Description

The CAT 34055 is the complete valve replacement kit for 4SF Series plunger pumps. Unlike some plunger kits that service only one cylinder, the 34055 is a “one-and-done” solution—it contains all the components needed to overhaul the intake and discharge valves for all three (3) cylinders (6 valves total).

Compatibility

This kit is the OEM standard for the CAT 4SF direct-drive pump line:

• 4SF Series: 4SF35EL, 4SF40EL, 4SF45EL, 4SF50EL.

• Note: CAT valves are precision-engineered for specific flow rates. While they may look similar to 2SF or 5SF valves, the spring tension and seat diameter are specific to the 4SF frame to prevent “valve chatter.”

Kit Contents

This kit includes 6 complete valve assemblies and their corresponding O-rings:

When to Replace (Symptoms)

• Pressure Fluctuations: If the needle on your pressure gauge is “fluttering” or bouncing rapidly, a valve is likely chipped or stuck open.

• Low Pressure: If the pump is running smoothly but simply won’t reach its rated PSI, the valves may be “washed out” (eroded).

• Manifold Vibration: An uneven “thumping” sound often indicates that one of the six valves has a broken spring or debris trapped inside.

• Loss of Prime: If the intake valves aren’t sealing, the pump will struggle to pull water from a tank or tap.

Installation Pro-Tips

The “Suction vs. Discharge” Rule: In the 4SF series, the intake and discharge valves are often identical. However, the orientation is reversed. When you pull the old valves out, pay very close attention to which way the “cage” is facing. If you install them upside down, the pump will not move any water.

1. Inspect the Valve Seat: Use a flashlight to check the brass manifold where the valve sits. If the brass is pitted or “wire-drawn” (has a tiny groove), a new valve O-ring might not seal correctly, and you may need a manifold repair or replacement.

2. No Metal Tools: Use a plastic or wooden dowel to seat the new valves. If you use a metal screwdriver and nick the face of the valve poppet, it will leak immediately under high pressure.

3. Lubricate the O-Rings: Apply a tiny amount of silicone grease to the valve O-rings. This prevents them from pinching or tearing when you press the valve assembly into the manifold.

4. Check for Debris: While the valves are out, flush the manifold with clean water. Small pebbles or bits of garden hose rubber are the #1 cause of valve failure.