ROD 7N1632 - Caterpillar

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.
This Program must be administered as soon as possible. When reporting the repair, use "PI3735" as the Part Number, "7751" as the Group Number, "56" as the Warranty Claim Description Code and "T" as the SIMS Description Code. Exception: If the repair is done after failure, use "PI3735" as the Part Number, "7751" as the Group Number, "96" as the Warranty Claim Description Code, and "Z" as the SIMS Description Code.
Completion Date
June 30, 1995Termination Date
December 31, 1995Problem
There is a possibility of unequal pressure build up in the boom cylinder on certain 350, 350L, 375 and 375L Excavators. The check valves have a small orifice plug that may come loose because of improper assembly. In the "boom down" mode, if the orifice plug is loose in one of the valves, pressure in that cylinder will not release and may cause damage to the rod and cylinder assembly. If the orifice plug comes loose in both valves, the boom may lower slowly or may not lower at all.
Affected Product
Model & Identification Number
350 (3ML118, 3ML127-128, 3ML133, 3ML149, 3ML154, 3ML175, 3ML193-194, 3ML205, 3ML208, 3ML218-219, 3ML221-223, 3ML227-228, 3ML234, 3ML248, 3ML250, 3ML276-277, 3ML358-359, 3ML370, 3ML375, 3ML377-378, 3ML381)
350L (9FL97-98, 9FL101, 9FL103, 9FL105, 9FL107, 9FL109, 9FL123, 9FL125-126, 9FL130-131, 9FL133, 9FL135-136, 9FL142-143, 9FL145-146, 9FL148-149, 9FL158, 9FL165, 9FL170-171, 9FL187-188, 9FL192, 9FL194)
375L (1JM36, 1JM38, 1JM59, 1JM64, 1JM66, 1JM91, 1JM97, 1JM99, 1JM101-102 9WL39 , 9WL44, 9WL47, 9WL49, 9WL52-55, 9WL60, 9WL65, 9WL69-73, 9WL75-80)
Parts Needed
Not applicable
Action Required
See the attached rework procedure.
Owner Notification
U.S. and Canadian owners will receive the attached Owner Notification.
Service Claim Allowances
This is a 4 hour job.
U.S. and Canadian Dealers Only - Eligible dealers may enter a Type 2 SIMS Report.
Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
MAKE EVERY EFFORT TO COMPLETE THIS PROGRAM AS SOON AS POSSIBLE.
Attach.(1-Owner Notification)(2-Rework Procedure)Copy Of Owner Notification For U.s. And Canadian Owners
Rework Procedure
Disconnect the lines and remove both check valves from the boom cylinders Remove the 1R5206 Cover from each vale group. Check the "break away" torque on the orifice plug by applying a proof-load of 25in/lb.
If the orifice plug remains tight (no movement of the orifice plug while under sustained proof-load):
1. Reassemble the check valve2. Install the valve back on the cylinder and attach the lines.If the orifice plug becomes loose:
1. Remove the orifice plug from the valve.2. Clean the old thread tightening compound and any oil residue from the orifice plug and the valve. Clean the threads with primer and apply thread tightening compound.3. Tighten the orifice plug to a torque of 25 in/lb. Allow the thread tightening compound to cure before assembly of the top cover back onto the valve.4. Install the valve back on the cylinder and attach lines.