Tech time again,
You all may know that I haven't had to touch any of the hydraulics on my
MGA in the 11 years since the restoration, except for flushing through
the (silicone) fluid every two years. I've had on my to-do list for a
while now to fix a little dribble from the clutch slave cylinder, and
this was the opportune moment, both engine and gearbox were out of the
car, and the slave cylinder was just hanging there in the open. I
thought I'd try a novel approach and take a few shortcuts, but I wouldn't
do anything stupid with the mechanicals.
First I left the cylinder attached to the hose in the car. I just
crawled into the engine compartment and sat on the steering rack to do
the job. I started by removing the retaining ring and the dust boot from
the slave cylinder. Then I pushed the clutch master push rod from where
I sat to force fluid to pop out the slave piston and rubber cup, pulled
out the spring, and dumped the fluid from the slave into a pan on the
floor. The aluminum cylinder bore wasn't pitted, but after 125,000 miles
it had a little wear mark in the wall from the steel piston. I chucked
up my little cylinder hone in my cordless electric hand drill and went at
the honing with the cylinder in one hand and the drill in the other hand,
using the little fluid left in the cylinder for the honing lubricant.
The bore came up smooth and clean in about five minutes, aluminum being
pretty soft and easy to hone.
Then I pushed the clutch master push rod some more to get more fluid into
the slave to rinse out the grinding dust. You know how much trouble it
can sometimes be bleeding the clutch on an MGA? That's because the
master cylinder creates a little vacuum in the line on the return stroke.
The fluid coming out of the master cylinder just gets sucked right back
in with the return of the master piston. So I couldn't get much enough
fluid into the slave to rinse it out. Well I had another novel idea to
solve that problem.
I have a hand operated vacuum pump just like the Mityvac, maybe even the
same thing sold under a different brand name. One of the pickup tips in
the set is a flat faced suction cup which coincidentally happened to just
fit snuggly into the slave cylinder bore. With this attachment I could
draw a nice vacuum inside the empty slave cylinder and draw through all
the fluid I wanted. On my first try I was amazed at how small the MGA
1500 master cylinder reservoir is, drawing air into the line when the
little plastic vacuum bottle was only half filled with fluid. I had the
bottle of fresh fluid sitting right there by the windshield, so I filled
up the M/C reservoir and tried again.
In a minute I had the slave rinsed out and ready for the stuffings. Then
came this other nifty idea. Holding the slave cylinder with the open end
up, I managed to draw enough fluid in to fill it nearly to the top. Then
I dropped in the spring and the rubber cup. By shoving the rubber cup in
edgewise first and submerging it in fluid, then turning it face on like
it belongs, I was able to get it installed with no air behind it. Then I
dumped the excess fluid out of the slave, used a paper towel to dry out
the cylinder in front of the rubber cup, dropped in the metal piston, and
installed the dust cover and retaining band. Presto !!! Instant action
clutch without having to bleed it after the overhaul.
Sometimes the world does work right.
Barney Gaylord
1958 MGA with an attitude
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