A Guide to Driveline & Braking Components

What is a Clutch Master Cylinder?

The brake master cylinder, as the name suggests, controls the brake fluid which it holds in a reservoir. It disperses this brake fluid through brake lines which are pipes and hoses connected to each wheel. It can vary the pressure in these lines based on how hard you push your brake pedal.

Clutch master and slave cylinders work as a team. Again, as the name suggests, when the clutch pedal is pushed, the clutch master cylinder increases pressure in the slave cylinder which pushes on a clutch fork, disengaging the clutch. The master has a reservoir which holds brake fluid and is connected by a line of metal pipe and hose to the slave cylinder.

What is a Drum Brake Wheel Cylinder?

Drum brake wheel cylinders are only found on drum brakes. Their role is to take the brake fluid pressure and use it to push a set of brakes’ shoes against a rotating brake drum.

Picking a Faulty Brake Clutch Master, Slave Cylinder, or Drum Brake Wheel Cylinder

The biggest issue with all these items is eventually they start leaking fluid. Because all these units are a hydraulic powered piston, the seals or bores or both gradually wear out and they need to be replaced. The leak usually starts as a small seepage and increases to a drip.

The master cylinders are located on the engine bay firewall and inspecting them is quite simple. However, you can, on the odd occasion, get them leaking into the cabin which is more difficult to spot. The clutch slave cylinder is usually under the car and involves a bit more work to thoroughly inspect it.

Wheel cylinders are located in the drum brake assembly and in most cases the wheel and brake drum need to be removed to perform a thorough inspection. They will occasionally leak onto the brake drum backing plate or you will see fluid at the bottom of the drum. By then the drum will not be braking effectively as it will be covered in fluid.

Nine times out of ten you will notice the master cylinder reservoir needs constant topping up which is a sure sign of a leak. If a braking or clutch system has sat around on a vehicle for years without being used, you may need to rebuild or replace parts of it. Because brake fluid absorbs moisture, the pipes and other brake components can rust or corrode internally.

Getting a Brake Clutch Master, Slave Cylinder, or Drum Brake Wheel Cylinder

A quick visit to your local Repco auto parts store should be able to help you out with the parts you need including brake fluid. Being consumables, replacements should be available for popular makes and models. Even if not in stock locally, they can order the part in. Just make sure the parts you need are available before pulling your vehicle apart. Less down time this way.

The range of Kelpro brake master cylinders, clutch master and slave cylinders, and drum brake wheel cylinders is a good choice. They all have a 2 year or 40,000-kilometre warranty. They are sourced from ISI 9001 and TS accredited factories and made from high quality materials that offer a long service life.

Replacing a Clutch Master or Slave Cylinder, or Drum Brake Wheel Cylinder

While replacing these parts can be challenging and may require some specialty tools, doing it yourself is doable as long as you have some experience.

Replacing a Clutch Master Cylinder

Replacing a clutch or brake master cylinder is very similar between various vehicles. They are usually connected to a clutch or brake pedal inside the cabin and bolted to the firewall inside the engine bay.

You need to disconnect the lines coming out of the cylinders and this can be the hardest job as they can be seized onto the cylinder. A penetrant can help, as well as a using a special open-end spanner (flare nut) that is reinforced to do pipework fittings.

To install the new one, simply reverse the removal process. Being the master cylinder, you will need to bleed all the lines attached to it to remove any air bubbles. This is a 2-person operation, or you can buy brake bleeding kits that turn it into a 1-person show.

Replacing a Clutch Slave Cylinder

The clutch slave cylinder may or may not be easy to access for replacement. Once you can access it replacing it is not that complex. You may need to jack up the vehicle to access it and if so, always use an axle stand. As with the master cylinder removing the line may need penetrant and a flare nut spanner and the new slave cylinder will need bleeding to remove air bubbles.

Replacing a Drum Brake Wheel Cylinder

Wheel cylinders in brake drums are easy to get to. Simply jack up the vehicle and place it on an axle stand, then remove the wheel. The brake drum can sometimes be hard to remove. Make sure the handbrake is not on and some drums have a single screw in them to hold the drum in place. Once the drum is off, check the inside of the drum and brake shoes to make sure they are free of fluid. If not, a good spray with brake cleaner and a wipe with clean, dry rags will be in order.

You need to remove the brake shoes before the wheel cylinder can be taken out. There are usually a lot of springs that need to be removed so having a manual or using your phone to document where things are, will help to put them back in the right place during reassembly. Another good tip is only do one drum brake at a time so you can use the other side as a reference when putting things back together.

Changing over the wheel cylinder can now be done. The incoming brake line may need penetrant and a flare nut tool for removal. Reinstall the brakes shoes and brake drum before attempting to bleed the wheel cylinder. If not, you will pop the pistons out of the cylinder.

As always, consult your manual for instructions and if you are inexperienced and have safety concerns about performing these tasks, have a qualified professional handle it instead. It can save you a lot of time and headaches if you preplan your job before you start.