VALVE GP-RELIEF 4T1575 - Caterpillar

Engines, 3500, 3600 Families Of Engines Equipped With Air Starting AttachmentDescription of Change: An improved air starter relay valve provides increased retention of valve spool O-ring seal (2). The groove for the O-ring has been made deeper to help keep the O-ring in place. A seal which is out of its groove could allow air to leak past the closed relay valve and cause the air starter pinion to turn. This could cause the starter pinion to try to engage a flywheel ring gear. This could result in damage to the pinion and ring gear.
Location of O-ring seal (2) and Date Code (1) on 4N3411 Air Starter Relay Valve.Adaptable To: The part number of the improved 4N3411 Air Starter Relay Valve has not changed. The improved valve can be identified by the three letter date code stamped on the valve body. See the illustration. All valves date codes November 1989 or later have the improvements. The first letter in the date code indicates the supplier manufacturing plant; the second letter indicates the year of manufacture; and the third letter indicates the month of manufacture. Chart A provides the codes for years and Chart B provides the codes for months.
Example: A valve coded "WQH" is manufactured at the plant indicated by the letter "W". The letter "Q" indicates the year of 1990. The letter "H" indicates the month of August.
Example: A valve coded "WPL" is manufactured at the plant indicated by the letter "W". The letter "P" indicates the year of 1989. The letter "L" indicates the month of November.