1942 - 1947 Chevrolet Shop Manual



5-1

*Section 5* HYDRAULIC BRAKES

The braking system of all 1942 passenger cars and trucks combines hydraulically operated service brakes with mechanically operated emergency brakes. Fundamentally, the braking system of the passenger cars and trucks is the same. However, due to the variance in the brake lining sizes, wheel brake drum sizes, and frame design there are several differences in the braking systems. Fig. 1 shows the brake construction.	the piston into the space between the primary cup and the check valve, keeping sufficient fluid in the lines at all times. The holes in the valve cage allow the fluid to flow through the cage and around the lip of the rubber valve cup and out into the lines during the brake application. When the brake is released the lip of the rubber valve cup seals the holes in the valve cage and the valve is forced off its seat, permitting the fluid to return to the main cylinder. The push rod assembly is held in the opposite end of the housing by means of a snap ring. The rubber boot that fits around the push rod and over the end of the housing prevents dirt or any other foreign matter from entering the main cylinder. Fig. 2.


Fig- 1—Front Brake Mechanism In order to thoroughly understand the operation of the hydraulic brake system, it is necessary to have a good knowledge of the various parts and their functions and to know what takes place throughout the system during the application and release of the brakes. MAIN CYLINDER The piston in the main cylinder, Fig. 2, receives mechanical pressure from the push rod and exerts pressure on the fluid in the lines, building up the hydraulic pressure which moves the wheel cylinder pistons. The primary cup is held against the piston by the piston return spring which also retains the return valve against its seat. The spring maintains a slight pressure in the lines and in the wheel cylinders to prevent the possible entrance of air into the system. The secondary cup, which is secured to the opposite end of the piston, prevents the leakage of fluid into the rubber boot. The holes in the piston head are for the purpose of allowing the fluid to flow from the annular space around
	Fig. 2—Main Cylinder Cross Section
	1 Inlet 2 Filler Plug 3 Reservoir 4 Housing Cover 5 Compensating Port 6 End Plug 7 Push Rod	8 Piston Cup—Secondary 9 Piston 10 Piston Cup—Primary 11 Spring 12 Valve 13 Valve Seat 14 Outlet
	WHEEL CYLINDER The wheel cylinder, Fig. 1, is a double piston cylinder, the purpose of the two pistons being to distribute the pressure evenly to each of the two brake shoes. The rubber piston cups maintain pressure on the pistons and prevent the leakage of fluid past the pistons. The adjusting covers serve two purposes: first, to cover the ends of the cylinder and prevent the entrance of dirt and foreign matter into the cylinder, and second, serve as a means of adjusting the brake shoes to the proper drum clearance, being threaded to receive the slotted adjusting screws which fit the webs of the brake shoes.