How to Replace Graco Pump Packings: Complete Step-by-Step Rebuild Guide

Replacing the pump packings on a Graco airless sprayer is the single most important maintenance task you can perform — and it is well within reach of any contractor with basic hand tools and 45 minutes. When done correctly with OEM parts, a packing rebuild restores your machine to factory performance, extends cylinder life by hundreds of hours, and costs a fraction of what a service centre charges for the same job. This guide covers every step: when to rebuild, what you need, how to take it apart, what to inspect, and how to put it back together correctly the first time.

Before you buy a kit or pick up a wrench, run the motor cycling test. This takes 60 seconds and tells you with certainty whether packings are the problem or whether you should be looking elsewhere.

Get the Right Kit Before You Start

Lay everything out before you start. You do not want to be hunting for a wrench with packings soaking in a cup of oil.

Step-by-Step: Pressure Relief and Flush

1. Engage the trigger lock on the gun.
2. Turn the pressure control knob to its lowest setting.
3. Switch machine to PRIME mode. Place the drain tube into a bucket.
4. Disengage the trigger lock. Point the gun into the bucket and pull the trigger to release all remaining pressure. Hold until fluid stops.
5. Re-engage the trigger lock. Turn the machine OFF and unplug it.
6. Place the suction tube in a bucket of clean water. Flush the entire fluid section until the water runs clear. This removes paint from the cylinder bore, piston rod, and sleeve — making disassembly much cleaner.
7. Once flushed: relieve pressure again via the gun trigger into a bucket. Unplug. You are ready to disassemble.

Removing the Pump From the Machine

1. Disconnect the suction tube — unscrew the jam nut at the base of the pump by hand (use groove-joint pliers if needed). Pull the tube straight down.
2. Disconnect the outlet hose coupling from the top of the pump. Have a rag ready — residual fluid will drain out.
3. On models where the pump is retained by a mounting clip or bolt (Ultra Max II, FinishPro), release the clip or remove the bolt. The pump should slide or lift free from the drive housing.
4. Carry the pump to a clean, well-lit work surface. Set it upright. Do not lay it on its side during disassembly — small parts and balls will roll.

Work methodically. As you remove each component, lay it in order on a clean rag from left to right — this makes reassembly far easier and eliminates the chance of reinstalling packings in the wrong sequence.

Part A — Remove the Packing Nut and Throat Packings

1. Using the 1-1/4" wrench or adjustable wrench, unscrew the packing nut (the large hex nut at the top of the cylinder). Turn counter-clockwise. It may be tight — use a firm, controlled turn, not a jerk.
2. Once the nut is off, remove the O-ring from the packing nut. Discard it — the 18B260 kit includes a new one.
3. Slide the piston rod up and out of the top of the cylinder. It will bring the sleeve and piston assembly with it on some models.
4. Flip the cylinder upside down over your work rag. Use a flathead screwdriver handle (not tip) and rubber mallet to gently tap the throat packings and glands down and out. They will fall free in a stack. Note their order and orientation — photograph this before disturbing the stack if you want a reference.
5. Discard all throat packings and glands. Do not reinstall any of the old packing material.

Part B — Remove Piston Packings from the Piston Rod

1. Hold the piston rod steady — clamp the rod in a vise at the drive rod connection point (use rag padding to prevent jaw marks) or use a 9/16" wrench on the flat section of the lower piston rod.
2. Using the 9/16" wrench, unscrew the piston valve bolt (the bolt at the very bottom of the piston rod) counter-clockwise. Note: this bolt has a thread-locking patch from the factory — it will resist initially. Apply steady torque.
3. Tip the bottom of the piston rod over a clean surface and allow the piston ball to fall free. This is the outlet check ball — keep it safe or replace it with the new ball in the 18B260 kit.
4. Slide the piston packings and glands off the piston rod. They may require pliers if they've compressed over time. Lay them in order on your clean rag.
5. Discard all piston packings and glands.

Part C — Remove and Disassemble the Intake Valve

1. Using groove-joint pliers, unscrew the intake valve housing from the bottom of the cylinder. Counter-clockwise.
2. Tip the intake valve upside down over your rag. The inlet ball will fall out — catch it or replace with the new ball from the kit.
3. Use the pick tool to remove the O-ring, seat washer, and seat from inside the intake valve body. The seat is reversible on most models — if the side facing up is worn, the other side can still be used.
4. Clean the intake valve body thoroughly with the nylon brush and clean water. Inspect the seat — if both sides show pitting or scoring, replace it. The 18B260 kit includes a new seat.

