Learning how to install a hydraulic pump on a skid steer is DIY-friendly, but you need clean working conditions and proper pump priming to protect your new part. Keep reading for our step-by-step installation guide and key pro tips.
Understanding Your Skid Steer’s Hydraulic Pumps
Before you start turning wrenches, it helps to know exactly what you are replacing. Most modern skid steers utilize two main types of hydraulic pumps, often bolted together in a tandem setup.
| Feature | Gear Pump (Implement Pump) | Hydrostatic Piston Pump (Drive Pump) |
|---|---|---|
| Primary Function | Powers the loader arms, bucket tilt, and auxiliary attachments. | Powers the drive motors that move the tracks or wheels. |
| Complexity | Simple, durable, and relatively inexpensive. | Highly complex, operates at extreme pressures, and expensive. |
| Failure Symptoms | Slow lifting, weak breakout force, stalling under heavy loads. | Machine won’t drive, sluggish turning, loud whining/growling noises. |
| Installation Note | Usually straightforward bolt-on replacement. | Requires strict case-filling and priming procedures to prevent dry starts. |
Pre-Install Preparation
Tools
- Wrench and Socket Set: Standard and metric, plus line wrenches for hydraulic fittings.
- JIC Caps and Plugs: Absolutely essential for capping open hoses and keeping dirt out.
- Torque Wrench: To tighten mounting bolts to factory specs.
- Clean Drain Pans: Large enough to hold 10 to 20 gallons of fluid.
- Fresh Hydraulic Fluid: Check your manual for the correct spec (e.g., AW46, 10W-30 motor oil, or OEM specific).
- New Hydraulic Filters: Never install a new pump on old, dirty filters.
- O-Rings and Seals: Often included with the new pump, but verify beforehand.
- Brake Cleaner and Rags: Lint-free shop towels are best.
Safety Prep
Hydraulic systems work at thousands of PSI. Pressurized fluid can punch straight through your skin and cause bad injuries.
- Secure the Machine: Park on flat, level ground. Drop the bucket or attachment all the way down to the ground.
- Support the Lift Arms (If Raised): If you need to lift the cab or lift arms to get to the pump, lock in the factory support strut. Never count on hydraulic cylinders to hold the arms up when you’re working underneath.
- Kill the Power: Turn off the engine, pull out the key, and disconnect the negative battery cable.
- Relieve Pressure: Move the joysticks every direction to bleed trapped pressure from the implement lines. Slowly loosen the hydraulic tank breather cap to release tank pressure.
How to Install a Hydraulic Pump on a Skid Steer?
Note: Every machine is a little different. On a Bobcat S130, you may need to loosen engine mounts and shift the engine back just enough to slide the pump out. A John Deere 320D may let you reach it directly. Always check your machine’s service manual.
Step 1: Drain the Hydraulic Fluid
Set drain pans under the hydraulic reservoir drain plug. You might not need to empty the whole tank depending on where the pump sits, but draining everything is strongly recommended for a fresh start. If your old pump failed internally, metal shavings likely got into the fluid.
Step 2: Clean, Label, and Disconnect Hoses
Before loosening any fittings, spray brake cleaner all around the pump. Get this area totally clean.
- Snap photos of how the hoses run with your phone.
- Use zip ties or tape to mark each hose and its port (Inlet, Outlet, Case Drain, etc.).
- Take the hoses off and cap the hose ends and pump ports right away.
Step 3: Remove the Old Pump
Take out the mounting bolts holding the pump to the engine flywheel housing or tandem pump assembly. Slide the pump straight back carefully to separate the splined shaft or Lovejoy coupling.
Mechanic Tip: Pumps are heavy and hard to handle. Ask a friend to hold its weight, or use a small ratchet strap while you remove the final bolt.
Step 4: Prep the New Pump and Replace Seals
Lay the old pump next to the new one on a clean workbench.
- Double-check that the shaft splines, mounting flange and port sizes match perfectly.
