ROD 8H5321 - Caterpillar

Illustration 1 g03363206
(1) Valve as (2) Plug (3) Loosen locknutWhen the inner valve assembly is loose, the return line pressure of the boom cylinder cannot be regulated properly because the stroke of the valve shaft is restricted and erratic movement can occur. If you experience erratic boom movement, the return check valve should be replaced. The improvements to the return check valve with the Loctite to the inner valve assembly has been made on the assembly line.
Illustration 2 g03363207
The improved return check valve can be identified by the alphabet on the body of the valve as shown in Illustration 2. The part numbers of the check valve group have stayed the same even with the improvement. Refer to Table 1 for the correct part number and stamp letter for your machine.
Table 1
Sales Model    Prefix    Valve Gp Part Number    Stamp letter    
320D RR/LCR     AMR, CWN, DHE, EBY, EJT, FXK, GKL, GMX, HJC, RBL, SCW, TAE, SCK YDS, ZGB     171-0098     C    
321D CR/LCR     JCX, KBH, KBZ, MDT, MPG, NAS, PBD, TXA    
328D LCR     BYH, GTN, MKR, RMX, SWF    
320D LN     KAF, PCX, WBN     173-4672     D    
323D L/LN/S/SA     CWG, CYD, DKW, NES, PBM, RAC, SDC, SED    
324D L/LN     AWN, BTK, BYE, CJX, DFP, ECH, EJC, GPK, JAT, JJG, JZR, LAB, MND, PYT, SYM, T2D, TRH, TSN    
325D L     A3R, AZP, CJM, CYW, DAP, DBH, ERK, GBR, GPB, KBE, KDG, LAL, MCL, NAC, PAL, PEH, PKE, SCR, T2S    
326D L     PJM    
329D L/LN     BBF, BFC, BYS, CZF, DJF, DTZ, EBM, JHJ, LFW, MNB, RSK, SCY, TAY, TPM, TZL, WDK, WLT, XDB, YFW    
330D L/WH     B6H, EAH, EDX, ERN, FFK, GBC, GGE, HAS, JJM JLP, KAB, LCJ, LDR, LRM, MEY, MWP, NBD, NEF, PCK, PFC, R2D, RAS, RDA, RDK, THJ     190-7745     E    
336D L/LN     DTS, EMX, J2F, JBF, JBT, JER, JWR, KDJ, KKT, LMG, M4T, MDS, MPL, MYG, MYP, NLS, PGW, PPN, PRF, PTB, SKE, W3K, WET, WRK, ZML    
340D L     JTN    
320E L/LN     AWS, SXE, KLT, LAK, NAZ, REE, TNJ, WBK, DFG     335-0300     C    
323E L/LN/SA     RAP, TDW, YRP    
324E L/LN     JCZ, KTE, PNW, TLF, LDG    
329E L/LN     PTY, PLW, RDX, TST, WJK, ZCD, RLD    
336E L/LN     CMR, KED, BZY, FJH, GTJ, JRJ, TEG, YCE, YEP, TMZ    
320E RR/LRR     LHN, MEW, PNL, TFX     335-0305     B    
345D L/LC-VG     BYC, BYW, DPA, EEH, FES, HLC, JKN, KFH, LKY, MLK, NEG, NLM, PBT, RAE, RAJ, RGD, RGG, YEE     335-0374     B    
349D L/LC-VG     GKF, JGB, KHS, KLH, MEN, NNF, PZG, RBJ, WTD    If the former check valve group is needing reworked, the following procedure should be followed.
Disassemble the inner valve assembly from the valve group.
Illustration 3 g03363212
Apply 9S-3263 Thread Lock Compound and reassemble the inner valve assembly in the valve group and install