This is the step most people skip — and it's the reason many rebuilds fail within 30 days. Installing new packings into a scored cylinder or onto a damaged piston rod does not restore performance. The new packings cannot seal against a damaged bore. Inspect carefully before you reassemble.

Inspect the Cylinder Bore

Hold the cylinder up to a bright light and look inside the bore. You are looking for:

Inspect the Piston Rod

Run your fingernail along the chrome piston rod surface in the area that travels through the packings. Any roughness, rust, or visible scoring means the rod has been damaged by dried paint abrading against it. A damaged rod will destroy new packings within weeks.

By now the leather packings have been soaking in SAE 30W oil for at least an hour. The cylinder bore and piston rod are clean and confirmed undamaged. Work slowly through these steps — the sequence and orientation of packings matters.

Part A — Install Piston Packings

1. Lightly grease the new piston packings using the break-in lubricant included in the 18B260 kit — or a thin film of petroleum jelly. Do not over-lubricate.
2. Slide the piston packings and glands onto the piston rod in the correct sequence. Refer to your photo from disassembly or the diagram sheet inside the 18B260 kit packaging. V-packings face the correct direction — lips pointing toward pressure (downward on the piston rod).
3. Install the new piston ball into the piston valve bolt seat. Apply a small amount of the included thread sealant to the bolt threads — do not get any on the ball itself.
4. Thread the piston valve bolt onto the piston rod and torque to 25–30 ft-lbs. Under-torquing allows the bolt to back out under operating pressure. Over-torquing crushes the thread lock patch and can strip the rod.

Part B — Install Throat Packings into the Cylinder

1. Lightly grease the inside of the cylinder bore and the new throat packings.
2. Install the throat packings and glands into the cylinder in the correct sequence — alternating leather and V-packings per the diagram or your photo. Press them in firmly and evenly; they should seat flush.
3. Grease the O-rings on the sleeve and slide the sleeve into the bottom of the cylinder.
4. Grease the top 1–2 inches of the piston rod and slide the piston rod assembly up through the bottom of the cylinder. Guide it carefully — do not damage the new packings by forcing the rod.
5. Install the new O-ring onto the packing nut. Thread the packing nut into the top of the cylinder by hand, then torque it to 140 ± 10 in-lbs (approximately 12 ft-lbs). Do not over-tighten — this compresses the packings against the rod and if over-tightened will cause premature wear.

Part C — Reassemble the Intake Valve

1. Install the new O-ring into the intake valve body.
2. Install the new seat — if reusing the old seat, flip it to use the unworn side.
3. Drop the new inlet ball onto the seat.
4. Thread the intake valve back into the bottom of the cylinder. Torque to 50–60 ft-lbs.
5. Reinstall the pump into the machine, reconnect the suction tube and outlet hose. Ensure all connections are hand-tight plus one quarter-turn with the wrench. Do not over-torque hose fittings.

New packings need a short break-in period to seat correctly against the cylinder bore and piston rod. Do not run straight to full operating pressure — the break-in run prevents premature packing damage and confirms the rebuild is leak-free before you load paint.

1. Fill the TSL wet cup completely full of Graco TSL.
2. Place the suction tube in a bucket of clean water. Set the pressure control to its lowest setting.
3. Switch to PRIME. Turn the machine ON. Let it run on PRIME for 30–60 seconds at low pressure — this works water through the new packings and seats them gently.
4. Switch to SPRAY. Install a tip and gun filter. Slowly increase pressure over 2–3 minutes to full operating range. Do not immediately crank to maximum.
5. Spray clean water into a bucket for 2–3 minutes at full pressure. Watch the packing nut area — there must be zero paint or fluid at the packing nut. A small amount of TSL weeping is normal during break-in; paint or water is not.
6. Release the trigger. Count motor restart interval — should be 15+ seconds. If it is, the rebuild is successful. If not, recheck the packing nut torque and the intake valve assembly.

While You're In There — Parts Worth Replacing at the Same Service

You've already got the pump apart. Adding these parts to the same service costs 20 extra minutes and eliminates the failure modes most likely to bring the machine down again within the next 100 hours.

Frequently Asked Questions