Seals Parts
199 products available
Pump water seals separate the pumped fluid from the crankcase oil. When they fail, you'll see water in the oil (milky, cloudy) or oil leaking past the plunger — and seal life depends heavily on water quality, since sediment and hard water dramatically shorten it. When you replace water seals, replace the oil seals and o-rings in the same kit at the same time; they wear on the same schedule and the labor to access them is identical either way.
0007.43 OIL SEAL
SKU: 6083
SKU 6083 — oil seal #0007.43: retains crankcase oil and excludes water; confirm the part number on your pump's parts diagram and replace with fresh oil.
0009.0106.00 BRASS PACKING
SKU: 1645
SKU 1645 — high-pressure water seal packing #0009.0106.00 for triplex plunger pumps; confirm the part number and your plunger diameter against your pump's parts diagram.
0019.0058.00/19.0103.00 SEALING RING AXDPUMPS
SKU: 3979
0019.0058.00/19.0103.00 SEALING RING AXDPUMPS is a sealing ring #0019.0058.00 for AXD pumps. SKU 3979.
0019.0095.00 OIL SEAL (NEED 3/PUMP)
SKU: 1637
Comet 0019.0095.00 15 x 24 x 5 mm plunger oil seal for LW/LWS/LWR/LWD/ZWD pumps (SKU 1637; 3 needed per pump).
100488 SEAL, OIL, C/C, NBRS 35FR, 35, 38PF
SKU: 1943
Site SKU 1943 is the CAT Pumps 100488 Buna crankcase oil seal for 3570 pumps.
1080401 BACK-UP RING
SKU: 3530
SKU 3530 — back-up ring #1080401: closes the clearance gap so seals can't extrude under pressure; match the part number to your pump's parts list.
125351 SEAL, OIL
SKU: 3924
CAT Pumps 125351 nitrile oil seal for 66DX, 3SPX, and 67DX pumps (SKU 3924).
1940560 SEAL
SKU: 3060
SKU 3060 — replacement pump seal #1940560; match the part number to your pump's exploded diagram or data plate, and replace seals as a matched set.
20189 BACK-UP-RING, PLGR, PTFE
SKU: 2788
Site SKU 2788 is the CAT Pumps 20189 PTFE plunger-retainer backup ring.
20213 BACK-UP-RING, VPG, PTFE
SKU: 2794
Site SKU 2794 is the CAT Pumps 20213 valve-plug backup ring for 56/57/60 pumps.
21985 BACK-UP RING, (TEFLON)
SKU: 5151
Site SKU 5151 is the CAT Pumps 21985 cylinder backup ring for 331/333/335 pumps.
21986 BACK-UP RING, (TEFLON)
SKU: 5152
Site SKU 5152 is the CAT Pumps 21986 cylinder backup ring for the model 323 pump.
25301 OIL SEAL, CRANKCASE (BUNA-N)
SKU: 2689
Site SKU 2689 is the CAT Pumps 25301 NBR oil seal for 4SP pumps.
25461 OIL SEAL, CRANKCASE (BUNA-N)
SKU: 2886
CAT Pumps 25461 Buna-N crankcase oil seal for 2SF-series and 250/260 pumps — SKU 2886.
27339 OIL SEAL (BUNA-N)
SKU: 2854
Site SKU 2854 is the CAT Pumps 27339 crankcase oil seal for 621/623/820/821/1010/1011 pumps.
2745 SUPPORT RINGS RC SERIES
SKU: 6335
SKU 6335 — support ring #2745 for RC series pumps: backs up the packing set in each cylinder's seal stack; confirm it on your RC series parts diagram.
28204 BACK-UP RING, CYLINDER TEFLON 10FR
SKU: 2938
Site SKU 2938 is the CAT Pumps 28204 cylinder backup ring for 621/623/820/821 pumps.
29003 BACK-UP RING, SLEEVE (TEFLON)
SKU: 5155
Site SKU 5155 is the CAT Pumps 29003 PTFE backup ring for 621/623/820/821/1010/1011 pumps.
30305 SEAL KIT 4FR 10FR 280 290 323 390
SKU: 3367
Site SKU 3367 is the CAT Pumps 30305 seal kit for 621/623/820/821/1010/1011 pumps.
30312 KIT, SLEEVE & SEAL 1/PUMP
SKU: 3981
Site SKU 3981 is the CAT Pumps 30312 NBR sleeve-and-seal kit for 323 and 331/333/335/430/431/435 pumps.
30315 SEAL, IM, NBR, PRRRRRM-A-LUB
SKU: 5599
Site SKU 5599 is the CAT Pumps 30315 NBR low-pressure seal for 623/820/1010/621/821/1011 pumps.
30397 KIT, SLV & SEAL, NBR
SKU: 5613
Site SKU 5613 is the CAT Pumps 30397 prrrm-a-lube sleeve-and-seal kit for 10-frame pumps.
30431 SLEEVE & SEAL KIT FOR 280-290
SKU: 3366
Site SKU 3366 is the CAT Pumps 30431 kit for the model 281 pump.
Seals Buying Guide
Full kit vs. individual seals
Seal kits are almost always cheaper per-seal than ordering individual o-rings, and since you have to disassemble the same section of the pump either way, replacing the full kit instead of one worn seal avoids a second teardown a few months later.
Matching the kit to your pump
Seal kits are sized to a specific pump model and plunger diameter, not a generic "fits most" spec. Confirm your pump's exact model number and plunger diameter (in mm) before ordering — this is the single most common ordering mistake.
Water quality shortens seal life
Commercial operators on well water or hard municipal water should expect to replace seal kits more often than the manual's stated interval suggests. An inline filter ahead of the pump inlet reduces sediment-driven wear.
Seals FAQ
How do I know my seals have failed?
Milky or cloudy pump oil is the clearest sign — that's water that's worked past the water seal into the crankcase. Oil visibly leaking from the base of the pump near the plunger is the other common symptom.
Is it safe to mix OEM and aftermarket seals on the same pump?
Yes, as long as each part matches your pump's exact model specifications. Mixing brands isn't the risk — mismatched sizing is.