mgs
[Top] [All Lists]

Re: Brake Fluid Replacement- MityVac woes

To: Bill Eastman <william.eastman@medtronic.com>
Subject: Re: Brake Fluid Replacement- MityVac woes
From: Art Pfenninger <ch155@FreeNet.Buffalo.EDU>
Date: Mon, 20 Oct 1997 16:48:25 -0400 (EDT)
        I've tried the Mityvac on the MGA and MGB no luck with either of
them. I agree it is more work than the old pump the pedal routine.
...Art

On Mon, 20 Oct 1997, Bill Eastman wrote:

> I spent yesterday doing the annual fall maintanance on the MGA. This
> included changing the transmission fluid since I was worried that the high
> pressure additives in the Amzoil could corrode the synchro rings over the
> winter.  For giggles I decided to try Mobil 1 15W50 in the transmission.  I
> will report on how it works.  Anyone else used this?
> 
> I also replaced the brake/clutch fluid.  To do this I got out the trusty
> MityVac and vacuumed out the master cylinder.  I then filled the mc with
> fresh Castrol LMA and proceeded to use the MityVac to suck fluid out of
> each slave cylinder until they ran clear.  I have done this procedure in
> the past on my modern machinery and it has been very successful.  The first
> thing that I noticed was that a lot of suction was required to get any
> fluid out.  I was also getting an air leak around the bleeders.  Using a
> tip from this list, I got out the Teflon pipe tape and sealed the bleeder
> into the cylinder.  I also checked to make sure that the bleeder was clear.
>  It still took a lot of vaccuum to move the fluid but I wasn't getting as
> much air around the bleeder so I kept going, adding fluid to the mc as
> required.  After doing the clutch, the two back, and the left front, I went
> to pum up the brakes to return the front disk to position in case the
> suction pulled the pistons back.  The pedal sand to the floor then pumped
> up in a couple more strokes.  Air in the system.  I had never let the MC
> get low so it must have come from somewhere.
> 
> After some quality contemplation time (luckily, the radio station was doing
> a tribute to John Denver so I wasn't too distracted by the music) I figured
> that the high vacuum condition during fluid movement was causing the slave
> cylinders to suck in air when I disconnected the MityVac.  So I called the
> SO out into the garage and went on with a standard "pump and piddle" brake
> bleeding session, making sure that she released the brake pedal slowly
> after each fluid release.  After this the brakes were fine again.  I should
> have done the clutch too but I forgot.  Hopefully it will be fine.
> 
> Moral of the story?  For some reason, the MGA residing in my garage does
> not respond to MityVac bleeding.  This process works great on my daily
> driver (Ac*ra Int*gra).  I can only think that the mc design of the MG
> requires more pressure to allow new fluid into the system from the
> resevior.  On the Ac*ra, fluid starts dribbling as soon as you loosen the
> bleeder.  Perhaps this is to help retract the disk brakes?  On the MGA, you
> can remove the bleeder, clean it, and replace it without losing a drop. I
> don't know the answer but I would not recommend using MityVac for brake
> bleeding on this car anymore.  It is more trouble than it is worth.  It
> does a great job of vacuuming the old fluid out of the MC, however.
> 
> Regards,
> Bill Eastman
> 61 MGA with clean fluids
> 


<Prev in Thread] Current Thread [Next in Thread>