vanaogn.
the way I do it ..starting with both lines lightly tightened down ..
fill resevoir ( not 'tank' ) with BF ..
open one line, push pedal to floor ..and while holding pedal down, tighten
that line.
Do the first one twice or 3 times,
then do the other one, same deal...a few times.
do them both back and forth until each is letting out air-free BF when you
push the pedal to the floor with line crakced open.
the first time you push the pedal to the floor ., with line nut cracked
open, you can't see the air coming out ..
by the 2nd or 3rd time you'll see BF with air, or just BF.
when it's at least somewhat bench bled, then bleed to the wheels in the
normal manner.
I just start at the LF ....and then LR, then RR, then RF ..
and I often do the LF one again.
then test pedal for firmess and height. It should be right up there.
Naturally ....make sure you bleed each wheel enough.
I usually do the clutch slave at the same time..
just remember to push on the clutch pedal and not the brake pedal for that
one.
( if your slave or clutch MC are old or shakey ....might be better to leave
them alone and not start a whole new issue ) .
there are two manual methods..
the 'buddy' method ..the ole ..........pedal down with bleed valve open,
then close valve, then let pedal up ...
and repeat.
That is not the best method really.
Much better is the bottle of brake fluid with a clear hose in it method
..( hose all the way to the bottom of the jar or bottle ..the end of the
clear hose has to stay below the BF level in the jar. I rig mine with a
weight ...and a tight fitting in the bottle top ..so the hose stays down
there like you wnt. )
this method you can do by yourself..
and the big advantage is ..
you get to watch old darker BF move through the clear tube and be replaced
by clear new BF ..
and you get to watch for air bubbles..
and for them to be there at first, and then to stop.
about correded threads on bleed valves..
especially in the rear, start shooting them with penetrating oil as soon as
you even start thinking about replacing the MC. You sure don't want them
breaking off.
Good german rear wheel cylinders have 7mm hex bleed valves. If you find
1/4 inch ..those are on cheaper rear wheel cylinders sometimes.
If one mus replace 'just' a rear wheel cylinder ..it can be done without
taking the brake shoes off ..
you can 'sneak' a new wheel cylinder in there. ( I almos always take the
wheel mounting flange off to work on the rear brakes ...it's very nice with
that thing out of the way. )
on front calipers with two bleed screws..
just bleeding the upper one is fine. Air rises after all.
Happy successful break bleeding !
scott
www.turbovans.com
oh yes...I put the tinest dab of grease on the tip of the rod coming out of
the brake booster..
I don't want bare metal-to-metal contact where the rod pushes on the
cylinder in the MC.
----- Original Message -----
From: "Robert Stevens" <mtbiker62@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, November 09, 2011 8:12 PM
Subject: Re: Bleeding brakes - 1.9 - questions
Bentley may describe a test, or likely another of "us" here will proffer a
suggested method.
This is a good description of the process of replacing the MC.
http://www.vanagonauts.com/Brake-master-cyclinder190.htm
Bentley 30.2
bob
On Nov 9, 2011, at 8:18 PM, Jeff Lincoln wrote:
> Makes sense Bob - is there a way to test the MC? It's easy enough to swap
> out but would like to check it if there is a way to do so.
>
>
> --
> Thanks,
>
> Jeff
> '85 GL (Gertie)
> '90 Carat (Grover - the noble parts donor)
> '78 Bus (Melissa) Patty's Bus
