CLEANING
A good cleaning solution removes most rust and scales. Follow manufacturer's directions in the use of cleaner. If considerable rust and scale has to removed, cooling system should be flushed. Clean radiator air passages with compressed air.
Radiator Cap
Visually inspect radiator cap, then dip cap into water and connect to tester. Pump tester to bring pressure to upper limit of cap specification. (Scheme 2) If radiator cap fails to hold pressure, replace radiator cap.
Scheme 2
With pressure tester, pressurize radiator to no more than 20 Lbs. If pressure drops, inspect for external leaks. If no leaks are apparent, remove tester and run engine until normal operating temperature is reached. Reinstall tester and observe. If after pumping tester, pressure builds up immediately, a possible leak exists from a faulty head gasket or crack in cylinder head or block.