The test pressures for the front brakes are 100 kg/cm². These pressures are given for a cold state of the brake system. The temperature of the drums and discs during emergency braking from a speed of 90 km/h reaches 80°C, and during a long descent on the brakes it can reach 400°C. The pressure should be increased even more as the temperature of the brake fluid in the cylinder increases.
Normal pressure in a hydraulic system when the brakes are not applied is negligible. When the brakes are applied, the pressure increases rapidly and remains in the system until the pedal is released. Every driver can imagine how quickly the pressure increases by equating the rate of its rise with the speed of his own reaction during emergency braking.
Recent studies have shown that corrosion of brake lines can lead to brake failure after just 80 days of exposure to salt used to melt ice and snow on roads. This effectively makes it automatic to suspect that brake lines on a four-year-old car are defective. Copper alloy lines can be used as replacements.
All of the above points to the need for regular inspection of the tubes. Obviously, inspection should be carried out in the fall before winter and in the spring - to assess the extent of damage caused by corrosion.
Trace the routes of all hard tubes and wash or brush off any dirt. If the tubes appear to be coated with any underbody anti-corrosion compound, do not touch them. Inspect the tubes for dents that may have been caused by flying rocks. If you find any, replace the affected section of tube, but read the rest of this section before doing so. Any exposed section that shows signs of corrosion or pitting on the outside may need to be replaced.
The flexible hoses that run to each front wheel from underneath the vehicle to each rear wheel should not be worn or cracked. Bend them and see if any cracks appear on the surface. If the hoses are stiff and inflexible or twisted, they are nearing the end of their service life. If in doubt, replace the hoses. Also make sure that they do not rub against the body.
Before attempting to remove the tube for replacement, it is important to be sure that you have the necessary replacement parts if you do not want to be without your car for a long time. Tubes are often damaged when removed.
Where the rigid tubes connect to the flexible hoses, support brackets are installed and the flexible tube is held in place by a U-shaped clamp that fits into a groove in the nipple. Before using a wrench, soak the nipples in brake fluid as there is always a small amount of corrosion in the nipple that will prevent loosening. While the nipples are soaking, place a piece of plastic wrap under the brake fluid reservoir cap and screw the cap back on. This is to minimize fluid leakage from the disconnected tubes. Hold the Allen key on the flexible hose coupling while loosening the nipple on the rigid tube. Then pull the clamp out to release both tubes from the bracket. To remove the flexible hose, you will need to do this on both ends. The rigid tube on the other end will only require loosening the nipple from the barrel or connector. When replacing a flexible hose, be careful not to damage the nipples of the tubes that attach to it. If the nipple is particularly stubborn, be prepared to replace the rigid tube as well. This happens quite often when using open-end wrenches. It may be worth spending a little money on a special nipple wrench, which is like a box wrench with a notch for the tube to pass through.
If you order a new tube from a workshop, take the old one with you as a sample so that the nipples and sockets at the ends are identical.
Replacing hoses or tubes is done in reverse order. Care must be taken to ensure that the fittings are aligned when tightening, so as not to damage the threads. This means that it may be necessary to bend the tube slightly where it enters the connection, but this bend should never be too sharp.
When installing flexible hoses, be careful not to twist them. This can happen when the fittings are finally tightened if the end of the flexible hose is not held with a wrench.
If a rigid tube is removed or a fitting is loosened to the point that air can enter the system, the system should be bled.
(The original can be found on the website: MitsubishiMan.ru)