HYDRAULIC BRAKES

Evening Star, Issue 21905, 17 December 1934, Page 17

HYDRAULIC BRAKES

TIPS FOR THE OWNER-DRIVER With the increasing average speeds of the modern car it-has become essential in the interests of safety that brakes should be maintained at their highest pitch of efficiency. Although hydraulic brakes have been used for many years now they remain a mystery to many ow'ner-klriversff The following information is intended to warn such drivers of the first essentials of maintenance and to indicate reasons for defects which may develop after some years of running. CARE OF THE FLUID SYSTEM. The most important point in the maintenance programme is to keep the reservoir properly “topped up ■ this is best left to the expert at the service station, who will also eliminate any air from the oil lines and examine them for leaks. The detection of leaks, by the way, is simplified by chassis cleanliness: in ‘fact, the dismantling of mud-caked pipe unions renders the exclusion of dirt from the lines almost impossible. Unsuitable fluid should never be used on the grounds of economy. Mineral oil if purposely or accidentally introduced

into the system, may. cause serious trouble by swelling the rubber valves and cups to such an extent that they become plastic and non-resistant. If it is known that mineral oil is in the system the only effective way of removing it is to drain the lines, reservoirs, and cylinders and wash throughout in methylated spirit. U the rubber parts have not been harmed they may he refitted after washing, but all parts must be thoroughly dried before assembly, otherwise rust may form 011 metal parts. When reassembling, the pistons should be primed by dipping into brake fluid. , Prolonged use may also result in deterioration of the rubber parts, and such wear usually results in a gradual loss of efficiency. The piston of the master cylinder may need replacement after considerable mileage. When installing a new master piston or making adjustments to the plunger rod care should be ( taken to ensure correct operation of the piston. The amount of its travel must be accurately set if the piston is to uncover the recuperating hole in the cylinder; failure to do so is often the cause of brakes not releasing properly. Grabbing brakes may, of course, be caused by broken retraction springs, and this possibility should not be overlooked when one bub is affected more than the others. BRAKE SHOE ADJUSTMENT. The need of brake shoe adjustment to compensate for lining wear is usually indicated by excessive waste motion of the brake pedal. The means of adjustment, usually an external screw operating an internal' cam, controls the amount of clearance between the drum and the linings. As this clearance- is small the movement of the brake shoes on the fulcrum pins is correspondingly small and seizure at this point should be guarded against by the , , use . graphite or other suitable lubricant.