Rear Brake Caliper Rebuild-Restoration.
Posted: Sun Jun 19, 2011 10:23 am
Image # 1.
The rear brake caliper looks pretty sad after more than twenty years
of service, they should be serviced at more regular intervals, but like
many things automotive... if it ain?t broke ...don't fix it.
So we want to go from a very grungy looking old caliper...
Image # 2:
To this... a completely rebuilt & restored near perfect
rear brake caliper.
Image # 3:
The dismantling can reveal many things, you live in hope that the
internal piston cylinder bore of the caliper has not been wrecked
by corrosion, before a close inspection was made, this bore
looked like it was not in very good condition.
But after a degrease and hot wash blast and then a quick dry
with compressed air it looked OK.
The pistons were sods to remove, but after a soak with WD 40
and a large amount of air pressure from the workshop compressor
they finally moved upwards and were popped out (Careful here,
they can come out like missiles? cover with a large rag.
The next step was to take
all the calliper components to a mate?s workshop to bead blast
to strip every bit of paint and rust back to bare metal.
This sure beats most forms of metal cleaning, but the parts must be
cleaned afterwards with compressed air, the outside of caliper housings
must be painted within an hour or so to prevent oxidation
on the cast iron occurring. The special paint used on the calipers
was 3M-brake caliper paint (Spray can)... about 4 to 5 coats
were applied along with a hot air quick drying process
(Hair dryer) was used between coats.
The hand brake mechanism on both calipers was checked &
rebuilt with new pins etc to get rid of the wear that occurs over a long period
of service, the parts were then sent to the electroplaters to be gold
zinc passivated for protection.
Image # 4:
The scourge of brake calipers, old hard chromed pistons that
succumb to moisture and corrosion, there's only one place for
pistons in this bad state, and that is the rubbish bin.
We bought some free machining stainless bar and machined up
a set of four new stainless steel pistons, what a difference
they make.
Image # 5:
You might think that painting the calipers is a tricky job?
Well it could be if you are not careful, the biggest worry
is preventing any paint getting into the piston bore.
We solved that problem by machining up a wooden plug
that simply slipped into the bore recess, a long wood
screw was then inserted to make insertion and removal
a simple job; note the shape of the plug.
We wanted to get some paint into the first groove where the
rubber dust/moisture cover seal rim is inserted, but a very
small amount of colour mist did find it's way into the bore,
but was easily removed with a cotton swab saturated with
paint thinners.
The mating faces of each caliper was masked off with
tape and trimmed with a sharp knife.
Image # 6:
The Lotus workshop manual says "On no account should
you dismantle the caliper halves" Why not?
They make it sound like re-assembly is some deep dark secret known
only to a few select people.... are they afraid that the calipers
will be mixed with another and end up being a badly matched
pair... difficult to do if you only have two calipers to work with!
Or maybe they think that someone will assemble the two halves
minus the small O-ring that provides the seal between the transfer
gallery from one caliper to the other.... but you'd have to be a complete
idiot to do that. And yes, it is important to understand what you are
about if you delve into brake calipers, the workshop manual
also does not provide any torque figures for the 3/8" and 5/16" UNF bolts
that hold the callipers together.... but 33-38 foot-pounds is about right
for the 3/8? & 14 -19 foot pounds for the smaller bolts... too easy.
Another great advantage of splitting the calipers is that it makes
the rebuilding job very easy, it is such a simple job to insert the piston
seals, and quite simple to place the dust cover lip correctly into the
groove before carefully the pistons are inserted, I've tried this
with the calipers assembled and it drives you nuts trying to
get the seal, dust cover & piston in.
Image # 7:
Now before you embark on the caliper rebuilt project spend
A couple of hours building a brake caliper bench vice holding
Tool, this will make the job a whole lot more enjoyable.
The tool is designed to rotate 360Deg on the base, so
Whatever it is you have to access, the tool will allow that.
Image # 8:
The caliper jig or holding tool, simple in design and simple
To make, well worth the effort to have this tool in your workshop,
sure, you are not going top use it much, but I have a whole bunch
of tools that make servicing and working on the elan so much easier.
So there you have it, the hand brake rods will be attached at later date,
as will the drive shafts, but that will down the road a bit yet.
Image # 9:
There are only two ways to remove caliper pistons that are
seized in the bores, you may need to use a penetrating compound,
Don?t worry, this can be removed later during restoration.
Now, the first and best way I believe is to force them out
with air pressure,as you can?t lever them out. Take a look at
Image # 9. This is small bung machined from urethane, yes the
same stuff that suspension bushes are made from, it has
a small hole drilled through the bung, note also the small
spigot on one side of the bung?refer to image seven
and you will notice the O ring recess or port, place the
spigot of the bung into the recess, holding the bung in one hand,
take the air compressor airline nozzle in the other, place the
nozzle into the hole in the bung, and pull the trigger on the air
nozzle and hold it tight, also place a heavy rag over the
caliper piston, as when the piston ejects, it will come out
with considerable force.
This method will 95% of the time, remove stubborn pistons,
Depending how badly seized they are, and if they are totally
seized, then new calipers may be required.
