1942 - 1947 Chevrolet Shop Manual



	*5-13*

	MAINTENANCE The following maintenance operations should be performed every 10,000 miles, or six months: Cleaning The power cylinder should be cleaned externally. The piston rod rubber boot should be carefully examined and replaced if torn or oil soaked. Tightening Tighten all hose clamps; check and correct all pipe fittings for looseness at the threads. Air Cleaner The air cleaner should be removed, disassembled and cleaned every six months, or 10,000 miles-more often if operating under dusty conditions. To remove and clean the air cleaner: 1. Disconnect the air intake line at the pipe fitting on the cleaner. 2. Remove the two nuts which fasten the cleaner to the power cylinder clamps and remove the cleaner. 3. Remove the snap ring and washer, hair element and screen from the housing. (Fig. 28 shows a layout of the air cleaner parts.)	the check valve. Clean and inspect the valve and reassemble. (Fig. 29 shows a layout of the Check Valve Parts.) Linkage The pedal linkage must be free and lubricated. Abnormal friction in the lever system will cause improper application or release action of the valve. Make sure the power cylinder and lever mechanism is in proper alignment, so that no bind is encountered to cause loss of power and sluggish release. Lubrication To lubricate the vacuum power cylinder and piston rod, disconnect the piston rod at the power lever. Replace the clevis pins to prevent upsetting the valve adjustment, then remove the pipe plug from the front of the cylinder. Inject 2-1/2 ounces of shock insulating fluid through the pipe plug hole. Allow enough time for the oil to be absorbed by the oil wick, then move the piston 4 or 5 strokes by hand, rotating 1/2 turn with each stroke to distribute the oil over the cylinder wall and packing leather, as shown in Fig. 30.



	Fig. 28—Air Cleaner 4. Wash all parts in clean gasoline. Allow the hair filter element to drip dry, then dip in light oil and let it drain. Clean all dirt from inside of the air cleaner housing and reassemble.	Fig. 30—Lubricating Vacuum Power Cylinder Remove the piston rod boot at the cylinder end and apply a few drops of light oil to the piston rod. Then move the rod in and out 2 or 3 times to lubricate the rod bearing and packing. Care must be exercised to prevent oil from coming in contact with the rubber boot. SERVICE Any time faulty power brake operation should occur, a test of the vacuum at the engine manifold should be made first, to make sure the vacuum at this point is sufficient to operate the brake system. With the engine running at idle speed the vacuum gauge should read between 16 to 20 inches of vacuum, depending on altitude. If maximum vacuum is being obtained a leakage test of the entire system should be made to determine the source of the trouble.

	Fig. 29—Layout of Check Valve Parts Check Valve Disconnect hose connections from the check valve, then remove the four screws and disassemble