Imagine driving a car without a speedometer or repairing electrical wiring without a multimeter. Trying to diagnose a fault in an excavator or tractor without the right equipment is exactly the same. You replace the pump, seal the control valve, buy a new hydraulic cylinder, and the machine still doesn't have the power to lift a load? Experts at BRhydraulic explain how to stop guessing and why a diagnostic kit with a pressure gauge is an investment that pays for itself with the very first failure.
1. Why does "guesswork" diagnosis cost thousands of zlotys?
The hydraulic system is a closed system of interconnected vessels. When a loader arm suddenly drops or loses lifting capacity (as we wrote about in previous articles), there is one symptom, but several potential culprits. It could be a worn pump, a broken spring in the relief valve, a scratched control valve spool, or internal cylinder seals.
Buying and replacing parts "blindly" through trial and error is the most expensive form of maintenance. Connecting a pressure gauge allows you to locate where the system is losing vital pressure in just a few minutes, saving you time and a lot of money on misguided purchases.
2. Test ports – where to look for the machine's pulse?
To measure pressure, you need to know where to connect. Modern agricultural and construction machinery (as well as many high-quality control valves) come factory-equipped with so-called test points.
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These are small fittings (most often Minimess standard, e.g., with M16x2 thread) equipped with an internal check valve.
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They allow you to safely screw in the pressure gauge hose even when there is oil in the system (always do this with the engine off and the equipment lowered!).
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In older systems without test points, measurement requires inserting a tee with a pressure gauge outlet directly into the supply line (e.g., between the pump and the control valve).
3. Cold and hot test – how to read the results?
Simply connecting the gauge is only half the battle. How do you perform a basic health check on the pump and the relief (safety) valve?
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Cold start: Connect the pressure gauge to the supply line. Start the machine (the oil must be cold). Idle pressure should be relatively low.
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Maximum load: Actuate any control valve function to its limit (e.g., close the bucket completely) and hold the lever. At this point, you force the main relief valve to open. The pressure gauge will show the maximum pressure the system can generate (e.g., 180 bar).
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Test after warming up: Repeat the same test after 30 minutes of heavy work, when the oil heats up to 50-60°C. If the pressure drops drastically with hot oil (e.g., from 180 to 120 bar), you have solid proof that the pump is worn and is bypassing thinned oil (or the relief valve is faulty).
4. Choosing equipment: only glycerine-filled dials
In hydraulics, pressures change in fractions of a second, generating powerful pulsations and vibrations. If you use a standard "dry" pressure gauge, its needle will jump so fast that you won't be able to read the result, and the clock mechanism itself will be destroyed. This is why glycerine-filled pressure gauges are the absolute standard. The dense liquid inside the dial dampens the needle's vibrations, ensuring a precise reading and protecting the delicate gears from sudden pressure spikes.
Diagnosing a failure doesn't have to be a guessing game, and correct measurement is the foundation of professional service. Specialists at BRhydraulic.eu will help you select ready-made diagnostic kits, reliable glycerine-filled pressure gauges, as well as hoses and test ports, which will allow you to pinpoint any fault accurately and independently, avoiding costly "blind" replacements.