Have fun, and work carefully.
CeeJay
The rear brake caliper looks pretty sad after more than twenty years
of service, they should be serviced at more regular intervals, but like
many things automotive... if it ain?t broke ...don't fix it.
So we want to go from a very grungy looking old caliper...
Image # 2:
To this... a completely rebuilt & restored near perfect
rear brake caliper.
Image # 3:
The dismantling can reveal many things, you live in hope that the
internal piston cylinder bore of the caliper has not been wrecked
by corrosion, before a close inspection was made, this bore
looked like it was not in very good condition.
But after a degrease and hot wash blast and then a quick dry
with compressed air it looked OK.
The pistons were sods to remove, but after a soak with WD 40
and a large amount of air pressure from the workshop compressor
they finally moved upwards and were popped out (Careful here,
they can come out like missiles? cover with a large rag.
The next step was to take
all the calliper components to a mate?s workshop to bead blast
to strip every bit of paint and rust back to bare metal.
This sure beats most forms of metal cleaning, but the parts must be
cleaned afterwards with compressed air, the outside of caliper housings
must be painted within an hour or so to prevent oxidation
on the cast iron occurring. The special paint used on the calipers
was 3M-brake caliper paint (Spray can)... about 4 to 5 coats
were applied along with a hot air quick drying process
(Hair dryer) was used between coats.
The hand brake mechanism on both calipers was checked &
rebuilt with new pins etc to get rid of the wear that occurs over a long period
of service, the parts were then sent to the electroplaters to be gold
zinc passivated for protection.
Image # 4:
The scourge of brake calipers, old hard chromed pistons that
succumb to moisture and corrosion, there's only one place for
pistons in this bad state, and that is the rubbish bin.
We bought some free machining stainless bar and machined up
a set of four new stainless steel pistons, what a difference
they make.
Image # 5:
You might think that painting the calipers is a tricky job?
Well it could be if you are not careful, the biggest worry
is preventing any paint getting into the piston bore.
We solved that problem by machining up a wooden plug
that simply slipped into the bore recess, a long wood
screw was then inserted to make insertion and removal
a simple job; note the shape of the plug.
We wanted to get some paint into the first groove where the
rubber dust/moisture cover seal rim is inserted, but a very
small amount of colour mist did find it's way into the bore,
but was easily removed with a cotton swab saturated with
paint thinners.
The mating faces of each caliper was masked off with
tape and trimmed with a sharp knife.
Image # 6:
The Lotus workshop manual says "On no account should
you dismantle the caliper halves" Why not?
They make it sound like re-assembly is some deep dark secret known
only to a few select people.... are they afraid that the calipers
will be mixed with another and end up being a badly matched
pair... difficult to do if you only have two calipers to work with!
Or maybe they think that someone will assemble the two halves
minus the small O-ring that provides the seal between the transfer
gallery from one caliper to the other.... but you'd have to be a complete
idiot to do that. And yes, it is important to understand what you are
about if you delve into brake calipers, the workshop manual
also does not provide any torque figures for the 3/8" and 5/16" UNF bolts
that hold the callipers together.... but 33-38 foot-pounds is about right
for the 3/8? & 14 -19 foot pounds for the smaller bolts... too easy.
Another great advantage of splitting the calipers is that it makes
the rebuilding job very easy, it is such a simple job to insert the piston
seals, and quite simple to place the dust cover lip correctly into the
groove before carefully the pistons are inserted, I've tried this
with the calipers assembled and it drives you nuts trying to
get the seal, dust cover & piston in.
Image # 7:
Now before you embark on the caliper rebuilt project spend
A couple of hours building a brake caliper bench vice holding
Tool, this will make the job a whole lot more enjoyable.
The tool is designed to rotate 360Deg on the base, so
Whatever it is you have to access, the tool will allow that.
Image # 8:
The caliper jig or holding tool, simple in design and simple
To make, well worth the effort to have this tool in your workshop,
sure, you are not going top use it much, but I have a whole bunch
of tools that make servicing and working on the elan so much easier.
So there you have it, the hand brake rods will be attached at later date,
as will the drive shafts, but that will down the road a bit yet.
Image # 9:
There are only two ways to remove caliper pistons that are
seized in the bores, you may need to use a penetrating compound,
Don?t worry, this can be removed later during restoration.
Now, the first and best way I believe is to force them out
with air pressure,as you can?t lever them out. Take a look at
Image # 9. This is small bung machined from urethane, yes the
same stuff that suspension bushes are made from, it has
a small hole drilled through the bung, note also the small
spigot on one side of the bung?refer to image seven
and you will notice the O ring recess or port, place the
spigot of the bung into the recess, holding the bung in one hand,
take the air compressor airline nozzle in the other, place the
nozzle into the hole in the bung, and pull the trigger on the air
nozzle and hold it tight, also place a heavy rag over the
caliper piston, as when the piston ejects, it will come out
with considerable force.
This method will 95% of the time, remove stubborn pistons,
Depending how badly seized they are, and if they are totally
seized, then new calipers may be required.
Have fun, and work carefully.
CeeJay