how to bleed master cylinder?

[Bernard Littau]

Hi Per,

I respectfully submit a counter opinion to yours :-)

I once upon a time bought a Master Cylinder for a Bronco II, and it came
with some plastic fittings and short plastic hoses that allowed one to feed
the output of the MC back into the reservoir.  The installation instructions
for this Bronco MC were quite clear that the MC needed to be bled before
install, where the output was fed back into the reservoir, until no more air
was in the MC -- if this was not done, the warrantee was void, or whatever.
They claimed the reason was that it was just impractical to bleed such an MC
air free once it was installed.

It took quite a lot of pumping with this recirculation setup before the MC
was truly air free -- I guess some of the air stays trapped in the MC
chambers for a long time, perhaps as sticky bubbles :-), before the flow of
fluid eventually works the air out.

Yes, when you disconnect the plastic fittings, a small amount of air gets
into the passage at the end of the MC, but that is easily bled once the
whole thing is installed.  It is to get the internal chambers air free that
the pre-install bleed is useful for.

I have since used these plastic fittings and hoses on several MCs (including
one 5ktq) to do a pre-install bleed, and I rather easily got the whole
system air free after the install was complete.

I think there is some value in a pre-install bleed.  It sure seemed to save
time and brake fluid in the end.

YMMV.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq


>
> All the info I've heard before is that it is a waste of time, and a
> complete mess to try to bleed it before you install it. Not only that,
> but there really isnt any way you install it without getting any air in
> the lines anyways.
>
> Just my $0.02
>
> PerL
> 87 Cq
>
> Ron Wainwright wrote:
>
> >  Listers,
> >
> >  I'm going to be replacing my master cylinder on my
> >87 5ksq and would like to know how I would bleed it
> >before bolting it to the car.
> > Any BTDT would be great, I've looked at Scotts web
> >site but no info on R&R.
> >Thanks
> >Ron
> >87 5ksq many mods
> >90 200tqa many mods
> >
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>