- Move any required adapter fittings from the old pump to the new one. Fit new O-rings on these adapters. Skip Teflon tape on hydraulic fittings unless the manual says otherwise — it can tear up and clog valves.
- Coat the pump shaft splines with good anti-seize or clean grease.
Step 5: Mount the New Pump
Slide the new pump into place gently. Don’t force it. The splines should fit smoothly. If it sticks, turn the pump shaft a little until it slides home.
- Thread mounting bolts in by hand first to avoid stripped threads.
- Tighten bolts using a crisscross pattern.
- Use your torque wrench to hit the exact values from your manual. For example, some Bobcat gear pumps need 55 to 60 ft-lbs. Guessing can crack flanges or leave the pump loose.
Step 6: Reconnect Hoses and Fill the System
Take off the caps and hook the hydraulic lines back onto their correct ports. Tighten firmly, but do not over-tighten — too much force crushes O-rings and causes leaks. Install new hydraulic filters, then fill the reservoir with fresh hydraulic fluid up to the sight glass mark.
Step 7: Prime the Pump (Do Not Skip This!)
If you fit a hydrostatic piston pump, it has a case drain port at the top. Remove this fitting and pour clean hydraulic fluid straight into the pump housing until it is fully filled. Never fire up a dry piston pump. Its internal brass slippers will scratch the swashplate in seconds and destroy your brand-new pump.
Step 8: Test and Inspect
Don’t start the engine at full throttle.
- Crank the engine a few times without letting it fire (pull the fuel shutoff relay if needed) to help prime the system.
- Start the engine and keep it at low idle.
- Leave the joysticks alone for a few minutes. Let the system push trapped air back into the tank.
- Shine a flashlight under the machine and look for leaks.
- Slowly move the loader arms up and down and tilt the bucket back and forth.
- Check the fluid level again. It will drop once the new pump and filters fill with oil. Add more fluid if needed.
Troubleshooting Common Post-Installation Issues
- The pump makes a loud whining sound: This normally means cavitation (air inside the system) or not enough fluid reaching the pump. Shut the machine off right away. Check your fluid level. Make sure the big suction hose running from the tank to the pump isn’t kinked or pulling air in through a loose clamp.
- Machine moves slow or jolts: Air is still trapped inside the cylinders. Fully raise and lower the loader arms and tilt the bucket several times to push that air back into the reservoir.
- Fittings are leaking: You probably pinched the O-ring during installation, or the fitting didn’t seat properly. Loosen the fitting, check the O-ring. Swap it out if it’s squashed or ripped, then retighten.
Frequently Asked Questions
How long does it take to replace a skid steer hydraulic pump?
An experienced mechanic can swap a basic gear pump in 2 to 4 hours. If you’re a DIYer working on a complicated tandem hydrostatic pump assembly, plan for a full weekend. Take it slow — being clean and precise matters more than rushing.
Do I have to drain all the hydraulic fluid to change the pump?
It depends on where the pump sits compared to the fluid level in the tank. But if your old pump broke down, it probably contaminated the oil. It’s smart to drain the whole system. Flush it if you find metal debris, then add new fluid and filters.
Can I rebuild my hydraulic pump instead of replacing it?
Yes. Most gear and piston pumps can be rebuilt. A rebuild normally runs 40 to 60 percent of the cost of a brand-new OEM pump. If the inner housing has deep scratches or cracks, the pump is shot and you’ll need a new one.
What happens if I cross the hydraulic lines?
Mixed-up hoses can make attachments run backward. Even worse, high-pressure fluid may get pushed into a low-pressure return port, blowing out seals or cracking the pump housing right away. Always mark your hoses!
Need a Reliable Replacement Pump?
Replacing a skid steer hydraulic pump requires careful preparation, clean working conditions, and the correct priming procedure. Always follow your machine’s service manual to avoid damaging the new pump. FridayParts offers a range of aftermarket hydraulic pumps and other heavy equipment parts to help you find a suitable replacement for your skid steer. Before ordering a replacement, verify your machine’s make, model, serial number, and part number.
