Hydraulic Pressure Relief Valve Constantly Dumping: What It Means and How to Fix It

If your hydraulic system is losing power, building heat, or acting sluggish — and the pressure relief valve is constantly bypassing fluid — you’re dealing with one of the most overlooked yet critical issues in hydraulic diagnostics. A relief valve stuck open or constantly dumping kills pressure, wastes energy, and can damage pumps and components over time.

What a Relief Valve Is Supposed to Do

The pressure relief valve protects your hydraulic system from overpressure. When system pressure exceeds a safe limit (usually set by the manufacturer), the relief valve opens briefly to divert fluid back to the tank. Once pressure normalizes, it closes again. This process should be momentary — not constant.

When the Relief Valve Is Always Dumping

If your relief valve is stuck open or continuously leaking fluid, you’ll see symptoms like:

  • Weak hydraulic performance or low force during lifting or extension
  • Pump continuously running under strain with little to no output
  • Fluid heating up quickly, even under light use
  • Audible hissing or bypass sound at the valve or return line

What Causes Relief Valves to Stay Open

  • Contamination: Debris stuck in the poppet or seat prevents the valve from sealing completely
  • Spring failure: A broken or weakened spring can’t hold the valve shut at set pressure
  • Improper pressure setting: If the valve is set too low, it opens during normal operation
  • Worn or damaged sealing surfaces: Age or repeated use degrades sealing ability, causing leakage
  • Misapplied valve for the system flow or pressure: Underrated valves may dump prematurely or fail entirely

How to Diagnose a Dumping Relief Valve

  1. Install a pressure gauge at the system’s main circuit and monitor pressure during operation
  2. If pressure peaks below normal operating range and fluid returns to tank, the valve is likely dumping
  3. Temporarily block or isolate the relief valve (using safe manufacturer-approved methods) to confirm it’s the source
  4. Disassemble and inspect the valve for metal chips, broken springs, or erosion of the seat

Repair or Replacement?

  • Clean and reseat: Minor contamination can sometimes be cleared by cleaning the valve internals
  • Replace the spring or sealing elements: Most valves can be rebuilt with OEM kits
  • Replace the valve: If scoring, erosion, or mismatched specs are found, a new valve is the best long-term solution

Preventing Relief Valve Failures

  • Change hydraulic filters regularly to prevent contamination buildup
  • Use fluid with correct viscosity and additive package to reduce wear
  • Never exceed the designed system pressure or modify settings without verification
  • Install a gauge permanently to monitor system pressure trends

Conclusion

A relief valve that’s constantly dumping is robbing your system of pressure and damaging components over time. Accurate diagnosis — not guesswork — is key. Whether it’s contamination, spring failure, or misapplication, correcting the issue restores full hydraulic performance and protects your entire system from premature wear and energy loss.

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