A Plug for Calipers
When
rebuilding disc brake calipers, your shop manual or other service
instructions probably recommended removal of the pistons by using
pressure from the hydraulic system. However this method is not only
messy, but inhibits the work by allowing removal of only one piston at
a time. It also forces you to work on the caliper under the confines of
the wing while it is tethered to the chassis by the brake hose.However
there is an alternative mechanical method which permits removal of both
pistons at once while allowing you to do the work off the car. Remove
the caliper assembly from the car, disconnecting the hydraulic hose at
the caliper. Determine the inside diameter of the caliper piston, then
visit the hardware store and find a plumber's "test plug", or try the
auto store for the rubber plug used to replace the steel expansion plug
in a cylinder block core opening. Both are rubber sleeves with concave
washers at each end and a center bolt used to compress and swell the
rubber sleeve. Choose one of a diameter as close as possible to the
piston bore.
Now
cut a piece of 1/4" X 1" steel strap about 6" long and drill a hole in
the center that will fit the bolt in the expansion plug. Install the
strap on the center bolt with the nut finger tight and cut off the bolt
flush with the nut.
Insert
the plug in the piston bore, install the strap and tighten the nut
securely to cause the plug to grip the inside of the bore. If the plug
should prove too small to expand enough to grip the piston, securely
wrap a few turns of "rubber" tape around it until it is large enough to
grip as needed. Rubber tape is far better than plastic or electrical
tape because it will expand with the plug-having good friction
characteristics.
Once
the plug is tight in the bore grasp the caliper and tool assembly with
both hands, placing the thumbs on the back of the opposite cylinder and
the fingers around the strap. Squeezing the hands closed will extract
the piston from the bore. Then repeat for the opposite side. Either
this tool or a C clamp can be used to install the pistons following the
rework.
Dan Herman
Naperville, IL
Working on automobiles is inherently dangerous. Moss Motors, Ltd. is not liable for injury or damage due to incorrect installation or use of their products. All products are sold with the understanding that the safe and proper installation and use of the products is the customer’s responsibility. Follow factory workshop manual procedures and instructions, but use current shop safety standards and common sense. Some tasks will require professional advice or services which Moss Motors cannot provide.If you have a specific comment or question and you'd like an immediate reply from Moss Tech Services, don't post here - please first email: BritishTechnicalSupport@mossmotors.com Please include the Title and Location of this tip if applicable.
Forum
FAQs here.