by Joe Gorin (USA)
In the process of overhauling the hydraulic system of the brakes
of my 1980 TR7, I learned a lot that isn't in the Repair
Operations Manual, and is thus worth sharing.
My overhaul included changing to braided steel flexible hoses,
due to the recommendations made by Tim Buja, and changing to DOT5
(silicone) fluid, due to my perception of its suitability in
older, low-usage cars. But most of what I will relate below is
general information.
Materials Required
Obviously, you need the overhaul kits for the master cylinder,
both calipers and both rear wheel cylinders. These are quite
inexpensive. You will also need brake fluid, such as Castrol
LMA. I bought DOT5 (silicone) fluid because it does not absorb
moisture, and thus should not need to be bled as often (the
maintenance recommendations for fuel-injected TR7s calls for
replacing the fluid every 18 months, regardless of mileage).
DOT5 is hard to find locally; one person I talked to said it had
been removed from the market because it is not allowed in
anti-lock brakes. I found some for $11.88 per 12 oz. bottle, and
used about 30 ounces. VB and Rimmers both carry DOT5 fluid. Dan
Jones and others suggest that the moisture still gets into a
system with DOT5, but it just pools up in the lowest place.
Other materials required are:
- wheel cylinder gaskets. These look to only be available from
Rimmer Bros., although Dan Jones made his own easily.
- wheel cylinder circlips. New is much preferred to reusing the
ones that fatigue when removed.
- replacement flexible pipes. I got mine from Ted Schumaker, but
he was unable to buy fittings like the OEM hoses, so the
stainless steel braided hoses have to be held on with clamps. I
would recommend Rimmer Brothers instead; a set of three hoses is
about 35 pounds plus shipping.
- alcohol. It is recommended when changing to DOT5 to bleed
alcohol through the system first. I used less than a quart (32
ounces).
- grommets for caliper splitting. The ROM recommends not
splitting (disassembling) the calipers, but neither Dan Jones
nor I could figure out how to get the pistons both out without
splitting the calipers. When you do, it is wise to replace the
grommets (one per side). These replacements are not part of the
rebuild kit. As Mark Elbers told us, you can get replacements
from Apple Hydraulics at (800) 882-7753 (NY). Ask for Bob, or
you may have problems. Bob says some TR7s require deep grommets,
and some shallow. They will send you grommets for $2.50 each,
plus $3 S&H. The deep ones are .496" OD, .323" ID, and .110"
thick. The thinner ones are the same except they are .067"
thick. I measured my originals at .490 OD, .290 ID, .110 thick.
You can save $5 by splitting your calipers first, and only
ordering the thickness you need.
Tools required
In addition to the normal tools, you will need some unusual
tools:
- 3/8" and 1/4" dowels for "butterflies." As Dan describes it, a
butterfly is a dowel with a 1" slot cut all the way through along
the centerline. In this slot you place a piece of sandpaper, 1"
wide. You put the butterfly into a drill and use it to sand the
inside of wheel cylinders and master cylinders.
- Sandpaper. I used 280, 400 and 600 grit emery cloth in my
butterfly. One sheet of each is plenty.
- Air. Compressed air would be nice. I used a bicycle floor
pump and an assistant.
- Circle clip remover (also known as snap ring pliers). I bought
a set of four very cheap ones for $5 total at a local tool store.
I have seen this set in J. C. Whitney's catalog. You may be able
to get by without these.
- #3 size philips head screwdriver, or better yet, a #3 bit that
you can put in a torque wrench. A normal Philips head (#1 or #2)
just won't work. You will need to tighten the screws that attach
the reservoir to the master cylinder to 5 ft-lbs. I expect that
it is easy to overdo it.
Processes Required
The ROM should, of course, be your first reference for the
operations required, but I found the need for more information.
Here is what else you might need to know.
- Circlip installation (for reattaching the wheel cylinders).
