Booster valves


  • Remove induction piping from booster heads.
  • Pressurize discharge manifold to 551 – 689 kPa (80 – 100 psig)
  • By looking into intake part of booster heads, the intake portion of the valve can be seen. Using a screwdriver with a 6″ to 8″ blade, push the intake plate away from its seat (down) to unload valve. It may take a slight bump with the heel of your hand to do so.
  • A continuing rush of air from the unloaded valve indicates discharge plate damage and the valve should be replaced. A continuing airflow from booster valve with the intake not held open indicates a leaking intake O-ring and the O-ring should be replaced.
  • A damaged or broken discharge plate in the booster valve will let compressed air leak back into the cylinder and, on the down stroke of the piston, allows compressed air to go past piston rings and enter into crankcase causing excessive crankcase pressure and premature ring wear. 
Note: An early sign of leaking discharge valve is higher than normal induction pressure on booster gauge.
  • At first sign of excessive crankcase pressure, the booster valves should be checked i.e. oil blowing out dipstick or fill cap, or excessive engine oil consumption.
  • If booster valves check O.K., unit should be run at 1800 rpm with rig air supply disconnected and discharge airline disconnected with intake and discharge valve open (no air being compressed). If excessive crankcase pressure still exists, the problem is on the power side of the engine.
  • If, upon completion of step 7, excessive crankcase pressure does not exist, booster cylinders should be removed and pistons, rings, and cylinders should be checked for damage or excessive wear.