HARNESS AS-TRANSMISSION 2193035 - Caterpillar

Caterpillar: Confidential Yellow
TWO PROGRAMS EXTENDED TO REDUCE CYLINDER HEAD CRACKING - OCTOBER 4, 1982; PIP125 REPLACED BY OPTIONAL PIP ON ADDITION OF ORIFICE PLATES TO WATER LINES - 992C (42X) LOADERS; 772B TRACTORS, 773B TRUCKS - PI7097 - MAILED US AND CANADA, COFA, CFEL
  The information supplied in this service letter may not be valid after the termination date of this program.   Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
TWO PROGRAMS EXTENDED TO REDUCE CYLINDER HEAD CRACKING October 4, 1982; PIP125 Replaced By Optional PIP On Addition of Orifice Plates To Water Lines - 992C (42X) Loaders; 772B Tractors, 773B Trucks , PI7097 U-47 AU-39 E-28 Refer to the above Service Letter and write "OPTIONAL PI7097" by the title. Cross out PIP125 as this number is canceled. Add a NOTE referring to this Service Letter. This Program is extended to May 31, 1985. Field data shows a significant reduction in cracking of the cylinder head bottom deck on precombustion chamber engines that have the orifice plates. The possibility of pump cavitation is reduced. Also, air bubbles in the coolant collect in the top tank where it is forced out the overflow line. On Page 2, Illustration 1, add a Note to simply deburr the 28.6 mm hole, not to remove the sharp edges. Some dealers have reported that heads cracked after orifice plates were installed in the field. It is possible that these heads had minute cracks before the orifice plates were installed. Further operation probably slightly enlarged the cracks and leaks occurred. : If you install a replacement engine, be sure the orifice plates are in both outlet water lines between the engine and radiator. See Illustration 3 in October 4, 1982 Service Letter. Install the orifice plates if not present. January 14, 1983; PIP380 - Install Water Orifice Plates In Direct Injection Engines In 631D, 633D, 637D, 639D Tractors Orifice plates in the water outlet lines on these engines are also reducing the likelihood of cylinder head cracking. Refer to Page 3 and change the Termination Date to May 31, 1985. Also, make a change on Page 2. Cross out the "45 deg. Chamfer Both Edges", and replace with these machining instructions: "Deburr the hole." Chamfering the hole tends to reduce the flow resistance and permit too much coolant to flow through the hole.