Push the circlip parallel to the centerline of the stud on which
it is mounted. That is, push it perpendicular to the plane in
which it will lie when assembled. I have always pushed circlips
in the plane of their final position, but that sure didn't work
here. Push on two of the three fingers by hand, and push on the
third with a tool like an awl or a screwdriver or the nose of
some needlenose pliers.
- Use the butterfly on the M/C and wheel cylinders, using the
coarsest paper through the finest paper in order, if you see any
signs of corrosion. I saw mild corrosion on both ends of both
wheel cylinders, and the heavier corrosion on smallest bore (the
inner bore for the pressure differential sensing piston) of the
M/C.
- Master Cylinder pressure-differential-sensing piston removal.
I couldn't get mine out with bicycle-pump air, even though I
could seal up the outlets with hose clamps and inner tubes and
fingers (you'll need to leave the secondary piston in to try this
operation). I took it to a shop that tried to remove it with 150
psi air, but it didn't come out, but it did blow out my
hose-clamped inner tube seal. I found a shop (they specialize in
Italian cars) that could remove it with hydraulic pressure; they
charged me $25 for labor. Philip Johnstone reports that he makes
a hook out of 1/16" welding rods for problems like this; he bends
it and files it down to a 1/16" hook. Dan Jones reported trying
and failing to remove this part with a hook. I tried grabbing
mine with some moderate-sized electronics needlenose pliers,
filed down so they would fit in the bore, but wasn't successful.
- Drum removal. I could not get the drum off with the ROM
instructions, partly because mine are from a 5-speed TR7, thus
using the 9" drums. Here is what you are supposed to do: Look
for a hole in the silver-colored metal that you can see when you
look into the big holes in the face of the drum, if that big hole
is positioned 30 degrees forward of straight down. You'll need a
flashlight. Push that piece of metal towards the center of the
car and towards the middle of the drum with a large philips-head
screwdriver. This should release the autoadjusters so that the
drum comes off easily. Mine didn't, even though it had been off
three weeks earlier. It seems to corrode onto the hub flange.
So stick a flat-blade screwdriver into the hole in the drum such
that its wedge can separate the hub flange from the drum surface,
and pound on it with a hammer. I have been successful taking the
drums off this way without releasing the autoadjusters first;
Mike Jeffreys has been successful by only releasing the
autoadjusters; but I would recommend doing both.
- Pushing the pistons out of the calipers. As mentioned above,
split the calipers in order to push out the pistons. Then apply
high pressure air to the hydraulic port until the piston pushes
out. With a bicycle pump, I applied the pump through a rubber
washer (from an Eezibleed) which I pushed on hard enough to make
a seal. My pump has a large, flat surface on its "presta" (a
road-bicycle-popular valve) head. You can hold the extra
hydraulic ports closed with your fingers with an assistant. Put
a rag on the piston to keep it from shooting out across the room
when it finally releases.
- Don't forget that you are supposed to keep the piston with the
cylinder from which it was removed.
- The M/C kit comes with lots of pieces. Mine seemed to have a
spare o-ring, about 1" in diameter and very thin. It also comes
with a metal cap that goes on the end of the M/C that plugs into
the servo. My old one stayed stuck in the servo, so I didn't
replace it. There is also a white shoulder washer that goes into
this cap; mine fell out when I removed the M/C from the servo and
I almost didn't know it. Luckily, I dropped a wrench when
reinstalling the M/C, and found the washer on a chassis piece
when I went looking for the wrench.
- You should lubricate the joint between the two pieces of the
levers that actuate the brake shoes from the handbrake. They
sometimes corrode together and get sticky.
Summary
The task was not as big as I expected. I hope that, by telling
what I learned, it can be even easier for others. I think I
spent about 8 hours on it over an 8-day period, and I'm a very
slow mechanic. Neither my pads nor shoes needed replacing, nor
did I need to have the rotors or the drums turned. All these
operations would be completed in a complete brake rebuild.
Joe Gorin, Santa Rosa, Calif. '80 TR7, 5-sp, FI, conv.
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