Hydro-Gear Pumps: PG, PK, PE, PR, PW Series Explained
Short version: Hydro-Gear's P Series are commercial axial-piston, variable-displacement pumps, named by a two-letter prefix that tells you the size: PC 6.1 cc, PG/PE 10.2 cc, PL 10 cc, PJ/PK 12 cc, PR 16 cc, PW/PY 21.8 cc. Some carry older BDP names in Hydro-Gear's cross-reference (PG = BDP-10A, PR = BDP-16A, PW = BDP-21L, PL = BDP-10L). The model number is on a label on the pump housing. Hydro-Gear calls them maintenance-free; oil follows the vehicle maker's recommendation, and the bypass screw opens two turns at most.
P Series pumps at a glance
| Prefix | Displacement | Older name | Input speed, max / min (rpm) | Pressure, continuous / intermittent / peak (psi) | Flow at 1000 psi, 3000 rpm |
|---|---|---|---|---|---|
| PC | 6.1 cc (0.37 in³) | — | 3600 / 1800 | 750 / 1750 / 2500 | — |
| PG / PE | 10.2 cc (0.62 in³) | PG = BDP-10A | 3600 / 1800 | 1000 / 2100 / 3500 | PG: 7.6 gpm |
| PL | 10 cc | BDP-10L | not confirmed | not confirmed | — |
| PJ / PK | 12 cc (0.73 in³) | — | 3600 / 1800 | 1000 / 2100 / 3500 (PK) | PK: 8.9 gpm |
| PR | 16 cc (0.97 in³) | BDP-16A | 3600 / 1800 | 1250 / 2500 / 3750 | 12 gpm |
| PW | 21.8 cc (1.33 in³) | BDP-21L | 3600 / 1800 | 1250 / 2500 / 3750 | 16.4 gpm |
| PY (and PY with 6 cc auxiliary pump) | 21.8 cc (1.33 in³) | — | 3600 / 1800 | 1500 / 2750 / 3750 | 16.4 gpm |
Sources: Hydro-Gear's pump page and Cross Reference Guide; flow figures from the BLN-52503 P Series manual. A dash means the figure isn't in the Hydro-Gear sources we used. Unit weights in the manual run from about 7 lb to 17 lb across the range.
Operating limits (all P Series)
- Inlet filtration: 25 micron nominal. An inlet filter is required; use the vehicle maker's approved filter.
- Maximum inlet vacuum: 4 in Hg.
- Normal operating temperature: -10 to 200 F; 230 F maximum intermittent.
What the series have in common
Hydro-Gear describes its pumps as "smooth, efficient, and maintenance-free." They're axial-piston, variable-displacement pumps with a cradle swashplate. Features across the range: fixed-displacement charge pumps, check or shock valves, a return-to-neutral device, tandem and auxiliary-pump options, and an optional cooling fan.
PG vs PE: same 10.2 cc displacement. The PG has a valve plate; the PE has none (the manual says to lubricate the PE's end cap face during assembly).
Finding your pump's model number
The label is on the pump housing. A current P Series model number looks like PC-AGCC-MV1X-XXXX: the first two letters are the series from the table above. Older BDP pumps carry labels such as BDP-10A-300; the BDP-10A, BDP-16A and BDP-21L are 10.2, 16 and 21.8 cc pumps rated for 1800–3600 rpm input. Order by the complete number, not just the prefix. More on labels: how to find your Hydro-Gear part number.
Left and right pumps
RFQQQ's ordering advice: if your machine has two pumps, one for each drive wheel, read the label on each one. Order each by its own model number and tell us which side it came from. Don't assume the left and right pumps share a number.
Oil and the bypass
- Oil: Hydro-Gear's pump manuals are less specific than its transaxle manuals. They call for engine oil with a minimum of 55 SUS (9.0 cSt) at 230 F, API SJ/CD, and say to follow the vehicle manufacturer's recommendation. Use what your mower's manual specifies.
- Bypass: a screw-type valve, "fully opened when unscrewed two (2) turns maximum." It must be fully closed (clockwise) during normal operation.
- Purging: the general Hydro-Gear purge procedure applies (bypass open, cycle forward and reverse 5–6 times; bypass closed, cycle again; check and top up). The P Series manual adds that purging is complete when the reservoir level also stays constant. Steps: how to purge a Hydro-Gear system.
- Flow testing: Hydro-Gear's Flow Test Kit is part 70661. Don't exceed 2600 rpm input when testing PW or PY pumps.
Pump rebuild kits and parts
Hydro-Gear's free BLN-52503 P Series service and repair manual has the exploded views and parts lists. We carry Hydro-Gear repair and seal kits and replacement parts; send us the pump's model number and we'll confirm which kit or part matches it.
Shop Hydro-Gear pumps (PG, PK, PE, PR, PW, PL) or send us the number through the Hydro-Gear part finder.
Frequently asked questions
How do I know which Hydro-Gear pump I have?
Read the label on the pump housing. The first two letters of the model number (PC, PG, PE, PJ, PK, PR, PW, PY) give the series and displacement; the full number identifies the exact build.
Is a Hydro-Gear BDP-10A the same as a PG pump?
Hydro-Gear's Cross Reference Guide lists the PG as the BDP-10A. Likewise, the PR is the BDP-16A, the PW is the BDP-21L and the PL is the BDP-10L. Send us the full BDP label number and we'll match the current part.
What is the difference between a PG and a PE pump?
Both are 10.2 cc. The PG has a valve plate and the PE does not.
What oil goes in a Hydro-Gear pump?
Follow the vehicle manufacturer's recommendation. Hydro-Gear's pump manuals set a minimum of 55 SUS (9.0 cSt) at 230 F, API SJ/CD engine oil.
How far do I open the bypass on a Hydro-Gear pump?
Unscrew it two turns at most; that opens it fully. Close it fully (clockwise) before normal operation.
Sources: Hydro-Gear Pumps, Cross Reference Guide; BLN-52503 P Series service and repair manual; Toro-hosted copies of BLN-52503 (2014) and BLN-51337 BDP pumps (2003).
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