Why is it necessary for a mechanic technician to perform an engine oil and hydraulic oil pressure test when a machine has guages to measure these parameters? Assume the guages are functioning!
probably to see the real pressure with a mechanical gauge... instead of an electronic gauge... which may be giving a false reading... even if you think they are working.. plus I think they test the function of different circuits of the hydraulics..
Thanks. Makes sense.
I know that the electronic hyd pressure reading on some machines dash units can be different than if you put on a manual gauge, not much but a gauge will give you a more accurate reading!
each attachment on the machine, needs to operate at a certain hyd pressure, when times goes by, the pressure, get slower,,, that way, the pumps and motors ran very smooth and helps with the operations of the machine.
Testing engine oil pressure with a mechanical gauge is usually to confirm the dash gauge reading or to check pressure at a specifc part of engine. On HEUI engines there is a low pressure circuit for lubrication like all engines and a high pressure circuit to provide the energy needed for the fuel injectors to fire. They both need to be checked to trouble shoot different problems. In hydraulics there can be many different circuits that have pressure and/or flow at different times. A technician needs to be able to check and see if the pressure is at the level it needs to be(relief settting and pump output). He also needs to be able to measure pressure drops across a valve or actuator. Valves will open and close and allow flow during different times and a technician needs to be able to use gauges to see when and at what pressure circuits are powered. A technician also needs to measure air pressure, fuel pressure, transmission pressure,vacuum, boost, and clutch pressure. One thing that people seem to always over look is that pressure dosent always tell you the whole story, especially in hydraulic systems. Flow is a very important consideration when troubleshooting and makes the difference between mindlessly changing parts and being able to prove a faulty component.
Engine oil pressure tests I have only done when the machine indicator or gauge is not functioning properly. Usually the machine gauge indicates little pressure at low idle of the engine so to be safe I'll check it with my gauge because mine has been calibrated against a known standard. There are many hydraulic pressures on most machines. The only pressure indicated in the electronic system is the main operating pressure. I have found over the years that the electronic indicators are about as accurate as the gauges. The hydraulic system on an excavator may have two pump main pressures with the associated control pressures. There will be pilot pressure and then all the individual circuit relief pressures. Power shift transmissions have main pressure, clutch pack pressures and torque converter outlet pressures. You will also have steering and brake pressure on a dozer. All these readings have to be interpreted in context with the factory specifications. Most owners never need all this technical information and if the need does arise they can find a qualified mechanic with the right tools to figure it out.