Originally Posted by beamertruck

thats because your releasing the pressure, can actually hydrolock the motor, so try not to remove the cap while its running if you dont have to, if you do only do so for a little while. Injectors on our 4.4s can get pretty loud with age, usually its due to build up, mine have been running decently quieter since ive started the Amsoil treatments. Nice thing is it will also bring oil consumption down if not eliminate it, since it also has Upper Cylinder Lubricant you eliminate the need for oil to have to go through. (little known fact behind oil consumption)