Sauer-Danfoss (Sundstrand) Series 45 Open Circuit Pump Rebuild Guide: Seal Kits, PC and LS Settings, Torques and Start-Up

To rebuild a Sauer-Danfoss Series 45 open circuit piston pump, identify the frame (E, F, G, H, J, K, L or K2) from the model code, replace the snap-ring retained shaft seal, strip and clean the LS/PC control, then remove the end cap for the rotating group and fit the overhaul seal kit for that frame. After start-up, reset the pressure compensator (PC) and load sense (LS) settings with gauges, because the per-turn gain and the control screw torques are different from frame to frame.

The factory draws the same line on every frame: the Series 45 service manuals cover installation, adjustment and minor repair, and Danfoss says major repairs require removing the end cap, which voids the warranty unless an Authorized Service Center does the work. Minor repairs also require pulling the pump from the machine.

Which Series 45 frame do you have?

The frame letter starts the displacement part of the model code (J45B, F74B, K38C and so on). The serial number gives the plant, year and week: A is Ames, Iowa, N is Neumunster, Germany, and the K and J parts manuals show S and DC for Slovakia. The year and week matter, because Danfoss parts lists give the same item different part numbers by date code. Our Sundstrand and Sauer-Danfoss identification guide explains how to read the tag.

Frame	Displacements	Mounting	Service manual
L	25 and 30 cm³	SAE-B	520L0532
K	38 and 45 cm³	SAE-B	520L0532
K2	25, 30, 38 and 45 cm³	SAE-B	AX00000301
J	45, 51, 60, 65 and 75 cm³	SAE-B 2 bolt, SAE-C 4 bolt	520L0607
H	57 and 75 cm³	SAE-B, SAE-C	520L0611
G	74 and 90 cm³	SAE-C	520L0605
F	74 and 90 cm³	SAE-B 2 bolt, SAE-C 4 bolt	11005158
E	100, 130 and 147 cm³	SAE-C	520L0606

All frames share the same basic design: a bias spring pushes the servo piston to full stroke, and the control meters system pressure to the servo piston to bring the swashplate back. Controls are PC only, remote PC, LS with PC, or electric. Every manual lists the same case pressure limit, 0.5 bar (7 psi) above inlet continuous and 2 bar (29 psi) at cold start, and inlet pressure of at least 0.8 bar absolute continuous and 0.5 bar absolute at cold start. Our load sensing pump guide explains how the LS and PC spools work together.

Is it the pump, or the system around it?

The Series 45 troubleshooting tables send you to the system first:

Symptom	Check first (per Danfoss)
Pressure will not reach the PC setting	The PC setting itself, an external relief set below the PC setting, a broken PC spring, a worn or reversed PC spool, or contamination in the control.
Low output flow	Oil level, viscosity, external relief below PC, low PC or LS setting, high inlet vacuum, low input speed, and wrong rotation.
Pressure or flow instability	Air in the system, sticking control spools, a low LS setting, a blocked LS signal line, too little gap between the PC setting and the external relief, or a chattering relief.
Sluggish actuators	Relief setting, PC and LS settings, LS signal, high case pressure from a restricted drain line, inlet vacuum, and worn internal parts.
Noise or vibration	Oil level, air, inlet conditions, loose or wrong couplings, and shaft alignment.

The external relief must always be set above the PC setting, or the relief, not the pump, sets system pressure and you chase a pump problem that is not there. On fan drive pumps, the J frame manual asks for at least 15 bar between the PC setting and any system relief. Our case drain flow test is the best check for internal wear before teardown, and how to tell pump rotation covers the rotation question.

How do you replace a Series 45 shaft seal?

Every frame uses a lip seal held by a retaining ring, and Danfoss says it can be replaced without major disassembly once the pump is off the machine.

1. Remove the retaining ring (K010) with snap ring pliers.
2. Puncture the seal face with a packing hook or use a slide-hammer puller, and remove the seal (K020) without marking the housing or shaft. Some pumps have a second seal; take it out too.
3. Inspect the housing bore and the new seal, and check the shaft sealing area for rust, wear or contamination. Polish the shaft if needed.
4. Lubricate the new seal lip with clean hydraulic fluid and put a protective sleeve over the shaft end.
5. Press the seal in square to the shaft, cupped side toward the bearing, only far enough to clear the retaining ring groove. Pushing it into the bearing causes premature bearing failure.
6. Refit the retaining ring and remove the sleeve.

On H and J frames, SB-2006-005 replaced shaft lip seal 5000190 with 5000702 from serial A-06-15; the two interchange.

How do you rebuild the LS and PC control?

On the E, F, G, J, K, L and K2 frames the control is a separate housing held by four screws (C300) with four interface seals (C200), three on the K and L frames. Remove the PC set screw, adjusting plug, springs and seat, then the plug and PC spool, noting which way the spool faces. On LS controls do the same for the LS side. Then inspect:

• Adjusting plug tips and the faces where they meet the spring seat.
• Springs and spring guides for wear or damage.
• Spool sealing lands for nicks and scratches, and the spool ends where they contact the guides.
• Spool bores in the housing for excessive wear.

Lubricate the spools, springs, guides and new O-rings with clean hydraulic fluid. Install each spool spherical end first, thread the adjusting plug in flush plus one full turn as a starting point, fit new interface seals with petroleum jelly, and torque the control screws in a crisscross pattern, then re-torque the first screw. Reset the control with gauges afterward.

