master cylinder assembly tool

Hit Counter

If you repair a master cylinder, you need to take out and re-insert a pin[s], screw stop or circlip that holds everything in place. The parts are under spring pressure.
By compressing everything inside by using this tool, it will allow you to release your hand and insert the piston holding device.
It is another pair of hands, very useful.


Position the longer hook into the push rod recess and press it in until you can locate the shorter hook into the brake pipe hole. Position the piston slots vertically when rebuilding. Let go of the tool, insert pin etc.
The pin  [called a roll pin] has a slot in it, the slot must face towards the outside  where the tool is held to the piston.        Simple!!!!!

There seems to be 4 types or variations of the master cylinders. You can use this tool on any of them. Everything inside a cylinder is spring loaded and the pistons are held and secured in place by several methods, depending on the type of cylinder. It can be a circlip, a roll pin [the type with a long slot over its length] or a screw plug with a hole in its top to allow brake fluid to drain into the cylinder from the reservoir. The screw plug has a screwdriver slot in its top to be able to use a flat bladed screwdriver to take it out or to put it back in. You must utilise the tool before taking any securing device out, to prevent parts flying out and being lost. When re-building a cylinder, always compress the parts with the tool before fitting a securing item. You can see what is securing the piston, once you have drained the reservoir and taken it off. The 425 model uses a circlip to secure the piston and internals. The later type dual master cylinder has 2 pistons and 2 roll pins to secure them.

The tool locates where the push rod actuates the piston and also fits into the top brake pipe threaded hole. Use the long end and push the tool inwards to compress the parts and then insert the smaller end into the hole. All the parts are now held in place with the pin[s] free from the stops. Remove circlip, pin[s] or screw and carefully dismount the tool. Cleanliness is very important when attempting this repair. The correct brake fluid must also be used. If in doubt, always ask. Advice is free.

Piston securing methods by year and type......

2cv425/35 inception to finish of production.....circlip.....single piston.

Ami models....> September 69... cylinder with central recirculation valve...roll pin...single piston.
Ami models...September 69 > October 71....screw plug...single piston.

2cv and Dyane models > 76...cylinder with central recirculating valve...roll pin...single piston.
Dyane models...>July 77... roll pin...single piston [no recirc valve]

2cv and Dyane models 76 >....
Ami models... October 71 > October 76
Ami models...October 76 > September 78
2 roll pins securing 2 pistons. Dual type.