The H frame is different: its PC valve is a cartridge in the pump, with a bias piston plug and servo piston plug that Danfoss torques to 175-245 N·m (120-170 lbf·ft) and warns can back out if under-torqued. The new style one-piece PC cartridge goes in at 27-47 N·m and does not come preset.

What are the PC and LS adjustment rates and control torques by frame?

Frame	PC gain per turn	LS gain per turn	Control screws (C300)	PC/LS set screw or lock nut
E	42 bar (610 psi)	17 bar (250 psi)	5.4-7.5 N·m (4-5.5 lbf·ft)	7.5-10.8 N·m (5.5-8 lbf·ft)
F	42 bar (610 psi)	17 bar (250 psi)	6 N·m (5 lbf·ft)	9 N·m (7 lbf·ft)
G	42 bar (610 psi)	17 bar (250 psi)	5.4-7.5 N·m (4-5.5 lbf·ft)	7.5-10.8 N·m (5.5-8 lbf·ft)
H	57 bar (825 psi)	18 bar (260 psi)	PC cartridge, see above	7.5-10.8 N·m (5.5-8 lbf·ft)
J	42 bar (610 psi)	17 bar (250 psi)	6 N·m (5 lbf·ft)	9 N·m (7 lbf·ft)
K and L	35 bar (507 psi)	12 bar (170 psi)	15-18 N·m (11-13 lbf·ft)	9 N·m (7 lbf·ft)
K2	35 bar (507 psi)	12 bar (170 psi)	6 N·m (5 lbf·ft)	9 N·m (7 lbf·ft)

Sources: the adjustment and LS/PC control repair sections of each frame's service manual (E pages 24-32, F 26-35, G 21-26, H 21-22, J 24-34, K and L 22-29, K2 24-31). The E, F and J manuals also print a pressure change table with lower per-turn gains for some other control codes, so check that table if your code is not a standard LS or PC control. Hydraulic LS/PC control screws are the ones listed; electric controls on the same frames use slightly different values in their own sections.

Setting PC: gauge system pressure at M1 and case pressure at L1 or L2, warm the oil, and dead-head a function so the pump is at maximum pressure and zero flow. Loosen the set screw or lock nut, turn the PC plug (clockwise raises), and lock it. The PC setting is referenced to case, so subtract case pressure from the M1 reading. Setting LS: tee a gauge into the LS signal line at port X, run a function at about half flow with pressure below the PC point, and set the difference between M1 and X. Then set PC. J frame pumps with a radial end cap have no M1 port, so read system pressure as close to the pump as you can. Our pump pressure adjustment guide covers the general method.

Which overhaul seal kit does a Series 45 pump take?

Frame	Current overhaul seal kit	Replaced kit	Bulletin and effective serial
E	11106334	11034352	SB-2012-029, A-13-10
F	11106335	11034341	SB-2012-029, A-13-10
G	11106336	11034340	SB-2012-029, A-13-10
H	11106337	4510094	SB-2012-029, A-13-10
J	11103473	11032927	SB-2011-031, A-12-04
K and L	11106339	11034353	SB-2012-001, A-12-10

On the E, F, G, H, K and L frames, the newer kits only drop the standard plug O-rings and interchange with the old kits. The J frame change is one way: the new kit adds the new style servo piston seal ring and fits older pumps, but the old kit cannot be used on newer pumps. We do not list these kits as stocked parts; send us the full model code and serial number and we reply with price, availability and lead time. Other Sundstrand kits we carry are in the Sundstrand seal kit collection, and the Sundstrand seal kit guide explains how we match them.

Inside the pump, bulletins also cover rotating group, valve plate, servo piston and end cap changes by frame (for example SB-2012-024 rotating group and SB-2010-033 servo piston on the J frame, SB-2001-023 low noise end cap and valve plate on the K frame). In our shop we keep the valve plate with its end cap and each rotating group together, and treat a scored block or valve plate face, or a loose slipper, as a parts decision. Danfoss publishes no figures for those calls.

How do you start up a rebuilt Series 45 pump?

1. Couple the pump to the prime mover with the shafts properly aligned. Misalignment damages the shaft, bearings or seal.
2. Fill the reservoir through a 10 micron filter and never reuse fluid.
3. Fill the pump housing with clean oil through the uppermost case drain port, and run the case drain line from that uppermost port so the pump stays full.
4. Fill the inlet line and check it for loose fittings, restrictions and air leaks.
5. Gauge the system pressure port, then jog the prime mover or run at the lowest speed until system pressure builds to normal, at least 11 bar (160 psi). If it will not hold, shut down and find out why.
6. Run the system at least fifteen minutes under light load, then check and adjust the PC and LS settings.
7. Shut down, remove the gauge, refit the plug, and top up the reservoir.

Danfoss calls for cleanliness of ISO 4406 18/13 or better, and fluid and filter changes at no more than 2000 hours with a sealed reservoir or 500 hours with a breather. See our start-up procedure guide, fluid cleanliness guide and oil viscosity guide.

Should you rebuild a Series 45 pump yourself?

The shaft seal and the LS/PC control are bench jobs, and a lot of Series 45 "pump failures" end there once the control is cleaned and set with gauges. Opening the end cap is a different job. If case flow is high, the pump is noisy at normal inlet conditions, or there was metal in the filter, have it torn down and quoted before you buy a kit. These pumps often share a machine with a Series 90 hydrostatic pump or a Series 51 motor, and contamination usually reaches all of them.

Frequently asked questions

Related reading

• Sundstrand Series 90 pump rebuild guide
• Series 51 bent axis motor rebuild guide
• Series 90 motor rebuild guide
• Sauer-Danfoss Series 90 model code decoder
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• All guides and resources